Thursday, Jul 24, 2008 at 14:08
Further to Ken's answer...
I think we need to understand why condensation happens before we can attampt to deal with it.
Cold air can hold less water than hot air. (From memory ) Air at 30 degrees can hold about 35 grams of water (per cubic metre.). Air at 10 degrees can only hold about 6 grams of water.
For example - Air which is at 30 degrees and contains 20 grams of water is said to be at about 60% RELATIVE humidity. If this hot air is cooled, the relative humidity rises, even though the absolute (20 grams) amount of water in the air stays the same. This air will reach saturation point at 25 degrees where the relative humidity is 100%. Any further temperature drop will force the water to come out of the air. When this air reaches 10 degrees it will hold 6 grams of water, be at 100% relative humidity, and shed the other 29 grams of water.
When you are in a tent, a swag or a camper a few things happen. The air around you is heated by your body and your breath. Extra moisture is placed into the air with your breath. So what you have around you is warm air with plenty of moisture in it. When this warm touches cold surfaces (like tent poles or tent fabric) it is cooled and the moisture is forced out of it. This moisture clings to the cold surface and eventually starts dripping.
To prevent this happening you can do a two things.
1. Remove the moist air by ventilation
2. Prevent surfaces from becoming cold by insulating or heating them.
In my opinion, using a cotton sleeping bag will only absorb the dripping condensation. It will not prevent it.