Name: A

Message: I have a silk blouse from Valentino in Italy. I asked them about the thread, but they say they lo the design team, so don't know.  Another said it was polyester, but I am unsure if she is certain. Do you have any clues about what major designers use for thread when deigning silk clohing? It is a nasty royal blue, and I wish for it to be navy. It has a ruffled placket and lots of visible thread. Does polyester accept any dye at all, or just stay exactly the same?

It is rare for any clothing to be sewn with cotton or silk thread, unless it is being specifically marketed for garment dyeing. If the manufacturers are not certain, than it is extremely likely that the blouse was sewn with polyester thread. See my FAQ page on "Dyeing thread in pre-sewn clothing".

When you dye the silk blouse, the polyester thread will remain the original color. This does not always look bad; oftentimes people assume that the contrasting color effect was part of the original design. However, it does look less formal, which might not go at all well with your ruffles. On the other hand, royal blue thread will not look too bad with a navy blue blouse. If you hate the blouse the way it is now, you may as well try dyeing it.

100% natural silk is one of the easiest of fibers to dye. You can dye it with cotton dyes, such as fiber-reactive, all-purpose, or direct dyes, or you can dye it with wool dyes, which are acid dyes. Silk is a versatile fiber which, unlike wool, tends to resist damage from the high-pH dye fixative used with cotton and rayon. The soda ash will tend to soften the silk a little bit, though, so if the blouse is supposed to have a stiff hand or a shiny finish, you should use acid dyes, instead, which are named for the fact that they are fixed with a mild acid such as vinegar. If you are willing to either dry clean the blouse later on, or hand wash it in cool water separately from other clothing, you can use all-purpose dye, such as Rit or Tintex. If having the dye remain dark even after washing is important to you, use a more washfast dye such as WashFast Acid Dye in Jet Black, or Lanaset Jet Black, to darken your blue to navy blue.

In theory it might be possible to dye polyester and silk at the same time, by mixing a direct dye such as "iDye" with a disperse dye such as "iDye Poly". Unfortunately, I cannot recommend this because high temperatures are needed to dye polyester (a full boil, 212°F or 100°C, is required to dye polyester), but you should dye silk only at 185°F (85°C) or below. The higher temperatures are likely to damage the silk.

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