Cochineal, modifiers, and different types of wool

Cream of tartar is often used in dye recipes; particularly in the mordant process.  Various sources say that cream of tartar increases the amount of potassium alum sulphate that is absorbed in the mordant process, improves the hand of wool, and/or brightens red and yellow natural dyes.  In cochineal dyeing, it is important to use if the water contains minerals that make it hard; cream of tartar acts as a buffer and allows the cochineal to bond with the fiber instead of the minerals in the water.  As it is an acid, it will brighten reds and yellows.  It is not clear to me if if the hand of the wool is improved or if it helps with the mordant process.  It seems likely that if you are using hard water, it will act as a buffer and allow more of the potassium alum sulphate to bond with the fiber instead of minerals on the water; similar to the purpose with cochineal.

I usually use rain water when dyeing but decided to experiment a bit with different wools and a different mordant recipe.  For this batch, 20% potassium alum sulphate and 6% cream of tartar was used for the mordant.  The cream of tartar % was not enough to shift the cochineal to red so 10% tartaric acid was added in the dye bath.  The wools were a cormo, a Peruvian wool, and a cashmere wool blend.  The hand was nice on all of the yarns.  The cashmere wool blend (on top) is more orange red than the others but they all seem to have a similar value as far as the color.  No idea why the cashmere blend is a different color.

Acid can be bad for wool (causes it to felt more easily) so I neutralized part of one of the skeins in chalk to see the effect.  I have been told that citric acid, in particular, is bad for wool but am stilling wondering about that as citric acid is routinely used in the chemical dye world with acid dyes.   I don’t care for the effect of the chalk with cochineal (the chalk section is on the left of the skein at the bottom) so will continue to wash the skeins in a neutral soap rather than actually neutralizing the acid.

  

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