Send any comments to the maintainer Roger Caffin
Bushwalking is great fun, but by the end of the day you are going to be tired. You won't have a whole lot of light, and no TV either. You are going to be asleep for up to 12 hours: half the day. You're doing this for fun (remember that!), so you might as well be warm and comfortable for those 12 hours. Anyhow, there's nothing like getting out of the bad weather, drying off and climbing into a nice warm sleeping bag at the end of a hard day. And a good night's sleep is what you need if you are going to be fit for the next day. Sleeping on cold hard lumpy ground is not fun though, and trying to sleep on snow is even worse, so some form of padding or mattress under you is also necessary. This can be just for insulation, if you are utterly insensitive, or also for padding for comfort. So sleeping bags and mattresses are a very important part of your gear.
Like everything else in this game, sleeping bags come in a range of shapes and qualities, and Ygwypf. They come in a variety of shapes, fabrics and fillings. Fortunately, our good Australian manufacturers are easily on a par with the rest of the world when it comes to quality. And they give us quite a few brands and styles to choose from. There are some other cheap types on the market which aren't worth taking bush, but we'll cover those too.
The purpose of a sleeping bag is to keep you warm at night. However, it won't make you warm: it will only slow down your heat loss. Any energy, heat or warmth has to come from your body. If you are cold or exhausted, you may not get very warm, without energy. If the bag is not warm enough, or doesn't have enough insulation, you may still be cold. At the very least you have to eat enough to help your body generate heat to keep you warm through the night. Of course, in summer time it may be warm enough to sleep on top of your bag for most of the night: under these conditions a lighter bag would easily suffice, but I still recommend the dinner. And you will need some sort of insulator under you, because lying on the insulation in the bag squashes it so it no longer insulates very well. The ground can be cold. Some of what follows applies more to bags for winter conditions, but can be applied to lightweight bags in summer when it is cold.
An interesting question is just how old is the idea of a sleeping bag? To be sure, people have used furs and then blankets and so on to keep warm ever since we lost our fur, but the question here is about the idea of a bag. Not so long ago is the answer: in 1861 one Francis Fox Tuckett built and tested his prototype alpine sleeping bag. A few years later in 1865 the English mountaineer Wymper made the the first ascent of Matterhorn. It is also interesting that some of the ealiest insulators used were woven camel fur and then kapok. Only later was duck/goose down introduced. Anyhow, around 1890 Ajungilak of Norway started the first commercial production of sleeping bags. Since most readers weren't born then, this may seem like a long time ago. It is interesting that means for the measurement of sleeping bag insulation were being developed as early as 1942, under funding from the US military. On the other hand, actual Standards had to wait until the 1990's, when American, French and European Standards came into existance. Naturally, these different Standards did not give the same ratings: they all had slightly different test conditions. What is interesting is that more recent work on a European Standard, EN13637, has shown that there are consistent significant national differences between ratings from manufacturers. Sadly, it would seem that the American bag makers all claim at least 10 C better performance for their bags than any other country/Standard would allow: you have been warned! A very interesting review (pdf) of both the history and the current European Standards work is given by the Swiss company Mammut. My thanks to Aushiker and Alex Tweedy for this reference.
When you buy a sleeping bag you have to make sure it is warm enough, long enough and wide enough. I am told women need a different shape of sleeping bag from men. An interesting thought, but it may be ignored for now. More to the point, it seems that women in general need a sleeping bag which is 5C warmer than men. Not so obvious is that older folk may also need a warmer sleeping bag than men in the 20-40 age group. However, an equally significant variation is caused by the experience of the sleeper: a hardened walker or mountaineer will always seem to be far more comfortable than a complete novice. On the other hand, if you just want the bag for summer use you should not be looking at snow-rated bags.
While on the subject of warmth can I recommend being very friendly with your tent partner? There is nothing quite like snuggling right up to keep you warm. If you are lying on any reasonable sort of mat your lower side is probably warm enough. If you can add a heater all down one side, that leaves only the top and other side for heat loss. It makes the night so much more comfortable. Of course, it means you both have to turn over at the same time, but you are usually aware of when the other person turns over anyhow. It is then interesting in the morning to see where you are relative to the centre line of the tent. Who chased who in the night?
To check the size ask to try the bag out in the shop. The staff should be happy to let you try getting into one briefly, provided you have clean clothes and have taken your shoes off. If they won't, go elsewhere. Make sure your feet do not touch the end of the bag when your head is well down inside - maybe when your nose is level with the front of the opening. Make sure there is enough room that you won't be sleeping with the bag stretched tight over your knees or your backside. That will compress the down, even with "differential cut", and reduce the insulation. It may be necessary to readjust the bag during the night to keep all of it slack, but you get used to that. In snow conditions you may need some extra space at the foot end. More than once I have stored both my ski boots (in plastic bags of course) and my water bottle inside the foot of my sleeping bag in the snow. At least I could put the boots on the next morning, and not have instantly frozen feet from it. I have also resorted to keeping my contact lens kit in my sleeping bag sometimes after I found the poor things frozen solid one morning. If you have a warm breakfast, keep your butane lighter with you too!
The hood of your bag is going to be important if you are using the bag in cold weather or in the snow, so hoods get their own section below. At this stage let's just say there should be a hood of some sort for all but summer bags used in hostels, and the hood should be of a generous size.
Most people probably know to not sleep on top of the zip, especially the slider. It can be painful, and the same goes for any toggles on the cord around the hood. You may find it a good idea to make sure there is enough room in the bag to avoid the zips and toggles, or to consider removing the toggles completely. You can always tie a slip knot instead of carrying the extra weight of a toggle.
In looking at the different designs below, keep one thing in mind. While a 'bag' is the conventional design from 1890, it is not necessarily the only design. When you sleep in a bg, all that section under you is wasted: your body weight squashed the down flat so it cannot insulate. Try sleeping on cold ground for a little while and you will appreciate the truth of this. You don't sleep in a bag at home: many/most people these days sleep under a doona. Curious: why the difference?
Finally, you may see a few bits of down floating around in the morning. Don't worry too much about this, and read the fabric section below.
Mummy: Shaped like an Egyptian mummy, with a zip down the side. The shorter the zip, the better: less weight and less heat loss. Usually designed for the coldest conditions, snow and ice, and with a good hood and neck muff. Australian mummy designs have more sideways leg room than American ones, which seem incredibly narrow. Maybe Yanks have no leg muscles?
Tapered: Not as shaped as a mummy bag. The zip may go to the bottom, and some models may have another zip across the bottom, to let them open out as a quilt. Alternately, you can zip two similar bags together (but this rarely works very well in practice). The bottom zip is excess weight in my opinion. At least one manufacturer agrees with this comment, but says the market still asks for it. Still designed for fairly cold conditions, and with a fairly good hood.
Rectangular: This is designed to open out into a quilt, with zips down the side and across the bottom. The design is unreliable in the cold, but these bags are not meant for really cold conditions anyhow. Most have a hood, but not all. Suitable for warm conditions (Northern Territory in summer) and travel.
Single sided: This is a variation on the rectangular design. In the interests of saving weight only the top half of the bag has baffles and down in it. The bottom of the bag is either a sleeve into which you insert your sleeping mat or just a single layer, like a sheet. There is some weight reduction in this design, but not everyone finds the result adequate. However, the reasons people have trouble with this design are varied. If you try to treat it like an ordinary bag, you may have some problems. In addition, with the weights you find with some older shells, leaving just the down out is purely a cost-cutting exercise: it doesn't save much weight. Skip forward to the Quilt design below.
Double width bags: Sounds a wonderful idea (hint, hint), doesn't it? But in practice, there are complications, especially in the snow with conventional designs. For a start, in general you cannot get the separate hoods to do up around your heads very well. There are drafts in the gap between the two of you. If one person sits up in the night for any reasons, the other person gets cold. A double-width liner is a disaster: the liner tends to stick to your sweaty skin, and after one person turns over you are both tied up in knots in the liner. Still, have fun trying. On the other hand, if you have separate liners a double bag may still work if it is not very cold. On the other hand, a double-width quilt is just the same as a doona at home.
Lightweight bags: This doesn't refer to cheap supermaket bags but to specialised bags made for experienced walkers, usually with very high quality materials. After all, you don't always have to carry a -30C snow bag with 900 gms of down. They can come in a variety of shapes, and are sometimes sold as liner bags for really extreme conditions. We have used a Mont Nitro bag with only 150 gms of down at temperatures down close to freezing. When it got very cold we wore thermal tops inside these bags, and my wife and I slept snuggled together for extra warmth.
More recently I made my own shells out of Pertex Microlight fabric. The shells weigh about 250 grams: a far cry from the 850 grams you find in some Australia bags of the older vintage. And I put 300 grams of 800 loft down in the shells: better than the cheaper stuff found in many Australian bags. My wife and I have used these bags across the Pyrenees in summer, in NSW in the thrtee warmer seasons, and even in Kosciusko NP when it went sub-zero over night. We were OK with thermals and snuggled up. You can get imported bags like this, and One Planet have started (mid-2006) making some commercially - the Cocoon series. Don't try going this lightweight unless you know what you are doing.
Quilts: I distinguish between single-sided bags and quilts for good reason. A quilt is really meant to function like a doona on your bed, not as a bag. Your mat, be it foam or inflated, provides the insulation under you and the quilt goes over you. This puts the insulation where you need it - and dispenses with the weight of zips as well. "What about a hood?" you might ask. Well, the bit of the hood between your head and your pillow does nothing. It's squashed flat, and wasted. What do you do at home? You pull the doona over your head. What did people do in the old days before central heating? They wore a bed cap. What do I do? Both, in fact. I have a fleece hat I wear in bed, and if it's cold I pull the 'hood' part of my sleeping bag over my head. This is because I use my Pertex-shell sleeping bag as a quilt, on top of me. This works down to sub-zero conditions with 300 grams of down.
Now to get very clever. For very cold weather - like seriously sub-zero in the snow, we now take our light Pertex-shell bags plus a 930 g quilt (shell 330 g, down 600 g). My wife and I sleep snuggled up with our individual light Pertex bags with the quilt over the two of us. There is enough insulation from the two layers to keep us warm, but in addition I have a heater with me under the quilt: my wife. The total mass of the two bags and the quilt is 2.05 kg, while the combined weight of our two old conventional snow bags was 3.36 kg - and we are warmer.
The outer cover of the sleeping bag is called the shell. It has to hold the down inside while being as light as possible and breathing out water vapour really well. This usually requires a really fine tight-weave synthetic fabric, and there are not too many manufacturers in the world who can make this well. The brand "Pertex" is very well known one here: it came from Perseverence Mills in the UK (now owned by Mitsui in Japan). They were arguably the first firm to produce such specialised fabric for sleeping bags. There are some very fine Japanese fabrics as well, but I know less about them.
A feature of all sleeping bags (and down clothing too) is that the fabric does not absolutely stop every last bit of down from escaping. You will find the odd little feather floating around your tent in the morning. Some people get upset about this, but it really does not matter. There are probably billions of downy feathers inside the bag: the loss of a few makes no difference at all. Yes, it could be prevented, but only by doubling or tripling the weight of the fabric. Anyhow, what gets out usually comes out the stitching holes, not the fabric, unless it was actually a feather rather than a down plumule.
For some reason (mainly associated with some serious marketing efforts as opposed to any logic imho) some manufacturers have switched to a Gore-Tex fabric called DriLoft for the foot of the bag, or even the entire outer shell. This fabric is supposed to be as light as Pertex and breath as well as Pertex but be waterproof as well. There are other membrane fabrics used these days too. The logic is that you can get drips of water from the inside of your tent in very cold weather, or from your snow cave, and these are going to make your bag very wet. Too many drips certainly can impact the warmth of a bag, although by how much is another question. But the DriLoft fabric is heavier than the light Pertex fabrics and much dearer, so there is a definite trade-off. The trade-off gets worse when you consider what happens on the inside of the bag. Gore claim their DriLoft fabric breathes moisture as well as many ordinary fabrics, but this is under their chosen test conditions. These just could be optimised to suit their fabric of course.
In practice, DriLoft does not work so well under most conditions. Because it has a membrane it does not allow air to pass through, while ordinary fabrics do. So ordinary fabrics will allow far more real breathing when you take into account your thrashing around inside the bag. In addition, the distinct barrier the Gore membrane creates can encourage far more condensation on the inside surface of the cold outer shell, and once this starts to happen the breathability of DriLoft goes right down for technical reasons. If this happens to ordinary fabric the moisture wicks through to the surface and evaporates off fairly quickly. In fact, it is quite possible for some of this water to turn into ice on the inside of your bag, especially if the air on the outside is way below zero. Coated fabrics like DriLoft have been found to be more prone to this than uncoated fabrics: they get an ice build-up just inside the outer shell more easily and more often. The extreme version of this is experienced in the Antarctic, where sleeping bags used to be rigid with ice after a while.
Is it worth the extra cost and weight to have the DriLoft (or other brand) fabric? Not really, not unless you are going into extended snow cave camping. Even then, a good water-repellent coating is more effective. You may find that New Zealand sleeping bags cater more for snow caves: good bags I'm sure, but not as suitable for Australian conditions.
If you do have a sleeping bag with one of these waterproof shells, you will find it quite hard to pack. The air gets caught inside the bag and can't blow out through the fabric. The simple solution is to turn the bag inside out before you pack it, and/or to pack it from the foot region first. And make sure you air it inside out as often as possible.
The filling in a good sleeping bag is either down, which in the good Australia brands ranges from good to very good, or a synthetic such as Qualofill or Polarguard. The filling in cheaper sleeping bags is usually a cheaper synthetic, and once again ygwypf. We won't mention the venerable kapok from the middle of last century, let alone the old Army blanket with blanket pins (ah, memories).
The thing to understand about the filling is that the material used (be it down or synthetic) does not provide the warmth. It is the air trapped in the filling which keeps you warm. So you want a filling material which traps the most air for the least weight. Down is still the best material for this: those birds have been at it for a long time. But some of the latest synthetics are not bad, and they do have some advantages.
What is 'down' really? I will paraphrase from an excellent discourse by Ted Ripley-Duggan in a review of a Bask sleeping bag at BackpackGearTest in this and the next section.
Down is feathers, right? Well, no. Down is the undercoating of waterfowl, as distinct from feathers. Each fragment of down is called a plumule, and grows from a single quill point, rather than a shaft, as a feather does. For sleeping bags, those waterfowl may be geese (gray or white) or ducks. Chickens need not apply. Traditionally, goose down has been preferred for sleeping bags, but there's a battle-royal between advocates of duck down and goose down that goes back a good thirty years to my knowledge (see Backpacker, issue number 2 for a fierce debate, and that's Summer 1973), and no doubt considerable longer than that! Suffice it to say that both can be excellent, if correctly prepared.
Down grown on cold-climate birds tends to be better than that of birds in warmer climates. Other factors enter into the equation, though, including the diet of the animals, the de-pluming method, etc etc almost ad infinitum. Also, most down is not "undercoat" alone; there's an admixture of feather, measured by weight. Bask offers a number of such blends; that used in the present bag consists of 85% grey goose down and 15% goose feather. This provides a fill power [or loft] of 650 in this case.
The better quality down comes from the more mature birds. The down on very young birds has not had a chance to reach its full stregth, and will degrade more quickly. However, there are only so many wild birds available, and most down comes from ducks and geese grown commercially. They are usually 'harvested' before they are fully mature - for food. The down is a by-product. Some down comes from Eastern Europe, but a lot of it comes from Asia and especially China. They eat a lot of duck there. But the best down is obtained from the nest of the wild (protected) Eider duck after it has hatched its babies each year. This is 'Eider down', and it is rare and very expensive.
Two things can reduce effectiveness of the down in a sleeping bag. The first is a general breakdown of all those little bits of down. This happens slowly with age, but it can be greatly accelerated by leaving the bag compressed for most of the year in your cupboard. Poor little bits of down: they weren't meant to take that treatment. The duck's answer is to grow new down all the time. The human equivalent is to replace the down filling when it degrades too far, but this is best done by a specialist. Unless you have tried it, you have no idea of how far a few grams of down can go in your living room! To prevent the breakdown of the down you should store your bag in a very loose cover which lets it stay "lofted". The other hazard for down is damp. This is discussed below.
What's fill power [or loft], you ask? Well, in order for down to be effective as an insulator, it has to trap air. In a sleeping bag, it's mostly that trapped air that keeps you toasty. Sleeping bags function by minimizing the escape of the body's own heat. Fill power is a measure of the ability of down to expand after compression; the more the down expands, the higher the fill power of the down, and the more effective an insulator it is. Fill power is calculated using a gauge (and there are several types) that compresses the down by a standard amount, and then lets it expand to its full extent. The technology is (naturally) more complex then that, but in essence, that's what fill power measures. The number represents the number of cubic inches to which one ounce of down will expand after compression, under defined conditions of temperature and humidity. The bigger the number, the more trapped air, and the better the insulative qualities of the down.
However, some manufacturers of sleeping bags have used the term slightly differently. They use it to mean the height to which an uncompressed sleeping bag will expand. Generally this is measured from the ground to the high-point of the baffle. While this certainly is a very relevant use of the term, it is not subject to a Standard and does not tell you much about the actual down itself. It may tell you something about the warmth of the bag in the field. You will need to check which meaning is being used at any point.
It seemed that every manufacturer in Australia once had a slightly different way of defining loft - or so they claimed, to avoid comparisons. However, most do now use the first definition. Typical loft values (or fill power) seem to range from 600 to 850. They may not all be exactly the same, but it is possible to rely on the brand reputation here in Australia rather than to worry too much about the numbers.
The problem with this measurement system lies in the lofting process. If you let the down loft up by itself, it will of course rise so far. What happens if you fluff it up a bit? It isn't hard to imagine that the volume might increase a bit. So what is permitted? Following on from that, it isn't hard to imagine that the diameter of the cylinder may have some influence on the result. A narrow cylinder will have lots of drag between the walls and the down, while a wide cylinder will have less. Are all measurements made under exactly the same conditions? One hopes so.
That much said, we can give some rough rules. 600 loft down is fairly cheap, while 700 loft down is usually the 'good' end of the spectrum. One does not see lower loft being quoted very often. Going upwards, 800 loft down is getting quite expensive, and one has to ask how long it will stay at 800 loft. I have even seen 850 loft being quoted, but I have reservations about the significance of any difference between 800 and 850 measurements in practice.
You will also see some vendors quoting figures like '90% down, 10% feathers'. Ted mentions this above. While true, this is generally less useful. You simply can't separate all the feathers out from the down, some some little feathers do get included. Too many feathers and the insulation will go down, weight for weight, but I have also heard claims that down needs some small feathers to help it fluff up. This may be true - I don't know.
Fairly recently (2005?) someone bitched to the ACCC about the claim by many sleeping bag vendors in Australia that their down was 90% down or 100% down. The ACCC had some bags tested overseas, at huge expense, and found that the figures were not always exactly accurate. The bag makers replied that they conformed to the Australian Standard, which allows a 10% tolerance. Given the difficulties of measuring the fractions, this seemed a fairly tight tolerance. However, the ACCC replied that they didn't care what the Australian Standard said, if it wasn't 100% pure down the makers couldn't claim 100%. Exactly what constitutes 'down' is not that clear anyhow. A whole lot of our Australian sleeping bag manufacturers sighed and entered a consent agreement to change their ways and post a notice on their web sites explaining this. The whole things was a huge waste of time and taxpayers' money of course. Then the consenting SB makers pointed out to the ACCC that there are a huge number of doona and quilt makers in Australia, and that the ACCC now had to test items from every one of those companies as well. The cost (to the taxpayers) escalated. It should be addded that overseas manufacturers all have exactly the same problems of course. Exactly nothing was achieved.
Synthetic fillings try to emulate down by having a mass of very fine fibres all tangled up. The more advanced versions use hollow fibres to reduce the weight. In fact, they do work quite well, but have not caught up with down yet for warmth - until they get wet. One great advantage of the good synthetics is that they can still provide some (limited!) warmth after getting wet. You squeeze the bag out, give it a good shake, and hope to dry it out some more with your body heat. The same synthetic filling is used on ski trousers and even some padded jackets, apparently for this reason. Well, that's the commonly accepted theory, but see below for actual test results.
Synthetic bags also cantake a whole lot more abuse and washing than the down ones. The fibres are usually bonded together into some sort of mat, and can take a lot of rough treatment. Down on the other hand can be broken down by rough treatment like being crushed under shoulder straps for the day. Down also suffers when washed: the natural oils get stripped out, which accelerates its decay. I have a nice down duvet jacket, but I don't wear it while I have a pack on. I would be willing to wear a duvet with synthetic filling.
In addition, synthetics work out cheaper. The filling itself is cheaper because it is made in 'volume'. The fabric used around a synthetic fill can also be cheaper because it doesn't have to be such a tight weave to be "down-proof". This can makes a synthetic bag useful for very wet conditions like snow caves. If you are going trekking or travelling, a synthetic bag may be worth considering as well. However, they will be heavier and they will be bulkier. They are also good for young kids who don't look after their gear so carefully. It is interesting that a lot of the bags sold in Europe are synthetic, but the buyers are usually fairly inexperienced walkers who stay in (heated) hostels and catered refuges.
Then there are the cheap synthetic bags, sold in places like K-Mart and so on for prices like $25. They sometimes even have a brushed cotton fabric inside, in pretty printed patterns. Well, I am sure they have their place somewhere, but ygwypf and I wouldn't even bother thinking about one for bushwalking. Maybe a heavy one might be suitable for car camping in the tropics.
I mentioned above that the popular perception is that the insulation value of down collapses when it gets wet. Well, that's the theory, but is it true, or just a myth promulgated by the manufaturers of the synthetics? This was tested at Backpacking Light, and the results were quite startling. I will quote a small bit of the report "Drying Characteristics of Select Lightweight Down and Synthetic Insulated Tops," by Don Wilson of Backpacking Light.
'The initial loft after soaking showed a dramatic difference between the Flash [down] and the Micropuff [synthetic] vests. When saturated, the loft of the Flash vest dropped to 0.25 inches, losing 87 percent of its dry loft. The Micropuff maintained 0.8 inches of loft, losing only 38 percent of its dry loft. [So far, according to plan - RNC]
A surprise discovery, the down Flash vest recovered its loft quickly. After 30 minutes its loft surpassed the [synthetic] Micropuff. This challenged our perception that a fully saturated down garment is worthless and takes forever to dry. After 40 minutes, both vests had recovered to between 80 and 90 percent of their maximum dry loft. Both vests were at full loft within 80 minutes.
In short, they found that the down jackets did not get as wet, and that the down dried as quickly as the synthetic. It may well be that the down used had retained some of its natural oils, and that this prevented the down from really getting wet. This is a good reason for never dry-cleaning any down gear, by the way. But it does suggets that down gear is more robust than some people make out.
You can lose up to 80% of your body warmth through your head. Come what may, frost bite and the rest, your body will keep your head (and the grey matter inside it) warm. If that means stopping the blood flow to your feet so they get frostbite, so be it. You can be standing out there in a gale, shivering away, and your bare head will still feel warm. What this means in practice is that you can be lying there in your bag feeling horribly cold in the lower half of your body while your head feels quite warm enough. I know how some sleeping bag manufacturers claim they have added extra insulation to the foot box to help keep your feet warm, but that is total marketing hogwash. The problem does not lie at your feet: it lies at your head. The solution is to keep your head warm! That's is what the hood is for.
The conventional way of using the hood is to pull it around your head and tighten the front draw cord. After all, all you really need is a little air hole in front of your nose. Claustrophobia? Maybe so, but being warm all over is much nicer! One thing we can guarantee is that even if you rotate right around inside your sleeping bag, you will NOT suffocate: the material in modern sleeping bags is too thin to allow that to happen (with the obvious exception of bags using DriLoft and similar). Just shut your eyes and you won't notice. If this is how you want to use the hood, then when you buy the bag make sure the hood comes around your face nicely, and that the drawcord is easy to adjust. A shaped hood helps. You should be able to reduce the opening to almost fist size. A good mummy or tapered sleeping bag should also have a neck muff: this goes around your neck to stop cold drafts from going down inside your bag. The muff may also have a draw cord to help block drafts.
A Better Way
However, you don't have to use the hood that way. After all, that leaves a major part of the hood insulation wasted, squashed flat under your head. If you don't have a pillow, the grease from your head is grinding into the hood fabric and the down. Yes, there is another way of using a hood, even in the snow - think doona! Put the sleeping bag upside down on your mat before you get in *. Put your pillow under the hood. Get in, and pull the hood over the top of your head, just like you might pull a doona over your head at home. Your mat and your pillow will keep the underside of your head warm; the hood will flop down over your head and keep it warm too. You might like to have a small fleece ski-cap as well: it stops drafts. Note: you do not have to do up the hood this way, nor do you have to have the bag tight around your neck! You can thrash around under the hood with no problems. You can tuck the hood back a little if you are getting too hot, and you can pull it right over your head if you just don't want to know about the outside world. This happens sometimes! And a lot of your hot breath will stay inside the bag with you, and that really adds to the warmth of your bag.
* This assumes you have a bag which has a uniform thickness of down on the top and bottom. If the quilting goes right around the bag in the conventional manner this should be so. However, some bags have different sorts of quilting, and some even have different amounts of down on top and bottom, or even no down on the bottom. I'll assume you can check this.
"But how will I breathe?" I suggest you do it in the usual manner, through your mouth or nose. But seriously, you simply do not need that much air that you have to have a direct passage to the storm outside. You will quickly find that the loose lay of the hood on your mat will let in enough air for a very satisfactory night's sleep - just the same as at home under a doona. Just make sure there is a little tunnel to the outside world - you need to see when the morning has come after all. And not having the hood done up tightly is so much more comfortable too. Does this work in the snow? Too right, and very nicely too: I have been doing it for years.
A side benefit of the approach is that you may find you need a lighter bag for the conditions. Conventional bags have 700-800 g of down in them; we have used bags with only 150 of down as low as freezing point. Yes, my wife and I snuggled up together, and yes, my wife had her thermal top and pants on, while I had a thermal top. We have used bags with 300 g of 800 loft down slightly below freezing point quite happily - with our thermals on.
Getting into a conventional sleeping bag with no zips is just too hard. You need a zip down to the waist level. But beyond this is another matter. There is a marketing message aimed at the young that having a full length zip means you can zip two bags together. A great idea at first glance, but in reality a complete waste of effort and weight. People simply do not zip their bags together, except maybe in a hostel or similar. Why not? For a start, it leaves a great big opening at the top for cold air to get in. Turning over in a double sleeping bag becomes a major nuisance; sitting up to get a drink in the night becomes even worse. Many of us have tried this and discarded the idea quickly.
Another marketing message is that with a full length zip down the side and another across the foot you can open the bag out as a quilt. Well, get real. You just don't do this with your best bushwalking bag in practice. And doing it with a tapered bag means your feet are never properly covered anyhow.
All you need is a half-length zip. Many good bags go as far as a 3/4 length zip. If the bag you want has more than that, ask if the manufacturer can make you one in your chosen colours and size and with the length of zip you want. The good manufacturers will; skip the ones who won't assist.
The zip is not an insulator. Heat will leak out through it, especially in the winter. So the inside of the zip should have a generous filled baffle tube running the length. Some bags have dual baffles: one on each side of the zip. The baffle(s) should be positioned so it doesn't immediately snag on the zipper: a hard request in fact. Some manufacturers put some heavier material or tape on the baffle where it touches the zip to make it less likely to jam the zip completely, and this is a good idea. But generally you have to be a bit careful when operating the zip to avoid jamming. It gets to be automatic.
Some people claim you should lubricate the zip when you get it. Candle wax or a silicone spray has been suggested. However at least one zip manufacturer (YKK) recommends you do not do this: they say the lubricant collects dirt and actually increases the rate of wear. The message seems to be to keep the zip clean and treat it gently.
What sort of zip is suitable? It seems that we are a rough lot, so a fairly heavy zipper is usually provided. But we don't want it too heavy: we have to carry it. You can get both continuous coil and moulded zips, and both sorts are used. You can different gauges: #3, #5, #8, #10, in increasing size and weight. The #8 size is fairly common for a sleeping bag, but it is rather heavy. The bags I make use #3 zips: I just treat them carefully, and they last for years. The slider should be 'non-locking', or you won't be able to get out quickly in the middle of the night, and it should be 'double-sided' or 'double-pull' so you can open it from the inside and outside. This is normal. A cloth tag on the small pull is a nice idea.
You may see in many advertisements from manufacturers that they only use brand X zips (often YKK) because they are the 'best'. An interesting claim, and not one which has a lot of proof as far as I have been able to ascertain. There are lots of brands available, and one would have thought none of them could afford to let another brand get all that much better. I would be interested in seeing any information to the contrary.
A down sleeping bag is a very large thing when spread out. To get it into your pack you have to stuff it into a bag, often called a stuff or compression sack. The name comes from the compression straps most makers put around the cover sack they supply: you stuff your sleeping bag into this large cover sack and then reef up the compression straps to reduce the volume even more. A convenient idea, but the straps do squash the down and the sack should only be used while you are walking, never for storage.
If you are gong on a short trip and your pack is large, don't bother compressing your sleeping bag. Let it stay a bit loose: it will retain its loft better this way. In fact, some ultra-lightweight enthusiasts in America line their UL pack with their foam pad, then put their UL sleeping bag into the pack, then stuff all the rest of their gear into the sleeping bag. That way their pack, which typically has no structure of its own, gets some shape and their sleeping bag does not get tightly compressed. I am not sure I want to try this in the Australian weather, but you get the idea.
One of the more puzzling things you will see in some books on walking is a picture of your pack with your sleeping bag right at the bottom and your (wet) tent up at the top. If any water gets into the pack from your wet tent, guess where it is going to end up? With a single compartment pack this can be unavoidable, so you will need to get smart here. The heavy compression sack which comes with your sleeping bag is almost guaranteed to leak like a sieve: there is all that stitching through it. When the cover sack is all compressed up, put it into a more waterproof bag. A good plastic bag and a very light nylon stuff sack over that is often used, or a special waterproof sack if you can find one. They add a very small amount of weight, but this is one place where the little extra weight is truly worth while. Such a cover will also protect your bag in your pack when you are walking in heavy rain: some water always seems to get in somehow.
You may see novices walking with their sleeping bag tied to the outside of their pack. This may be OK in the desert (not really: they can get awfully dusty that way), but otherwise it is just plain stupid. The bag will either get soaked when it rains or shredded by the scrub. It could even fall off: we found a sleeping bag lying on a track in the Blue Mountains once: bet he was cold that night! (Pity it was only a cheap bulky sleeping bag.)
A down sleeping bag consists of two bags with down in between. However, if you don't want all the down to collect at the foot of the bag, we have to add baffles at regular intervals around the bag to restrict the movement of the down. These baffles are what gives a bag that curious ribbing which looks like quilting. The baffles do not have to be as strong as the cover material: they are often a very light mesh. That's enough to stop the down moving. However, this mesh can be very light - so light it can be easily ripped if the bag is mistreated, so treat your bag carefully, especially if you have to wash it.
Synthetic bags also have baffles, but these are far less important. The synthetic filling is made from very fine fibres, but these tend to be lightly bonded together somehow, so the filling comes in sheets or bats. However, 'sleeping bags are quilted', so even synthetic bags are quilted. On the other hand, padded ski trousers usually aren't.
Different brands and different models have different baffle designs. The marketing guys make a lot of noise about their special designs, but I don't think there is much between them really - except that increasing the number of baffles and narrowing the tubes usually makes for a warmer bag - up to a point. On the other hand, more baffles means more cost and weight. Complex mixed baffle arrangements sometimes just conceal the fact that the shell was made in two smaller parts.
If you stretch the inner bag sideways somehow you still want some insulation: you don't want the down squashed flat. To achieve this goal good sleeping bags have a 'differential cut'. Basically, this means the outer layer of fabric is larger than the inner layer - think concentric circles. This is a Good Thing, if not essential, and all manufacturers proudly proclaim they use it on some of their bags, as though they are special. In practice, if you have one of those vary narrow tapered bags you do need it, but if your bag has a reasonable amount of room in you don't really need the differential cut. Just make sure the bag is not stretched tightly over your knees.
Some bags don't have baffles: the outer layer of material is sewn straight through to the inner layer. A tube for the down results, but the region along the stitching is very thin, has negligable insulation, and will leak heat quickly. For this reason the sewn-through design is not found on anything but very cheap bags designed for warm conditions or for use as an inner sleeping bag (Antarctica and all that). They are not really suitable for bushwalking. But check before labelling a bag as 'sewn through': some of the very light bags may look as though they are sewn through, but in fact there is a very small wall there. Some cunning sewing has been used. But check carefully and suspect the worst.
It isn't all that often that you have a good hot shower before getting into your sleeping bag. In fact, sometimes you may even be just a little dirty, sweaty and smelly. Without some precautions, your bag is going to get dirty and sweaty and smelly too. On the other hand, washing a sleeping bag is not something you want to do very often. The conventional solution is to use a liner: a sort of light inner sleeping bag, and to wash it after every trip. You can get (poly-)cotton ones and silk ones. The cotton ones are OK but heavy; the silk ones are dearer but genuinely warmer and much lighter. And yes, they do last a long time (and feel good too).
Buy a very long one so you can pull it right up over your head - keeping the hood of your sleeping bag much cleaner and keeping your face much warmer in the snow. Sounds claustrophobic, but wait for a really cold night before you judge. It helps keep some of your warm breath inside the bag, making you warmer. The amusing bit is that you can usually see out of the liner over your face quite easily, but all others see is this anonymous body in a bag.
A less conventional solution is to take some very lightweight all-covering pyjamas. I made some silk pyjamas out of a couple of old silk liners and took them to the Pyrenees for two months in 2004. They worked very well, and allowed me a lot more freedom to wriggle around. I put a hood on the jacket and used it. This kept my head warmer of course, and protected the hood of the bag from the grease in my hair. I use silk pygamas all the time now instead of a silk liner.
Yes, damnit, pillows. Why not? You use one at home for comfort, so why not in the bush? In fact, most of us find it impossible to sleep comfortably without a pillow. But you don't have to cart a whole pillow around with you. Many walkers find that a small cotton bag can be stuffed with some dry clothing and used as fine pillow. Note: this is one of those few places where cotton (or poly-cotton) has it all over most synthetics for comfort. Some carry a small blow-up pillow, while others carry a small piece of foam to go on top of a clothing bag for real comfort. What ever lets you sleep comfortably and weighs next to nothing. But do remember to wash the 'pillow slip' at the end of the trip: your face will put a lot of grease into it after a hard days walking.
The stangest thing is that the gear market historically has ignored the need for a good lightweight bushwalking pillow. Mats, sleeping bags, liners: they are all there, but not good pillows. Oh, sure, there are car-camping pillows galore. The author has been developing an ultra-lightweight comfortable pillow, and details may be found in the ultra-lightweight section under the My Designs section. The whole thing weighs about 100 grams, and has passed the ultimate test: my wife loves hers.
An idea which has surfaced recently from a ouple of sources is an inflatable pillow. A company in America produces these for ambulances and airlines - they were losing too many expensive 'real' ones. But don't get too excited about the idea. most designs are like sleeping on a balloon: your head rolls everywhere. And most of them make an awful noise when you move. I tried one a couple of times, but only for about 15 minutes before my wife rebelled at being woken continuously.
The main problem with a good winter sleeping bag is that for most of the year you will be too hot in it. Many is the summer night we have slept on top of our old heavy sleeping bags. Alternately, if you have a summer weight bag you are going to be a just a little cold in mid-winter, especially in the snow or even in a very frosty valley. There's nothing quite like spending the whole night shivering. A secondary problem is the weight: winter bags are much heavier, and in summer you are carting all that weight around for nothing. The only solution we have found is to have two or more sleeping bags: one for winter and a very light one for summer.
If you can afford it, a mummy bag rated for -20C (however that might be measured) should keep you nicely warm under almost any Australian winter conditions. That translates to about 700-800 grams of good down. Actually, that weight is probably a bit of an overkill in all but really cold snow conditions if you use some of the Tricks outlined below. You can get bags with even more fill than that, but I think the extra is marketing overkill: the larger quantities of down just get squashed and are wasted. If you buy a good bag from a good bushwalking shop it should last for 20 or so years, provided you use a liner and keep the bag clean. Storage is important, and is discussed below. Think of it as an investment for 20 years: that way it doesn't work out so expensive.
Good very light Australian sleeping bags have been very hard to find, probably because Marketing wanted to promote the most expensive winter bags (with the biggest profit margins). The secondary problem with the lighter bags is that the shell (made of cheap heavy fabric) sometimes weighs 700-800 grams, but has only 150-250 grams of down. This is ridiculous. Of course, you can find cheap bags which are not very warm, but they aren't very light either. There are a couple of models which are recommended by some walkers: the Nitro and the Hotwire by Mont, and the Snowflake and Firefly by Macpac. The makers tend to call these "extenders", meaning you put them inside another bag in winter for extreme conditions, but they can be used by themselves in summer. Unfortunately the Mont ones seem to have been taken off the market in 2004. This is odd, because the comment I had from one gear shop was that they could not keep them in stock: they sold out very quickly. More recently (mid-2006) One Planet have produced their Cocoon series, using light fabrics and 300, 400 or 500 g of down. These look very good indeed.
There are whole lot of American summer bags available via the web, but I have not had any personal experience with them. Some of them look to be absolute straight jackets. The European survey of American bags mentioned at the start suggested that the American makers all massively over-rated their bags as well. That said, there are some top American brands out there - both www.backpackgeartest.org and www.backpackinglight.com are good places to search for the good brands.
Some very light bags turn out to be warmer than you might expect. There isn't much down in them: in fact the fabric cover may be the heaviest part, but there is plenty of space for the down to fluff up. With a good quality high-loft down they seem to be far more efficient than the heavier winter bags, weight for weight, for this reason. However, you do have to buy two bags for this luxury.
A big problem in winter is moisture inside your sleeping bag. It doesn't have to come from outside the bag: you sweat during the night and that can fill up your bag with dampness (see below). You can limit the amount of sweat by being cold, but this solution does not always appeal. A strange solution is to use a 'Vapour Barrier Liner' (VBL) inside your bag. In essence, this is little more than a plastic bag. Now, before you recoil in horror at the thought of this, consider two things. The first is that VBLs are used routinely in some places - like the Antarctic, or by the US military in the Arctic. You don't do that unless they work. The second is that you probably have no experience of what a VBL is like under conditions of extreme cold. In fact, if you are wearing a set of thermals and the VBl has a soft inner surface, it feels quite comfortable - as long as you don't get hot! But this is a very specialised area of extreme cold weather gear.
This is important. When you sleep you do put some sweat and dirt onto the sleeping bag liner, but you also put a whole lot of sweat into your sleeping bag. I believe you can lose up to a litre of water each night this way, although most of it will be in your breath. You bag will slowly get damp, and a damp bag loses its warmth, and if stored like that it gets mouldy and the soft downy feathers break down. End of bag, and not a good thing.
You should wash the liner and pillow slip when you get home each time. Never mind that it was just one night: the dirt and sweat are there. In addition, let the bag air for a day, although not in the sun. Too much sun and you will get UV damage to the fabric. We spread them out on a spare bed in a well-ventilated room for a few days after a trip. Then store the bag loosely, with the down all fluffed up. You can store it in a large light cotton bag for extra protection if you want, but it isn't essential. The top shelf of a wardrobe is just fine for storage. It will last a lot longer that way.
You will probably notice that there are a few feathers floating around in your tent in the morning. It is a sad fact of life that modern light-weight fabrics cannot prevent a few bits of down from escaping, often through the seam holes. It is unlikely that the few bits you lose will affect the warmth of the bag, but you can pull some bits back inside if they are only half way through. This is probably more cosmetic than effective, but it is satisfying.
The other hazard for down (apart from rough treatment and mould) is damp. Moisture makes the down stick together or clump, and away goes the air. Even if it didn't rain, you sweated each night in the bag and some of that will stay in the down. A bit of TLC* at home is a good thing, and is covered under maintenance. Note that wet down takes for ever to dry, and keeping your sleeping bag dry is worth fairly extreme efforts. It is also said that extended storage of wet down will accelerate it's breakdown.
If the trip is fairly long you may feel that your bag is losing it's warmth towards the end. This could be true, but is most likely due to the bag slowly getting damp from the moisture you generate each night. During a long trip it can be very worth while hanging your bag over the tent as soon as you pitch the tent, in the sun. Take it in as soon as the sun goes off it, or it will get damp very quickly. You might be surprised at the improvement in warmth each night. This can even work in the snow, as long as the sun is up. This (the sun in our snowfields) does happen sometimes.
Actually washing a sleeping bag is something to be avoided if possible. It tends to reduce the loft of the down by stripping out the proper duck oils (seriously). However, when the bag is so dirty that the loft is reduced anyhow (body grease), the time has arrived. Use a small amount of proper down soap or liquid obtained from a good bushwalking shop and follow the directions which come with it. Remember that the sleeping bag shell is not all that strong, and the baffles inside some designs are even weaker and can rip under the weight of a wet bag.
Two methods widely recommended are a front-loading washing machine on the most gentle cycle, and your bath. Top loading machines seem to agitate a bit too roughly. For the bath method (very safe) you lay the bag out in the soapy water and gently walk up and down on it until it is wet, then you massage it gently. Either way, make sure you give it a couple of good rinses to get all the soap out (and another rinse for good measure), and then scoop it up very, very carefully in one compact bundle. Do not try to separate the wet down: you won't succeed and will only damage it.
If you are going to spin dry the bag, be very careful how you arrange it in the tub. It must be packed very loosely around the rim, so no part of it gets stretched. This is very important. However, this will only strip out part of the water: you still have to dry the down inside.
There are also two methods for drying the bag - or rathe rather down inside. The first is a very gentle, warm, front-loading tumble drier, with a couple of tennis balls thrown in to massage the down. Some people have suggested using a pair of old Volleys instead of tennis balls: not with the smell of my Volleys thank you! The second is to let it dry in the wind with a little sun to warm it up, first on the ground and later (when apparently dry) on the clothes line, and to give it a bit of a gentle beating when nearly dry to stir the down up. Allow a whole sunny day for the drying process: it really can take that long to get the water out.
Some dry cleaners advertise that they can wash sleeping bags. They can, but the result is not as good as you might wish. They get the dirt out, but the solvents used tend to strip the proper duck oils off the down, which reduces its life. In general dry cleaning is to be totally avoided for good bags.
Once you have done all this, buy and use a liner inside the bag, and wash that regularly.
Remember the 3C rule: you aren't out there to suffer at night (you will do plenty of that on the hills in the daytime). Also remember that you are likely to be spending nearly twelve hours in your sleeping bag lying on the cold hard ground. The night can be awfully long if you are uncomfortable. Why not make sure you get a good night's sleep and are ready for the next day - with a comfortable mattress under your bag?
Incidentally, while everyone knows that lying directly on the snow is going to be cold, not so many realise that soft warm sand gets very hard and cold after a couple of hours at night. Try it yourself. Conversely, many people think that sleeping on the snow is going to be terribly cold and uncomfortable, but with the right gear we get a very comfortable night on the snow. This is explained below.
The generic term for these seems to be "Therm-a-Rest"®, but that is actually a registered brand name owned by Cascade Designs. There are quite a few other brands available, all looking fairly similar. The cheaper ones may just be a bit heavier, and don't seem to last as long. Some cheap brands have been reported to die within days. The construction consists of a slab of open cell foam with a layer of airtight fabric glued to the top and bottom surfaces and sealed around the edges, plus a small valve in one corner. Starting with a tightly rolled up mattress, you undo the valve and let the foam swell up, sucking air into the mattress. After about five minutes you can add a puff or two and do up the valve: the mattress is inflated and ready for use. This beats the hell out of the "blow up the Lilo" ritual which leaves your head spinning from hyperventilation. In addition and very importantly, the foam stops the air inside the mattress from moving around, just as down traps the air. So these air beds are very warm underneath, and they work very well on snow and ice too.
You can get these mattresses in full length and 3/4 length: the 3/4 length is usually quite enough. Put a bit of spare clothing at the end for your feet, and especially under your heels. Heels can put a lot of pressure on the ground and get quite cold. In the snow a bit of thin (3-4 mm) closed-cell foam may be desirable under your feet as well - and you can sit on the foam at lunch time. You can get these air mattresses in various thicknesses from 1.5 cm to over 5 cm: that's your choice. The author prefers the Deluxe LE (thickest) version, 5 cm thick. It is about the same weight as the thinner ones, but a whole lot more comfortable.
It is easy to blow one of these mats up too much. You may not do it any real harm, but the mattress will feel hard and uncomfortable. Your weight should be spread right across the mattress, so you don't need a high pressure to start. It only takes a couple of puffs to get the right pressure, which lets your hips almost reach the ground (but not quite!). Don't use any more. On the snow you will see a bit of a depression under your hips in the morning where the snow has melted, but you won't feel the cold. Actually, snow is quite comfortable to sleep on with a good mattress for that reason: the snow quickly melts to match your body shape, leaving a nice uniform thickness of foam between you and the snow. Sand on the other hand just gets harder and colder. If the mattress doesn't feel all that comfortable in the middle of the night, try letting a wee bit of air out. Seriously.
You should never store these mattress at home in their compressed state: it takes the life out of the foam. Open the valve and let the mattress swell up. Leave the valve wide open during storage: it will let any water vapour from your breath dry out (slowly) over time. I usually allow our mats to sit in the sun or vaguely near a fire for half a day after a trip (with the valve open) to warm the insides up just enough to help with the drying. And above all else, never cut on your mat or poke a hole in the fabric! The mattress will collapse, just like a balloon. Needless to say, hot things are sudden death as well. Repairs are possible for small holes - a bit of PU "goo" such as Seam Grip™ should work. Some vendors supply patch kits, but the patches may require heat or the small tube of glue may expire.
The foam in the self-inflating mattresses is "open cell", like a lattice. If the foam is "closed cell" then each little pocket of air is trapped and you cannot really compress the foam very much. Closed cell foam is sold in similar sizes in walking shops to act as a (thin) mattress, sometimes flat and sometimes in fancy zig-zag patterns. Obviously they are not as comfortable as a 50 mm thick air mattress, but they do keep you just as warm, and they are a whole lot cheaper and more robust. Even a pair of crampons has little effect on them. This makes foam mats popular with youth groups and mountaineers on Everest.
On very rough campsites there is always the risk that your groundsheet could be damaged. If it is a sewn-in one the repairs can be expensive. It makes sense to consider putting your foam mat on the ground under the groundsheet in these cases. I wouldn't do it with a Therm-a-Rest type of mat though.
Our only objection to these foam mats is that novices often carry them on the outside of their pack, and the scrub scrapes little bits off as they go. The result is a track littered with little bits of coloured foam. If you must carry such a mat on the outside of your pack, put it in a nylon bag to protect it and the bush, or be labelled a stupid novice.
Again, this is actually an old brand name, although it gets used today as a generic name. They are the same as the self-inflating mattresses but without the foam. They do not self-inflate: you have to sit there puffing for quite a while. You end up hyperventilated and with your head spinning, which isn't all that nice. Most of them are quite heavy, and because the air inside can circulate, they are quite cold on the snow. They are not recommended for walking, but are good for canyoning.
An Australian-made alternative to all the above is the Permaflate. This is like a Lilo but uses smaller replaceable tubes to hold the air. The advantages are that it is much lighter, the tubes are smaller and effectively warmer, and it can be customised if you wish. It can be found at www.permaflate.com with technical details. Customisation is possible.
Right at the start we pointed out that a sleeping bag will not make you warm: it will only limit the rate you lose heat. That heat comes from within you. But there are many tricks of the trade we can use to improve our comfort and warmth. Some were mentioned before, but never mind.
A collection of interesting technical references about sleeping bags. Your contributions will help
From Aushiker via BackpackGearTest: 'According to a recent Backpacker Magazine article the Europeans are in the process of developing a standardized system (EN13537) that uses a sensor-laden mannequin to determine cut, cold spots and ambient temperature. On average, most bags are scoring 10 F (6 C) worse than their manufacturer rating.' Some American brands stand out as the worst offenders.
From Alex Tweedly also via BackpackGearTest a URL to the European Standard Aushiker mentioned: Mammut. 'This is a fascinating read about the history of sleeping bag testing, including 5 pages on EN13537.'
This information may be out of date (2002) or incomplete: if vendors wish to update it they should contact me. I will be happy to listen. The weights listed are "downfill/finished", but without a stuff bag. Some bags have waterproof shells, which are of limited use in Australia and are not recommended, but in some cases the company will make ones with ordinary shells to order.
Note added in 2005: You should compare the Australian-made bags with the imported American bags. It is hard to avoid the conclusion that some Australian companies are now aiming at the cheap end of the market (intentionally or otherwise). This is very sad.
A very revealing figure which manufacturers do not list is the weight of the shell. Typical cheap nylon taffeta shells are in the 650 - 850 gram range: grossly heavy. These days a shell should not weigh more than 350 grams, and preferably not more than 300 grams. The down-proof fabric exists for this - it is just a little more expensive. My shells weigh 250 g and 330 g.
Australian company, formed from three older ones. This company will still finish (2006) bags to order, and will use 800 loft down to order. They are very cooperative.
Australian company, based in Queanbeyan, with a factory in Fiji. Data from 2002.
The first Australian company making gear here. Now (2005) almost out of the high-end manufacturing market.
© Roger Caffin 1/May/2002