Is Glass Suitable for Tumbling?
Just about any manufactured or natural glass, may be successfully tumbled to a high gloss in a rotary or vibratory tumbler. It has an advantage over most tumbling rough in that it already has many smooth surfaces which once took a fine shine. It just needs a little refining to get it back to where it once was, minus the sharp edges.
Tumbled Glass is Not Sea Glass
If you have frosted Beach Glass, be advised that it may be quite valuable in it’s frosted condition. I keep all my beach glass separated from the glass I want to tumble. You never know when someone will want to buy the Beach Glass...
What Kind of Glass Should I Tumble?
Starting with beer bottles, wine bottles, old electrical insulators and other glass, I smash it to size I want, making sure not to cut myself, then put it in my tumbler for tumbling. See below for the grit sequence for the two types of tumblers:
Rotary Tumblers Vibratory Tumblers
Stage 1 80-Grit 220-Grit
Stage 2 220-Grit 600-Grit
Stage 3 600 Grit 1000-Grit
Stage 4 1000-Grit Polish Stage
Stage 5 Polish Stage
Making effective slurries is a major key to your success in tumbling. Please read the two articles, "Making Perfect Slurries" and "Obsidian and Apache Tears" under the heading "TechTips" at the top of this page. This important information is also available in the book, Modern Rock Tumbling, by Steve Hart.
In loading your tumbler, you should have between 33 and 50% of Ceramic Shapes to carry your slurry to all the “nooks and crannies” and to cushion the glass to prevent cracking and spalling (chipping).
Inspect your rotary-processed glass after two days in Stage 1 (if a Vibratory process, after just 4 hours). The procedure is to remove a few pieces from the slurry, rinse them off outside (over a paint bucket—see Caution note below) and take them inside to dry--check to see if the sharp edges have disappeared. If the edges are still too sharp, continue Stage 1 (called the “shaping” stage) for 2 more days or 4 more hours if vibratory, as above, depending on the type of tumbler you have. There is no need to wash up until Stage 1 has been completed successfully. When the edges are smooth enough, wash up and reload your tumbler, making up for lost volume with more ceramic shapes. Now proceed to Stage 2 for about half the Stage 1 time. Because glass is so soft, you want to keep checking at these short intervals so you don't sand away too much of the glass.
In the grit stages after Stage 1, you are checking to see that the scratch marks left by the previous stage have been removed. Thus, when you inspect a few pieces of your Stage 2 rotary-processed glass after 1 day (or 2 hours if vibratory), check to see if the 80-Grit scratches have all been turned into 220-Grit scratches (or if using Vibratory--when the 220-Grit scratches have all been turned into 600-Grit scratches). When they have, it's time to wash up and proceed to Stage 3. Keep proceeding through this tumble-and-check process until you reach the polish stage. Keeping good records during this process will save much time with subsequent batches!
The Polish Stage for Glass
Do a real good cleanup prior to polish. Your goal is to make sure not a single piece of Silicon Carbide grit goes into the polish stage. Load your tumbler carefully and proceed to make a perfect slurry—I strongly advise that you use Cerium Oxide polish, as It brings out a dynamite polish in all types of glass.
Start your tumbler rolling and let it run for a full week in Cerium Oxide Rock Polish (if Vibratory, for a full 12 hours). At the end of this time, pick out two pieces of glass and wash them over the paint bucket. Then take them inside and dry thoroughly with a towel. Both pieces should be shining brightly, with zero sharp edges. To make sure they are shining as brightly as possible, you need to perform the Polish Stick test. Moisten the leather on a Polish Stick and sprinkle Cerium Oxide on it. Now take one of the glass pieces and rub one area vigorously on the Polish Stick—rub for about a minute. Now look at the polish on that area and compare it to the other piece of glass. If the area which was rubbed on the stick has a better polish, that means that the whole batch needs another week (or 12 hours). When the polish on the dry rubbed area is no better than the polish on the dry un-rubbed glass, that means that the polish cannot be improved, and that further tumbling would not improve the polish. You have completed the polish stage successfully. Congratulations!
Now it’s time to wash up the whole batch and start displaying your tumbled glass for all to see.
The above procedures are recommended when you desire a high gloss product to display. Many individuals want to duplicate the natural weathering process and end up with grainy, frosted glass. If that is you, try this—run your glass for 2-3 days in 80-grit (or coarser), (4-6 hours in a vibratory tumbler with 220-grit) then go straight to polish (or) skip the Polish Stage altogether. Play with these procedures until you get the look you desire.
Caution: In my book, I explain how the tumbling dust can often be very harmful to your lungs, so it is important that you get the aqueous slurry captured in a paint bucket for later safe disposal. When the water evaporates from the bucket, you can remove the dried “slurry-cake” and dispose of it safely in a garbage bag. When tumbling glass and leaded glass, there is a lot of fine Silica and Lead in the slurry-cake, both of which can make you very sick after prolonged breathing of the dust.
We at Little Red Store are always happy to answer any tumbling or lapidary questions you may have. Just E-Mail or call us and we will be happy to help, whether you are a Customer of ours or not.
Good luck with your glass-polishing efforts!