Washing down bags and jackets without ruining them

A down bag that has gone flat is usually dirty, not finished. Body oils, sweat salts and fine dust coat the down clusters, weigh them down and stop them springing back, so the loft you paid for quietly disappears over a few seasons. Washing removes that film and returns most of it. The wash itself is simple. The drying is long, and it is where most bags are ruined.

Why a flat bag is usually a dirty bag#

Down insulates by volume, not by mass. A cluster is a branching structure that holds still air between its filaments, and the measure of that ability is fill power, defined in the IDFB Testing Regulations as the volume in cubic inches occupied by 30 grams (about one ounce) of conditioned down under a light weight.

One cubic inch is 16.39 cubic centimetres, so 800 fill power is 800 x 16.39 = 13,110 cubic centimetres, about 13.1 litres, from 30 grams of down. A bag holding 500 grams of it holds 500 / 30 = 16.7 of those units, which if every cluster lofted freely would be 16.7 x 13.1 = 219 litres of trapped air. Shells and baffles constrain that in practice, but the scale explains the sensitivity: anything that stops clusters opening costs litres of air, and air is the insulation.

Oil films make neighbouring filaments stick, so clusters clump instead of expanding and sag toward the base of each chamber. The bag looks patchy held against a window, feels thin at the chest and sleeps colder than its label. Soiled down also takes up ambient moisture faster, which compounds the problem across consecutive nights.

Clean sleep clothing and a liner push the interval out. Neither removes the need: a bag never washed in ten years has lost loft that shaking will not recover.

What ordinary laundry detergent does to down#

Down is a protein, keratin, carrying a little natural oil that keeps the filaments flexible. Standard detergent is built to strip oil and to leave brighteners, softening agents and surfactant residue behind. On a cotton shirt that is harmless. On down it strips the oils, leaves a residue that glues filaments together, and, in biological formulations, applies protease enzymes to a protein fill.

Fabric softener is worse, because it works by coating fibres with a lubricating film, which is precisely what stops a cluster expanding.

A down-specific wash is a mild, low-foam, low-residue cleaner, so it is not an upsell: it is the difference between a bag that recovers its loft and one that comes out clean and sleeps worse than before. Dose it for a half load and rinse at least twice whatever the bottle says.

Machine, bathtub, or neither#

A front loader with no central agitator tumbles the item over itself, which is a gentle distributed load. A top loader built around an agitator post grips fabric and twists it against fixed plastic. Baffle walls inside a bag are typically 15 to 30 denier fabric or fine mesh, sewn along thousands of centimetres of seam, and they fail under that twisting long before the shell does.

Drum size is the other variable. A winter bag has to tumble, not rotate as a wet lump. If your drum is rated below about 7 kilograms, a large launderette machine will do a better job.

The bathtub method works for anything and is the only option if the machine available has an agitator. Run 15 to 20 centimetres of water at about 30 degrees C (86 degrees F), mix in a small dose of down wash, lay the bag in and press the air out, then soak it 30 to 60 minutes. Knead along the baffles with flat hands or bare feet, never wringing. Drain, press the water out with flat palms, refill and repeat two or three times until no suds appear, then press the bag flat and roll it from one end to squeeze out more.

The transfer is the dangerous moment. Down holds a great deal of water, and lifting a soaked bag by the hood or foot box puts the entire load on a few baffle seams. We have not seen a published figure for the saturated mass of a bag, but the handling rule needs no number: gather the whole bag into both arms, or slide it onto a towel and carry the towel.

The wash, step by step#

1. Repair first. Tape both faces of any existing tear. A 5 millimetre hole becomes a 20 centimetre split in one cycle, and then you are chasing wet down around a drum.
2. Prepare. Close every zip, fasten hook and loop tabs so they cannot abrade the shell, loosen all drawcords.
3. Pre-treat. Rub a little down wash into collar, hood edge and cuffs and leave it 15 minutes.
4. Set the machine. Delicates or wool programme, 30 degrees C (86 degrees F) unless the care label allows warmer.
5. Dose light. Down wash at a half load dose. Excess cleaner is residue, and residue is matting.
6. Add two extra rinses. Suds still visible in the drum window at the end means run another.
7. Spin gently. 400 to 600 rpm removes a lot of water and can cut an hour from the drying. If the label forbids spinning, follow the label.
8. Move it supported. Both arms or a towel, straight into the dryer.

Drying: the part everyone cuts short#

Use the lowest heat setting, and add three to six clean tennis balls or wool dryer balls. They strike wet clumps and break them apart continuously, which is the work you would otherwise do entirely by hand.

Plan on three to six hours for a bag and one to three hours for a jacket, run as 30 to 40 minute cycles rather than one long one. Between cycles, lay the item flat and work along every chamber with your fingers, pulling hard clumps apart. Early passes produce many. By the third or fourth there should be almost none.

Heat is the risk. Nylon does not melt until well over 200 degrees C, but shell coatings, repellent finishes and elastics degrade far below that, and a hot dryer can glaze a 20 denier shell permanently.

The finish test is tactile and not optional. Lay the item flat and pinch every chamber in turn between finger and thumb, working head to foot rather than sampling. Down that is still wet feels cool, dense and ropey inside an otherwise lofted chamber. One cool lump means another 30 minutes. When there are none, leave it hanging or laid out uncompressed for 24 hours, then store it uncompressed, as covered in storing gear between trips.

Air drying takes two to three days indoors with clump breaking every couple of hours, and down left wet that long in still humid air can pick up a mildew smell.

The loft check that tells you whether it worked#

1. Lay the bag on a hard flat floor, zipped, and shake it out along its length.
2. Leave it 30 minutes to settle. Down keeps lofting for longer than people expect.
3. Stand a ruler vertically beside it against a book or box and read the total height of the bag, bottom layer plus top layer, at chest, hip and knee.
4. Average the three figures.
5. Repeat 24 hours after drying, same floor, same 30 minute settle.

Heat flow through an insulating layer is inversely proportional to its thickness. If average total loft goes from 4.0 to 5.0 centimetres, thermal resistance rises by 5.0 / 4.0 = 1.25, so heat flow falls to 1 / 1.25 = 0.80 of what it was, a 20 percent reduction. Read the other way, a bag that has lost a fifth of its loft to dirt is passing about 25 percent more heat than it was designed to.

For a rough absolute figure, lofted down behaves as a material with an effective thermal conductivity near 0.035 watts per metre per kelvin, slightly worse than the 0.026 of still air because the filaments conduct and radiate. About half the total loft is above you, so 5 centimetres total is 0.025 metres over the top: 0.025 / 0.035 = 0.71 square metres kelvin per watt. That is a first order model, not a rating, and why one number cannot describe a night is set out in sleeping bag temperature ratings.

If loft does not improve, check three candidates in this order: it is not actually dry, cleaner residue is still in the fill and needs two more rinses, or the clusters have genuinely broken down with age. Only the third is terminal. It is also where the down against synthetic comparison matters, because synthetic fill loses loft through compression cycles rather than soiling, and no wash brings that back.

What goes wrong at each step, and how to recover#

Common mistakes#

Not washing at all. The belief that washing hurts down is the most damaging habit in down care. Years of body oil hurt it far more, and that damage eventually becomes permanent.

Dry cleaning. Standard solvents strip the natural oils. A few specialists run a down-appropriate process, most high street cleaners do not and cannot tell you which they use.

Hanging a wet bag on a line by the hood. The full weight of the wet fill lands on the top baffles. Dry it flat or in a dryer.

Stopping when the outside feels dry. The shell dries first and fast. The core of a clumped chamber can stay wet for hours after that.

Using a wash-in repellent on a down jacket. It coats the inner face too, which is rarely what you want on an insulated garment. The wash-in against spray-on choice is covered in reproofing rain gear, and fill trade-offs in insulated jackets.

Frequently asked questions#

How often should I wash a down sleeping bag?#

Roughly every 20 to 30 nights of use, and at the end of a season regardless, so body oils do not sit in the fill for months in storage. Clean sleep clothing and a liner stretch that interval. Visible loss of loft, a greasy feel at the collar, or a bag that sleeps colder than it used to are all reasons to wash sooner.

Can I wash a down jacket in a top loading machine?#

Only if it has no central agitator. The agitator post is the problem: it grips the shell and twists it against fixed plastic, and the lightweight internal baffle walls tear before the shell does. An agitator-free top loader is usable. If in doubt, use a bathtub, which is slower but carries no risk to the baffles.

What happens if I use normal laundry detergent on down?#

It strips the natural oils that keep filaments flexible and leaves surfactant residue that sticks neighbouring filaments together, so clusters cannot expand. The result is a clean bag with less loft than it had when dirty. Biological detergents add a third problem, since their enzymes are designed to break down protein and down is protein.

How long does a down sleeping bag take to dry?#

Three to six hours in a domestic dryer on low heat, run as 30 to 40 minute cycles with clump breaking in between, or two to three days air drying indoors. A large commercial dryer is quicker because the bag tumbles freely. There is no safe way to shorten this with higher heat, which glazes shell coatings and destroys water repellent finishes.

Will washing my down bag make it less warm?#

Done properly, the opposite. Removing oils and residue is how a bag regains loft, and loft is warmth. Washing damages a bag when the machine has an agitator, when ordinary detergent or softener is used, when a soaked bag is lifted by one end, or when it is stored before it is fully dry. Avoid those four and the wash is a clear gain.

My bag still smells after washing. What should I do?#

Confirm it is fully dry, because a faint musty smell is usually damp left in a chamber you missed. If it is dry and still smells, run a second wash with a down-specific cleaner and three rinses, since one cycle often fails to shift years of accumulated oil. A persistent sour smell after damp storage is mildew in the fill, and that is not always recoverable.