There was the talcum powder.

Perhaps it would do.
Quickly she shook the box gently over the glass.

Then she blew it off carefully.
Clear, sharp, distinct, there were the imprints of fingers! But the paper.

Talcum powder would not bring them out on that.

It must be something black.
A lead pencil! Eagerly she seized it and with, a little silver pen-knife whittled off the wood.