Real sea glass takes decades of waves and sand to make. A rock tumbler does the same job in a few days. Glass is softer than agate and quartz, so it needs a gentler, shorter schedule than rocks, and a little extra care with sharp edges.
Safety first
- Wear gloves when you sort, load and unload raw glass. The edges are sharp until they are tumbled.
- Keep it away from kids until the edges are fully rounded.
- Use bottle or jar glass: clean it and remove labels. Skip glass with painted decals, mirrors and anything you don’t know the origin of.
- Collect responsibly: only take glass from places where you are allowed to.
Load the barrel
Break or sort the glass into pieces roughly the size you want to finish with. Tumbling rounds the edges but takes off less than you might expect. Fill the barrel two-thirds to three-quarters full, using plastic pellets or ceramic filler to cushion the glass and make up the load. Tumble glass on its own, never with rocks: the harder stones will chip it.
The schedule
- Coarse, 60/90 silicon carbide: about 2 tablespoons per pound of load. Check after the first day. Most batches need a few days for the edges to round off completely. Keep going until no sharp edges or points are left.
- Medium, 120/220 (optional): one to two days for a smoother, more even frost that looks like the best beach finds.
- Stop there for a sea glass look. Pre-polish and polish will slowly bring the glass back toward shiny, which is a different look entirely.
Glass breaks down much faster than stone, so check it often, and pull it as soon as it looks right. The frosted surface comes from the grinding, not from a polish step.
Tips for the best results
- Colors: green, brown and clear bottles are easy to find. Blue, cobalt and aqua glass are rarer and make prized pieces.
- Thick glass tumbles more evenly and is less likely to chip than thin glass.
- Rinse well between steps, just like with rocks.
- Dispose of slurry safely: never pour it down a drain. See what to do with used grit.
Finished sea glass is perfect for jewelry, mosaics and garden decor. Pick up 60/90 coarse grit and 120/220 medium grit to get started, and ask us if you’re not sure how much you need.