Yes, you can 100% make sea glass in a rock tumbler.
On the CAGW Facebook page a few weeks ago, I expressed my intention to try to make “sea glass” (ie. tumbled glass) in my kid’s rock tumbler, as soon as she finished the batch of rocks that she was currently polishing in there.
Many of you responded to this declaration with something along the lines of “OMG PLZ TELL ME IF IT WORKS OMG GASP OPEN-MOUNTED EMOJI OMG!!!1!!!!”
Based on these comments, I’m feeling like you want me to tell you how my experiment went.
Result: It. Was. AWESOME!!!
Yes, you can 100% make sea glass in a rock tumbler. It’s super easy, and it comes out straight-up looking like sea glass. Here’s how to do it.
How to Make Sea Glass in a Rock Tumbler
You will need:
rock tumbler. You want a good-quality metal one, something along the lines of the Thumler’s Tumbler that we own. Good rock tumblers are pricey, but they make a great gift for a science-minded kid, so much so that if you don’t have a science-minded kid of your own, someone you know probably has one and may in fact have a rock tumbler that you can borrow.
coarse grit. Unlike rock tumbling, which requires coarse grit, fine grit, pre-polish, and polish, making sea glass in a rock tumbler only calls for coarse grit.
broken glass. You don’t want anything too thin, like microscope slides, because the rock tumbler will abrade it so that it’s too thin to be useful. I had great luck with vintage glass bottles, however.
hammer and towel. Gotta break that glass somehow!
tile nippers. These aren’t necessary, but if you want to shape or trim your glass at all, you need them.
1. Break some glass. As I mentioned before, I’m using vintage glass bottles to make sea glass, because that’s what I have a million of and need to find more things to do with. I’m primarily choosing either the glass bottles that were broken when I found them, or that are of unimportant provenance. I clean up and polish the nice vintage glass bottles and display them around my house, even though I’ve frankly got too many of those, as well.
ANYWAY… my preferred method of breaking a glass bottle is to wrap it in a towel, set it on my driveway, then whack it with a hammer. From the mess of broken glass, I pick out the nice pieces that I want to tumble. I really like bottle necks and bottle bottoms (ahem…), and also the side pieces if they’ve broken into a shape that I think will look nice when tumbled.
Use the tile nippers to trim a piece of broken glass into a more interesting shape, or chip off the edges around a bottle’s bottom.
2. Set up the rock tumbler. Use these instructions to make your tumbled glass. Note, however, that the instructions explicitly tell you not to use glass bottles. My experience is that you can, although you still want to avoid any glass that’s too thin. A Coca-Cola bottle should work. A spaghetti sauce jar probably won’t.
3. Check your work. When you open up your rock tumbler after five or so days, the inside will look like this:
Instead of sifting out the tumbled glass, I pick it out of the matrix and examine it. A couple of times, a piece has cracked and needs to be set aside. Sometimes, a piece is perfect just the way that it is and I love it. Most times, though, the tumbled piece is almost perfect, but still needs some refining. For that, get the tile nippers back out.
For instance, after examining that bottle neck in the above photograph, I decided that I’d like it better if it was trimmed even closer to the edge, so I did:
4. Go for round #2. Pop any glass that you’ve trimmed, and enough new pieces to maintain the level in your tumbler, back into the barrel with the same grit and filler material. Give it a go for another five or so days, and then take a look. Repeat until you’re happy!
You can use your DIY sea glass for any projects that call for the real deal.