In this step it's important not to handle the parchment paper with your hands where the printing will happen. The oils on your skin will mess up the printing. Once it prints, handle it gently. It transfers really well, but the toner is somewhat delicate.
- Print your top layer pattern out on a regular sheet of paper reversed.
- Tape down enough parchment paper to cover the pattern with a one inch or better margin.
- Run the paper back through the printer.
- Print your bottom layer (not reversed) on another piece of parchment. You can re-use the first piece of plain paper and tape for the second parchment if you are gentle.
- pick out the right size of copper board and cut it to size. leave at least 1/4" margin from the circuits on one or more edges to have a solid place to tape.
- Trim the parchment paper fairly close to the traces, but leave a 1" or better margin along on edge to allow taping them together. When you cover the board, it should stick out on 3 sides and the paper should hang over the board on the fourth.
hint: The parchment will roll back up a little, if you flip the second parchment's curl the opposite way of the first it will be easier to align the paper later. In the pictures I combined layers and folder the paper (carefully) which also works well.
Confused? Sturmy explains it really well.
Ah, now I understand. So you print onto the paper to see where and how big the image will be. Then you tape parchment onto the paper so that the paper will be the right size, but the toner will be printed onto the parchment.
Then you print again, except this time the toner is on the parchment which you can detach from the paper and transfer the toner to the copper board.
offtherails2010 has some other hints (paraphrased).
1. You can use double stick tape under the parchment paper rather than Kapton [I tried this and it works great. You can even re-use the tape and paper easily. -Dustin]
2. If the toner doesn't stick well to your parchment or "Siliconized Baking Paper" you can spritz both sides with 99.9% Isopropanol to promote adhesion. Works on the copper as well.