Contents: Insulation | Temperature | Cleaning

Insulation:

• Down: Goose-down fills are very light, compressible, durable and breathable.
  There are also various quality leves for down. The area where the birds live, the season when the down is picked, the mixture of feathers and down all affect it's quality.
• Synthetic: Synthetic fills excel in damp, cold conditions (they don't lose their insulating properties when wet, and dry quickly). They are slightly heavier and less compressible than down.

Car camping bags even with synthetic insulation tend to be too big to fit into a backpack and too heavy for backpacking. Many are cotton or wool which are not recommended for backpacking bags. (Wool is good for clothing, however)

Temperature:
Prior to 2005 there was no standard for temperature ratings of sleeping bags. Most listed what is a lower limit not a comfort temperature.
Consequently many experts recommended a bag rated at least 10 or 15 degrees lower than the lowest nighttime temperature you will encounter. Plus there are many individual differences, Metabolism, Women generally feel colder than men, What you ate or drank, your state of exhaustion and type of sleeping pad can also affect you comfort level.

The 2005 European EN 13537 confort rating normalizes the temperatures at which a sleeping bag can be used.
EN13537 requires a full-size mannequin with heaters and temperature sensors dressed in one layer of long underwear and a hat placed in the bag inside a climate-controlled chamber.

• Upper Limit -- the temperature at which a standard man can sleep without excessive perspiration. It is established with the hood and zippers open and with the arms outside of the bag.
• Comfort -- the temperature at which a standard woman can expect to sleep comfortably in a relaxed position.
• Lower Limit -- the temperature at which a standard man can sleep for eight hours in a curled position without waking.
• Extreme -- the minimum temperature at which a standard woman can remain for six hours without risk of death from hypothermia (though frostbite is still possible).

As of the summer 2010 Marmot. REI, The North Face, and Mountain Hardware, were implementing the new ratings, but others are still lagging.

In "Issues Concerning the EN 13537 Sleeping Bag Standard " at OutdoorInsustry.org, Elizabeth McCullough, Ph.D., at Kansas State expresses some concern about the standard.

Liners: (also called travel sheets)
Typically made of cotton or polyester, liners add very little weight to your pack
and keep your bag clean and sweet-smelling.
Plus, they add about 5° F to 15° F to your bag's comfort rating.


My silk liner will add about 10° and weighs 6 oz.
My poly liner will add 10-15° and weighs 9 oz.
A 40° marmot down mummy is 1 lb 3 oz
A 30° marmot down mummy is 1 lb 7 oz
My Slumberjack Denali Adventure retangular down bag is a 45° bag and weighs 2 lb, 12 oz

A vapor barrier (coated nylon) liner may add even more warmth and keep you hydrated,
but can become clammy in warm weather.
In cold conditions it keeps body moisture from condensing inside your bag.

Synthetic bags can be washed the same way.

Spot cleaning the shell with a paste of laundry detergent, water and a toothbrush is advised before washing the whole thing. This is especially true around the hood and collar where hair and skin oils tend to accumulate. By holding the shell or liner fabric away from the insulation, you can wash and rinse the area without getting the inside wet.

You can keep the bag cleaner by applying a water repellent product to the surface. See: How to Wash a Sleeping Bag | eHow.com
and Caring for Your Sleeping Bag: Expert Advice from REI

Storage:
When you arrive home from a trip, first air out the bag inside-out for a couple days to make sure it's dry. Then store in a large cotton storage sack

Repair:
Rainy Pass Repair - (888) Rip-Stop - Partner with REI
# 4415 Stone Way North
# Seattle, WA 98103

Links:
Temperature Standards - Sleeping bag guide - Mammut
How to Choose a Sleeping Bag for Backpacking: Expert Advice from REI
Backpacker Magazine - Gear Finder: Sleeping Bags
Guide to Sleeping Bags - Trailspace.com
Appalachian Mountain Club's Equipped: Sleeping Bag Warmth Update: European Norm rating system becoming industry standard
How to choose a sleeping bag - The British Mountaineering Council 2011