Mountains Plus Outdoor Gear

Sleeping bags come in two types:  goose down sleeping bags and synthetic-fill sleeping bags. The difference is the material that is used for the fill. The fill is the most important part of the bag. It’s what keeps all the heat inside. The fill should do a good job of trapping air, providing you with insulation against the cold outside air.

Down Filled Bags

Down is the most efficient fill for mummy bags, because it’s very light and traps air better than synthetic bags. This warmth for weight efficiency makes it ideal for backpacking.

Down Filled Bags compress better than any other known synthetics and so packs down to a smaller size. When opened up, a down sleeping bags goes back to its open state very quickly and more completely. It has almost fluid like properties as it readily fills up the spaces of the sleeping bags.

Good quality down originates from both the U.S.A. and China. A debate has been made in the past whether white goose down are better than gray goose down, but the difference is probably minor.

Down sleeping bags are marked as 600-fill, 700-fill or 800-fill. This is called the fill power. It is the number of cubic inches that 1 oz. of down will occupy.

The higher the number of fill power results in less amount of down required to fill the same space which makes for a lighter sleeping bag. This is achieved 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 reportedly used his for more than 20 years.

But down as a fill is not perfect. You need to avoid getting it wet or it will stop keeping you warm. And on a rainy day, the mud on your boots will dry faster than damp down in your sleeping bag.

Down is eye-poppingly expensive and demands rather more care and maintenance. In some cases, infrequent as it is, an allergic reaction may occur.

Synthetic Fill Bags

Synthetic fills have been around for years. Current name brands include Polarguard, Thermolite Extra, and Hollofil I & II.

There are three forms of synthetics each characterized by the length of fiber. All the three forms can be lubricated with silicon or other liquids to make them feel more silky, more down-like.

Even though down is still the best fill for sleeping bags, synthetics are not far behind. Unlike down, they can keep you warm even when wet and drying them is very easy.

Since synthetics are a lot cheaper than down, some folks believe that they will eventually replace all down-filled products. I doubt that.

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