removing scratches from "large" copper plates

[IntaglioPrintmaker]

I'm a printmaker working on 20 oz industrial grade copper plates. I've got a couple of 24"x48" plates. I'd like to remove some deep scratches and bring the plates to a mirror finish. All the printmaking tech books suggest using hand tools. If there's a way to sand/buff the scratches out using power tools I would love to know how. ~Thanks!~

[mpierich]

Originally Posted by IntaglioPrintmaker

I'm a printmaker working on 20 oz industrial grade copper plates. I've got a couple of 24"x48" plates. I'd like to remove some deep scratches and bring the plates to a mirror finish. All the printmaking tech books suggest using hand tools. If there's a way to sand/buff the scratches out using power tools I would love to know how. ~Thanks!~

It would certainly be a lot safer to use hand tools. After working with aluminum and stainless for a long time, copper would be a dream to work on, for me. Believe me, it won't be _that_ much work with hand tools...copper is very soft compared with other materials.

Remember that removing deep scratches will result in a depression to some degree or another, unless you thickness the whole plate to the depth of the scratch. If that's a problem for making prints you might be out of luck.

[IntaglioPrintmaker]

Thanks for your response! Uneven plate thickness wouldn’t be a problem. I may end up using hand tools. I’d also like to know how to get the job done using power tools. I found the following instructions for polishing smaller plates. While this method would work for smaller plates, anything larger than say 9”x12” would be a bit unwieldy. ~Thanks again~

1. Mount the plate to a block of wood using small nails. The wood block should have a smaller piece glued underneath it to act as a handle.
2. Remove big scratches with stitched sisal wheel and black emery compound (cutting action)
3. Move to stitched muslin wheel with brown (tripoli) compound (first cutting, then polishing action)
4. Move to stitched muslin wheel with white compound (first cutting, then polishing action)
5. Move to buffing board or non-stitched muslin wheel with red compound until you have a mirror finish
6. Wrap your polished plates in soft paper towels for transport / shipping (I use Scott Shop towels made by the Kimberly Clark Corporation)

[jrow]

IntaglioPrintmaker,

The polishing steps you listed look good. I'm not sure how thick the copper is 20oz doesn't mean anything to me. If you can lay it flat and have some way of holding it so it doesn't slid, I would suggest trying a 6" pneumatic DA sander. Try using some 400 grit sandpaper, which is the same grit as the Emory. If the 400 grit paper doesn't take the scratches out move back to 220 or 320 grit. In fact I might even try to using a 3/8" drill motor with a 4" sisal wheel mounted on it with some Emory compound first. Go easy, as the sisal wheel cuts real fast.

John