The unique thing with metal clay is that most of your work will be done in the greenware stage. That is before firing. Working with metal clay in this stage takes practice to not waste a lot or you could end up with tons of paste or chunks to reclaim. First I will mention which sandpapers you can collect the metal clay from. Then I will discuss other methods of working your greenware with little to no clay being removed.
When you are sanding be sure you are conscious of what you can and can’t save. If you are using a brown grit sandpaper you can not save this metal clay. As little bits of the brown sand paper either physical or microscopic pieces will also be in your shavings. Turning this into paste or reclaiming into clay will make little pits in your piece where the sanding grit is mixed in. If you are sanding with wet/dry sand paper you can save these particles and reclaim. If you are using fabric/cloth sanders it is similar to the brown sanding paper and you can end up with little pieces of fabric filaments in your metal clay creations that will burn out and leave marks or lines in your metal clay.
If you have always sanded your piece to get you a nice finish you may think of healing your piece with smoothers and wet/dry sand paper. Moisture on your silver clay pieces in the greenware stage can be a blessing. Surface cracks and dips can be filled by using Healing foam, sponges and fine grit wet dry sand paper. Using a bit of moisture on say a 400 grit sand paper swipe it on your metal clay in one direction, pulling the clay to cover the groove. Only go in one direction. Let dry, repeat going another direction. Then use 400 cloth papers dry and lightly sand. If you still see markings you can repeat the process. If the marks are smaller go down to 600 grit sand paper and do the same thing. Going through this process with finer and finer sanding papers and cloths will get you close to a mirror finish before firing. When you feel you are close use the healing foams with a tiny bit of water or even a baby wipe and you will have a lovely finish.
What if you have a bunch of texture on your design you don’t want to lose. You can use the clay shapers with a bit of water on DRY green ware and smooth it in the groves to make that smooth. The top part of the texture can be done with the method above but you may start at 600 or 1200 grit so as to not file down the design.
Sometimes sanding our metal clay cant be helped but If you have big pieces to remove think of using a knife so that you can save these pieces for reclaiming. Using water with fine grit sanding paper and sponges can reduce waste and actually make your finishing quicker. Remember to not use too much water as it also makes your pieces softer. Intermittently work wet layer then dry on a coffee/candle warmer for best success. Have fun with your metal clay
Metal Clay enthusiast & Instructor