Experiment 47: Metal Polishing with Toothpaste

Recently, I cast a fancy flower-shaped dinner plate out of aluminum.  I had to redo the casting twice to get something I was satisfied with, but eventually I got a good replica of the glass plate I used as a pattern.  Fancy plates are usually shiny, though, and my plate still had the rough texture of the casting sand.  To fix this, I sanded it with 80 grit sandpaper for a while and then sanded with progressively finer grits until I reached 1500 grit.  Each finer grit sandpaper removes the scratches left by the previous one until the scratches are too small to see.  The plate still wasn't very shiny at 1500 grit, but I didn't have any polishing compound, so I looked online for an alternative.

Toothpaste is used for brushing teeth, and it works for this because it has extremely fine abrasives in it that polish your teeth.  I squirted a bit of toothpaste onto my plate and then used a cloth rag to rub it around.  I scrubbed until the toothpaste became grey with aluminum and then washed it off.  I repeated this process for about two hours.

Finally, at the end of the laborious process of sanding and polishing, I cleaned the plate off with a toothbrush and soap to remove the minty fresh smell.  After drying the plate, I was stunned to see that it was really and truly shiny!  I hadn't expected a lot from the toothpaste, but it did a dazzling job of shining up the cast plate.  I was quite pleased with the end result of the casting, sanding, and polishing.