potassium hydrogen tartrate and sodium cholride reaction

[pinzart]

First, let me say that I am not a chemist. I'm an enamelist with a question about chemistry.

One of the difficulties in enameling, is removing unwanted enamel from metal after it's been fired on. There are a number of methods, most of them very harsh. I recently stumbled upon a fairly simple method, but I'm curious as to why it's working.

I mix equal parts Cream of Tartar (potassium hydrogen tartrate) and Table Salt (sodium chloride) and just enough water to make it into a paste. I apply the paste to the enamel and place it in my kiln at between 1450 and 1500 degrees F for between 2 to 4 minutes, until the paste mixture has completely carbonized. I then remove the piece from the kiln and drop it into cold water. At this point I can scrub off the carbon with a wire brush, and all the enamel comes off with it, leaving the metal clean and ready for re-enameling.

I have tried just using thermal shock ito remove enamel n the past. That is, heating the piece as I did in the description above and then dunking it in cold water, but without the paste. This produced only very limited success. There was always at least a thin layer of enamel left that would not come off no matter how many times I repeated the process.

So, what is it the cream of tartar and salt are doing?? What are they producing when mixed and heated that is eating off the enamel?

These are such benign cooking ingredients, it's just amazing me they can have such an effect.

Your help is appreciated!

Pam East
www.pinzart.com