I have a sparse straight 5mm mohair in natural that I wanted to dye. I used the acid dyes purchased from intercal, but since it is sparse and only the mohair took up color, I'll have a piggy that looks peachy rather than a solid pink. I know that the backing doesn't always take up color, but this time, it didn't take up any.
I've purchased hand dyed fabrics from others and the backing and mohair are the same color.
Is that because they used two different dyes?
I don't know if it's cause I did not lower the pH low enough. (I gradually added more vinegar as the process went on). Or I was just under boiling rather than shimmering?
Acid dyes only dye the mohair. To dye both mohair and backing the same color I use Rit dye. I use their color formula guide to help get the color I want. Becky (another TT) told us that she mixes the dyes in some hot water to make sure they are dissolved before adding them to the pot. I did this last time and the fabric dyed very evenly. This is not an issue if you are using the liquid. It also helps to make sure your fabric is good and wet before adding it.
There is a whole section in the library on dyeing. The library is a drop down menu right above this post on the left. It is a wealth of information.
Just an interesting tidbit - I forgot this about acid dyes, and recently dissolved just a bit of brown and purple together to dye some cotton eyelet trim. The cotton took up the purple, but not the brown!
Another thing to consider doing is dyeing a light-colored mohair that has a dark backing fabric so that you don't end up with a white backing (assuming the darker backing fabric is a more appropriate color for your finished product).
Will have to try the RIT liquid next...