Washing and drying down and synthetic insulation

Insulation keeps you warm through trapped air. Down consists of fine, fluffy plumules without a hard quill, which loft into an airy cushion. Synthetic insulation imitates this with fine plastic fibres. This ability to puff up and fill space with still air is called loft. The more loft, the warmer at the same weight.

Sweat, skin oils and dirt make the down and fibres stick together. They then lie closer to each other, hold less air and insulate less well. A mild specialist detergent for down or technical textiles removes this dirt without stripping all the natural oils from the down. Ordinary detergent and fabric softener, on the other hand, can impair the down or the coating of the shell fabric.

Wet down clumps badly and takes a long time to dry. During drying the clumps must be broken up again and again, otherwise they stay stuck together and the loft does not return. Synthetic insulation dries faster and clumps less, but loses loft over time through frequent washing and compression.

Always start with the care label. It states temperature, spin speed, whether a dryer is allowed and which detergent is recommended. The instructions differ by product and shell fabric, so this entry deliberately gives no fixed temperatures or programmes. Close all zips and empty the pockets before washing.

Wash on a gentle cycle with a detergent for down or technical textiles and without fabric softener. A washing machine with an agitator in the middle of the drum, as found in some top-loaders, can damage seams and internal chambers; a machine without a central agitator or a large tub for hand washing is better. Rinse thoroughly, with an extra rinse if needed, so that no detergent remains in the filling.

Wet insulation is surprisingly heavy. Lift it out as a whole and support it with both arms instead of pulling it up by one corner. Otherwise the thin internal walls (baffles) that keep the filling in chambers can tear.

If the label allows a dryer, dry on low heat. Many people add clean tennis balls or special dryer balls; as the drum turns they knock against the filling and break up the clumps. High temperatures can damage the shell fabric and synthetic fibres. Take the item out now and then, shake it out and feel for clumps.

Without a dryer, spread the item flat in an airy, shady place. Shake it out regularly and tease clumps apart with your fingers. With down this can take many hours to days. Patience pays: half-dry down turns musty and can go mouldy.

The insulation is only finished when it feels evenly loose everywhere and no more clumps can be felt. Then store it loosely and airily, for example hanging up or in a large, breathable bag – not in the small compression sack.

The manufacturer's instructions and the care label always take precedence over general tips. The wrong detergent, too high a temperature or harsh spinning can permanently damage insulation and coatings. If the label says an item must not be washed, stick to that.

The most common mistakes are: ordinary detergent or fabric softener, a machine with a central agitator, high dryer heat and packing away too early. The last mistake in particular often only shows weeks later, when the sleeping bag smells musty or shows mildew spots.

A sleeping bag that has lost a lot of warmth through incorrect washing can become a problem on a cold trip. So after washing, test it first in mild conditions or at home before you rely on it.

Washing rarely but carefully is usually better than washing often. Every wash stresses fabric and filling. Clean small stains locally with a damp cloth and a little specialist detergent instead of washing the whole item straight away.

Prevention is easiest: a thin liner in the sleeping bag or a clean base layer for sleeping keeps sweat and skin oils away from the insulation. The liner is easy to wash often. Airing after every night also helps get moisture out of the filling.

For expensive sleeping bags some specialist businesses offer professional cleaning. That can be worthwhile if you are unsure or have no suitable machine. A well-cared-for item lasts longer and stays warm.