Etching brass plates

Step 6 Check and finish the mask

This is the time to check that you're happy with the toner transfer. If you've messed up and need to start over, the acetone will dissolve the toner from the plate easily and you can try again (with a fresh sheet of OHP acetate though). If the toner layer is a bit thin, you can carefully align another printed sheet of acetate with your already partially-coated brass and try the toner transfer step again. This is one of the major benefits of using OHP film rather than the other options which people have said work (e.g. magazine paper, inkjet glossy paper, press 'n' peel toner transfer paper etc.). Make sure that the brass plate is free from bits of melted acetate, which can happen if you heat the acetate too much.
If you're happy with it, use the insulating tape to cover the back, sides, borders (if you want them) and any other large areas that you don't want to etch. Touch up any bits of the mask that look slightly thin on toner with the permanent OHP marker.