Sleeping bags are graded according to the lowest still-air temperature at which a particular bag will provide comfortable sleeping. This, in turn, depends on the loft, or thickness, of the filling when it is fully expanded.
Down fillings have the highest loft per unit weight. They are more expensive than synthetics and hold body heat better, but they flatten out when they get wet. Most synthetic fillings are fairly efficient when damp but deteriorate over time.
The quality of a bag also depends on its design. A good design holds the filling in place so that it don’t clump, allows the filling to reach maximum loft, and avoids cold spots – areas with little or no filling. If you want the best in a down bag, ask for “slant box with baffles”; for synthetics, ask for “double-quilt sandwich. ”
Choose a bag suited to your needs; an overstuffed one can be as uncomfortable in warm weather as a thin one in cold. If you camp in various seasons, 1ook for a medium-weight bag with a cold-weather insert and an outer shell of waterproof nylon or breathable resin laminate. If low weight is important, consider down. Mummy bags are the warmest; barrel and rectangular bags are less confining.
To properly care for a sleeping bag, always sleep on a ground cover. After every trip, air your bag thoroughly. Store it loosely in a large laundry bag (not a stuff sack) or hang it on a wooden or plastic hanger. Clean the bag according to the manufacturer’s instructions. Always wash a synthetic bag.
On camping trips, carry a needle and thread, some nylon rip stop tape, and a few safety pins. Tape any rips promptly before filling is lost. Be sure the fabric around the rip is clean and dry; hand stitch around its edges. Make permanent repairs at home. Use the safety pins to replace a broken zipper pull or, in the case of a broken or jammed zipper, to close the bag.