Eeeek! TCA is an acid. It works by doing a controlled burn to your skin. Acids are confusing- which ones are strong? which ones aren't? It is not like glycolic or fruit acids, which you find in facial products at the grocery strore, which in general are gentle acids which don't penetrate far. TCA is different. Depending on the concentration and number of layers you do of TCA, you could burn through the full thickness of your skin (!!!), cause pigment changes, and scar.
I do a lot of peels, and there is no standard "safe" concentration or number of layers. Every patient is different, and you need a trained professional who has done many peels to know what is safe, particularly in darker skin types.
I am surprised at the TCA for tattoo removal. Tattoo pigment is generally placed deep in the skin- if your peel penetrated deep enough to remove the tattoo, I would expect it would always scar or depigment.
