Contributed by Wuvie
Instructions are based on a small, inexpensive tumbler. Directions can also be used for larger tumblers. Simply adjust the contents of the barrel based on your tumbler size and barrel content limit. Remember, I am not an expert, just obsessed with tumbling things.
You will need:
A rock tumbler, common play sand, water, vaseline or other lubricant, broken glass, cut glass, tile, broken plates, cups, etc. Patience
TIP: Overloading a rock tumbler can and likely will cause it's early demise. Do not fill your tumbler more than the required quantity, which is typically 2/3's full.
It is advised not to mix opposing materials, such as glass with rocks with tiles, as you may not achieve the results you seek on all the items. It is better to tumble glass alone, tiles alone, rocks alone, etc.
Fill the barrel with water so the level of water is just barely above your materials. Add three to four spoonfuls of common sand. Smooth a small amount of vaseline on the outside of the barrel, then put the lid on securely and let 'er rip. If you simply want to knock the edges from the glass for handling, you don't have to run the machine for days on end. In fact, several hours will do a good job. You can take the tumblers off at any time and check for smoothness. The longer you leave the tumblers running, the smoother and rounder the pieces will become. Alter the time according to what you would like the finished product to look like. Remember, this will likely be a noisy process. If you have a garage or a covered area outdoors, it would be best to run your tumbler(s) where they may run continuously for days without causing anyone a headache.
If you must stop the tumbling process after it has tumbled for a few days, rinse the items off and drain the water. Depending on what you choose to tumble, the mixing action can actually produce a gunk very similar to concrete, which is a pain in the butt to get clean. When tumbling broken pottery, dishes, dinnerware and other items, it is a good idea to check the tumbler after two days, sometimes rinsing and adding more sand if the mixture is too thick and producing the concrete-like gunk.
Keep in mind that some broken dishes may lose their patterns. Designs on dinnerware in gold will rub off, as will most hand painted items. The way I figure it, if the design is still on the pieces after four days of tumbling in sand, it should be able to handle being a part of a stepping stone, mosaic item, etc.
Another fun thing to do with rock tumblers is to make cubes. If you happen to have a tile saw, try cutting plates into evenly sized squares, then tumble them. They come out a fantastic cube shape with nice soft edges, perfect for mosaics.
Remember, glass will take on a frosty look if left in the tumbler too long. While I do like the frosted look, also known as "beach glass," others might prefer it clear yet safe to handle, which can be achieved by reducing the tumbling time.