Once in awhile, a dye lot comes in of a base color of Fiber Reactive dye powder (which we use to mix other colors) that is difficult to dissolve and may leave undissolved dark "freckles" on the fabric. Dharma Trading company rejects dye that doesn't pass our "solubility test", but colors can definitely vary, especially the "mixing" reds like Fuchsia and Light Red, and mixes with red in them. For solid color dyeing, especially more pastel colors, this can be particularly annoying. On the other hand, tie-dyers and painters might never notice. This is not a consistent problem, but is something everyone should know how to deal with, and can happen once in awhile no matter where you buy your dye.
Dharma recommends the following dye dissolving procedure:
Always add liquid to powder, not powder to liquid. Smash the powder with a sturdy spoon while adding the liquid very gradually. This is called "pasting" the dye. (We recommend this method even for non-problematic colors, by the way.) When it is a well-dissolved slurry, it can then be added to the dye bath or the rest of the water can be added if it is for tie dye. For hard to dissolve colors, use Urea water instead of plain water to paste up the dye. (dissolve some Urea in hot water, then let it cool to lukewarm) Also a couple of drops of Calsolene Oil can help (breaks surface tension). Except for Jet Black, #250, Fiber Reactive dye powders should always be dissolved in lukewarm water (like a baby bottle), not hot or cold. **If you are concerned about the "freckle" problem, we suggest further straining it after its dissolved and mixed with more water, through something like thin pieces of silk(5 or 8mm Habotai works well) or fine nylon stockings placed in a funnel or strainer. Experienced dyers will tell you it is worth this little bit of time to ensure a freckle free dye job!**
Dyebaths - with hard to dissolve colors, add the pre-dissolved dye to the bath, and mix well, BEFORE adding the salt. Salt reduces solubility, so if you do happen to have tiny particles of undissolved dye, they stand a better chance of going into solution without salt.