In your literature on your crayons, you give the etch formula for using nitric acid. Do you have a recommended formula or advice for using T.A.P.E.M. with
your drawing materials?

I am assuming that you are using the T.A.P.E.M. etch formula on plates.
This etch works great!! On the majority of drawings a 50/50 etch will work
fine. That's half T.A.P.E.M. and half straight gum. On drawings that are
particularly dark you could use the T.A.P.E.M. straight. This is assuming
that the straight etch is at a pH of about 2.0-2.3