Mummy Bags And The Materials Used For Fillings – A Guide To Choosing From Down Mummy Bags And Synthetic Filled Mummy Bags.
Jan 29th, 2009 by DavePF
There are two types of mummy bags; goose down bags and synthetic filled bags. These are distinguised by the type of material that is used for the fill. The fill is the most vital part of the sleeping bag. It’s what keeps you warm on cold nights. A good fill is one that traps air well, providing you protection from the cold outside air.
Down-filled Sleeping Bags
Down is the most efficient fill for sleeping bags, warmth for weight, and traps air better than synthetic bags. This warmth for weight efficiency makes it ideal for backpacking.
Down-filled Sleeping Bags compress better than any available synthetics and so packs down to a smaller size. When opened up, a down-filled sleeping bags goes back to its open state more readily and quickly. It also acts almost fluid like as it readily fills up the spaces of the mummy bags.
Good quality down originates from China. The argument has been made in the past whether white goose down are better than gray goose down but there’s really not much difference.
Down filled sleeping bags are marked as 600-fill, 700-fill or 800-fill. This is referred to as the fill power. It is the number of cubic inches that 1 ounce of down occupies.
The bigger the number of fill power results in less amount of down required to fill the same space which makes the sleeping bag lighter. This is accomplished by using fluffier and longer-tendrilled down.
The American Society for Testing and Materials (ASTM) ordained standards for down content and fill power. By law, down must be at least 80 percent down i.e. cluster and fiber rather than quills, beaks, etc.
A good down sleeping bag will bounce back when you poke it with your finger. When properly taken care of, a down filled bag can last for a long time. One avid hiker I personally know used his for more than 20 years.
But down is far from perfect. When it gets wet it stops keeping you warm and it’s almost impossible to dry on the field.
Down is murderously expensive and requires more care in maintenance. In some cases, infrequent as it is, an allergic reaction may occur.
Synthetic Sleeping Bags
Synthetic fills have been around for years. They come in are distinguisedent name like Primaloft, Thermolite Micro, Hollofil I & II and more. The names change and the producers will probably come up with more names.
There are three forms of synthetics characterized by the length of fiber. The fibers can be lubricated with silicon or other liquids to make them feel more silky, more like down.
Even though down is still the best fill for sleeping bags, synthetics are not far behind. The advantage of synthetics is that, they still retain their insulating properties even when wet and drying them is very easy.
The biggest advantage, however is that they are a lot cheaper than down and there’s still room for improvement.
