chalk Archives - Botanical Colors

Mordant Monday: Chalk and Madder Experiment

I just finished teaching A Nerd’s Guide to Mordants online this past weekend where we discussed the idea of adding minerals to the dye bath to develop deeper color. This is a technique that we’ve used in the PNW as our water is not very highly mineralized. Now many of the water sources in the United States are from groundwater sources that contain minerals like calcium and magnesium, and sometimes iron, so it’s easy to get rich reds from madder extract with little effort. However in Seattle, the water source is from snowpack and not from groundwater, so it’s somewhat … Read more

You Asked, Kathy Answered: What IS Calcium Carbonate?

YOU ASKED: May I ask what you mean by calcium carbonate? I read in your description of “calcium carbonate” you compare it to chalk. This confuses me because chalk is caso4•(H2O) while calcium carbonate is caco3. KATHY ANSWERED: What we call “chalk” in the US is Calcium Carbonate – CaC03, a powdery white material. The formula that you reference is Calcium Sulfate and it may also be called “chalk” but in the US, we commonly refer to it as “gypsum”. Calcium carbonate is used to mark soccer fields, as a dietary calcium supplement, an ingredient in antacids, and building materials! … Read more