Can you put silk pyjamas in the washing machine

Silk pyjamas in the washing machine: the honest answer is "sometimes yes, mostly no, and the difference is primarily momme weight." This is not a simple yes or no, but the variables are clear enough that the answer for your specific garment is usually determinable.

The relevant variable: momme weight

Momme weight is the weight of the silk fabric per unit of area. A 12-momme silk charmeuse is much finer and more fragile under mechanical stress than a 22-momme silk satin. The heavier the silk, the more structural resilience it has against the mechanical agitation of a washing machine drum.

As a general guide:

Below 12 momme: do not machine-wash. Fine charmeuse, chiffon, georgette, and voile silks at 6–12 momme have insufficient structural resilience for machine agitation. The filaments can break, the weave can distort, and the lustre can be permanently damaged by even a cold delicate cycle.

12–16 momme: can tolerate a machine wash in specific conditions (see below), but hand-washing is still strongly preferable. The fabric has sufficient weight to resist most of the mechanical damage, but marginal cases — a particularly aggressive machine, a hot cycle, a failure of the mesh bag — can still cause damage.

16+ momme: a cold delicate cycle in a mesh bag with a silk-appropriate detergent is generally acceptable for plain silk at this weight. Still not as good as hand-washing, but within the range where the risk of damage is low.

The required conditions for machine-washing silk

If you are washing silk in a machine, all of the following must be true:

1. The garment is plain woven or knit silk — no embroidery, appliqué, lace trim, or embellishment
2. The momme weight is 12 or above
3. The garment is placed in a fine mesh laundry bag, fully enclosed
4. The cycle is the coldest, shortest delicate cycle the machine offers — typically 20°C or 30°C cold delicate, not 40°C
5. The spin speed is 400 rpm or below — high spin tears fine fabrics and creates irreversible creasing in silk
6. The detergent is silk-appropriate, pH neutral — not standard laundry detergent

What breaks down under machine-washing even with good technique

Even with all conditions met, repeated machine-washing will degrade silk more quickly than hand-washing. The lustre diminishes faster; the drape changes more quickly; and the hand of the fabric — its soft, smooth quality — deteriorates. For a pyjama set used as sleepwear and washed frequently, hand-washing extends the garment life meaningfully.

For the hand-washing method, see how to hand wash silk lingerie without damage. The silk care guide is the full reference.