The copper plate is the positive (+) contact for the chess pieces.



I had a difficult time thinking of the best way to get the checkerboard pattern on a single conductive surface. The plate could easily be divided into 64 uniform squares, but that would look terrible. I briefly considered using two separate conductive metals (copper & steel, or similar), and making a checkerboard pattern by alternating squares of them, but that would take too much time and effort. I finally decided that sandblasting, the same technique used to make the original glass chessboard (I think, although it may have been chemical etching), would be the best way to get the pattern down on a conductive metal surface.



Sandblasting a checkerboard pattern into the copper sheet will result in 32 squares with the original shiny copper gleam, and 32 frosty squares that were exposed to the abrasive. The hardest and most time consuming part about this step was not sandblasting, but setting up a stop.



A stop is what prevents the abrasive material from etching / frostifying unintended areas of the plate. There are many ways of setting up a stop. The technique I describe involves using a large format printer with a vinyl sticker medium. While this method is probably inaccessible / unfeasible for most of the people reading this, the entire process should not be too hard to replicate with common household tools and materials (printer, exacto knife, tape, and (at most) a trip to Kinkos).





(Like always, the pictures say a thousand words, and are much more descriptive then I could ever hope to be with written instructions)- Polish the nicer of the two faces of the copper sheet with some steel wool, so that it is shiny. Shiny things are fun.- Using Illustrator I made a checkerboard pattern file with the same dimensions as the original glass chessboard. The printer I used was able to cut the lines on the adhesive sticker medium, so, once printed, all I needed to do was peel off every other square from the pattern. If you do not have access to a printer with automatic cutting then you can use a regular printer to print out the pattern onto an adhesive medium, and trace the lines with an exacto knife. The vinyl sticker paper I used was a perfect material for this job because it can be peeled off without leaving behind any residue, but it is strong enough to stay attached to the copper while being sandblasted. Make sure to test your material before using it, otherwise you will either end up with adhesive residue left behind on the copper plate, or a fuzzy edged out of focus looking checkerboard pattern (The out of focus appearance will happen if the edges of the square stickers begin to peel up while being sandblasted).- I used a large sheet of transfer paper to get the vinyl sticker pattern squared perfectly with the copper plate. Transfer paper is just like very large masking tape. If transfer paper is unavailable, overlapped masking tape can be used instead. Overlap the tape so that it so it forms a large square which is a bit bigger than the checkerboard sticker. Place the nonadhesive side of the checkerboard sticker against the adhesive side of the transfer paper, so that both sheets are sticky side up (The pictures should make this process very clear). Remove the backing on the checkerboard sticker, and peel away every other square. Lay the checkerboard sticker / transfer paper combo on a hard flat surface, sticky side up (duh). Carefully lay the copper sheet directly over the checkerboard sticker, so that the sheet aligns with it perfectly, and press down firmly . When you are confident that sticker has completely adhered to the copper sheet, flip it over and peel away the transfer paper at a sharp angle. Make sure all the checkerboard pattern stickers remain completely stuck to the copper sheet. Sandblasting - By far the most fun part of this step. If all the preparation was done correctly, the process of sandblasting is hard to screw up, and provides very impressive visible results. Take the copper sheet and sandblasting apparatus outside to a smooth flat area that you do not mind getting covered in garnet. One of the good things about sandblasting (copper at least) is that it is hard to overdo it. Unless the stickers start to fall off, it is almost impossible to "overfrost" the copper. You will reach a certain level of "frostiness" and will not be able to go beyond it. It is possible to "underfrost" though, and once you take the stickers off it is hard to go back, so just be sure that every exposed part of the board is evenly blasted.From this point on you should probably handle the copper plate by the sides, as fingerprints have a tendency of turning into nasty black smudges.