Sheepskin insoles: sizing up, and cutting to fit

You can always cut an insole smaller. You cannot make one bigger, which decides the whole sizing question.

Size up, never down

Buy the larger size when you are between two, and round a half size up rather than down. The reason is not comfort theory, it is geometry: trimming works, and adding material does not. An insole that arrives slightly long is fifteen minutes of work. One that arrives short is a spare.

How much room it takes

Thickness in this category runs from around four millimetres for thin felt to around fifteen for full shearling, with eight being the usual all rounder. A shearling insole lifts the foot roughly a centimetre when it is new and settles back to about half that once the wool has packed down over the first week or two.

That means a boot which fits perfectly today will feel tight on day one and roughly right by the end of the month. In a shoe with no room at all, a thin one is the only honest choice.

Trimming, in order

Pull the original insole out first, if it comes out. Lay it on the new one and trace it: it is a pattern that already fits the shoe, which beats measuring. Cut inside the line rather than on it, put it in, and try the shoe. Then cut again in small steps.

A sharp knife handles thick shearling better than scissors, which crush the pile at the edge. Scissors are fine on thin felt. A little fringe along the cut edge is normal and does not unravel further.

Cut the pair one at a time and keep them with the shoes they were cut for. A trimmed insole belongs to one pair from then on.

Washing and drying

Wool wants a cool wash, around thirty degrees, on a wool cycle, and then air drying flat away from a radiator. Heat is what mats wool, not water. Two pairs in rotation means one is always dry, which is most of what people are actually after.

Dry them out of the shoe, both faces open to the air. An insole left in a boot overnight dries on one side only, and the side against the sole stays damp until the morning it starts to smell. If the pile looks flat after a wash, work it with your fingers while it is still slightly damp and it comes back.

What a wool insole is, and is not

A thin sheepskin insole is a thermal liner. It puts a layer of wool between a cold sole and a foot, and wool holds its loft while damp, which is the whole trick. It is not a shaped footbed, and it does not change the shape of your shoe.

If you are looking for shaping rather than warmth, that is a different product entirely and this is not it. We would rather say so than sell you the wrong thing.