Textile Dyeing Specialist Question:

Acid dyes are also used for dyeing wool - again, they require very hot water, so your fabric must be able to withstand any resulting shrinkage, matting, or felting. For this reason, I do not recommend dyeing already-constructed wool garments, such as coats, sweaters, or dresses, unless they are really large, and/or you are completely willing to experiment with the results.