Scratch art foam boards are very thin sheets of styrofoam that can be used as inexpensive printing plates. You lightly draw an image (ballpoint pen works best), deboss the drawing (again ballpoint pens seem to be the best tool for this process), paint the board, flip over onto paper, rub the back, and lift to reveal the print. With care, the plates can be used over and over again.
Some tips for using this product:
1) I found that fluid acrylics worked best for printing. The debossed lines aren't super deep or detailed; ink tends to fill in your printing lines while craft acrylics dry too quickly. Heavy body acrylics work similarly to inks as it tends to squish into the lines you are trying to print.
2) It takes practice to know how much paint to apply to the plate: too little and you won't get much of a print...too much and the excess paint will blur your image. The amount of pressure you apply to the back of the plate also affects the final result. Be patient and just play. "Oopsy" prints can be cropped and used in other projects so don't be too hasty and ruthless with your "mistakes."
3) I really felt the prints showed up best as light colors on a dark background but this may be just a matter of personal preference.
4) If your lines are not printing clearly, try deepening your debossing. You don't want to poke through to the back of the board but you can get a surprisingly deep mark without piercing the styrofoam.
5) As with any monoprinting, reverse any lettering before printing.
6) Clean the plates immediately after printing; the paint seems to dry very quickly on the foam.
7) You can add additional coloring and details to the final prints; the material isn't fabulous for super-refined lines so I add that after the fact.
8) Since paint does dry fast on this stuff, I found that smaller plates were easier to handle. I cut larger sheets (9x12-inch) into the smaller pieces that I needed. This extends the value of the product.