Name: mary kelly
Message: My spinning guild has a project using recycled plastic bottle fibre. Can you dye it? I've tried Gaywool and Easy Peasy dyes, both unsuccessful.

From my page on "Dyeing Polyester with Disperse Dyes":
Polyester is, chemically, a fiber made of poly(ethylene terephthalate), and can be made from recycled plastic bottles. Plastics marked with the recycle logo containing a number 2 are HDPE (high density polyethylene), plastics marked with the recycle logo containing a number 4 are LDPE (low density polyethylene), and plastics marked with the recycle logo containing a number 1 are PETE (polyethylene terephthalate - e.g., Dacron, Fortrel, Mylar).

Polyester cannot be dyed with acid dyes such as Gaywool and Easy Peasy. Both of these dyes will dye only animal fibers, such as wool and silk, as well as nylon, but no other synthetic fibers. They will not dye cotton (or other cellulose fibers such as linen or rayon), and they will not dye polyester.

The only type of dye that will work for polyester fiber is called disperse dye. To immersion dye using disperse dye, you must boil your fiber in the dyebath with a noxious carrier chemical, for an hour, using a large cooking pot that will never again be used for food. See "Dyeing Polyester with Disperse Dyes".

A couple of sources for disperse dye in the UK are listed under "Europe" on my page of companies that sell dyeing supplies. Rainbow Silks sells disperse dye, for preparation of iron-ons, but I could not find the carrier chemical for immersion dyeing when I looked at their catalog. Kemtex should have it; call them, or ask for their instruction sheet, to determine what it is called so that you can buy it from them. I have seen the carrier chemical being sold under the names "Polysol Carrier" (at Batik Oetoro in Australia), "PRO Dye Carrier NSC" (at Pro Chemical & Dye in the US), or "Polydeveloper" (at Aljo Dyes in the US), but I don't know what Kemtex sells it as.