Down And Synthetic Insulation After Ten Washes

Insulated jackets lose warmth over their lives, and most of that loss happens in the wash. The two common fills fail differently and require different handling.

Both fills work by trapping air

Insulation does not generate heat. It creates a thick layer of still air that slows the movement of heat away from the body.

Down does this with clusters of fine filaments that spring apart and fill a volume. Synthetic fill uses fine polyester fibers arranged to hold a similar structure.

In both cases the property that matters is loft, the thickness the fill occupies when uncompressed, and any loss of loft is a direct loss of warmth.

Down clumps when its natural oils are stripped

Down clusters carry a small amount of natural oil, and that oil helps the filaments stay separate and springy.

Ordinary detergent removes it, after which the clusters stick together into dense lumps that occupy far less volume than they did.

The garment then has thin patches and cold spots. Down-specific washes exist because they clean without stripping, and thorough drying with agitation is what breaks the clusters apart again.

Synthetic fill breaks down mechanically

Synthetic insulation does not depend on oils, so detergent choice matters far less and it can be washed more casually.

What damages it is repeated compression, which permanently bends and breaks the fine fibers so they no longer spring back.

The loss is gradual and irreversible. A synthetic jacket does not develop cold spots so much as become uniformly less warm, which makes the decline easy to miss.

Drying is where down is saved or ruined

Wet down is a compacted mass, and simply hanging it to dry leaves it that way permanently.

Tumbling on low heat with something to break up the clumps physically separates the clusters as they dry, restoring the loft.

The process takes far longer than the jacket's weight suggests, and stopping early leaves damp cores inside the baffles where mildew develops.

Storage between seasons matters for both

Compressing an insulated garment into a stuff sack for months damages down loft temporarily and synthetic loft permanently.

Hanging or loosely folding it in a closet preserves the structure at the cost of the space it occupies, which is the trade the fill requires.

Washing before storage is also worth doing, since body oils and soil left in the fill over a summer attract insects and degrade the fabric shell.