173: Tumbling Acrylic

Hello! Yes, we still exist. Last November there was a very subtle change to the posting frequency announcement on website front page, where “monthly” was crossed off and “occasionally” put in its place. And then we took a break that never seemed to quite end. Until today.

I can’t even tell you where my mind dredged up the thought “Hey, I wonder what would happen if we threw laser cut acrylic in the jewelry tumbler?,” but it seemed like an interesting and easy idea. Ideally, we’d get a nice rounded edges and an interesting finish, but I didn’t know for sure. Luckily, experiments are what we love here on 52 Lasers (whether they work spectacularly or not)!

Lortone tumbler on a bathroom counter
My trusty Lortone tumbler. It was a splurge, but good for my mental health! My previous cheapo tumbler was stressful. I would never know if it would work, if the stinky barrel would deposit a film on my sterling, or even how hard it would be to the darned cover on or off. I broke a few nails with that one; at one point I even took a rubber mallet to it. This one is a breeze.

Jewelry artists have been using tumblers for a very long time to do what they call “mass finishing” of their jewelry. It’s pretty much the same process as rock tumbling, except a bit more delicate. Different media (or the abrasives that you put in the tumbler with your pieces) do different tasks, from cleaning and descaling, to deburring and even hardening and polishing. I regularly use the tumbler to burnish my handmade sterling silver ear wires I use over at Isette.

The Testing Plan

  • 4 different types of acrylic
  • 2 different tumbling media
  • Samples pulled out three times during a 24 hour period.

Acrylic Samples

Here are my test acrylic pieces, mostly dug out of my “cool acrylic scrap” box, are (left to right): Transparent fluorescent yellow cast acrylic (with vector lines and light shading), white cast acrylic, black cast acrylic and brushed silver topped 2 ply micro surfaced plastic. I needed 6 of each to have enough to test…honestly I should have had 7 to have a “control” as well, but hey, didn’t think about that until later. The two oddballs at the bottom are transparent teal acrylic with a mirrored backing that were just hanging around on the bench, and I unscientifically threw them in the tumbler as well.

Tumbling Media

The tumbling media was what I had on hand: stainless steel shot, and green plastic “fine cut” pyramids. I was tempted to pick up some regular rock tumbling grit as well, but I thought we should limit our variables. The media I have are for two different purposes. The smooth stainless steel shot is a finishing media and is intended to shine metal. The pyramids have a very fine gritty feel, like fine sandpaper, and they are intended to smooth pieces, but not shine them.

Everything was tumbled with plain tap water, but out of habit I put a squirt of Dawn dish soap with the stainless steel shot. I started doing that when I was having trouble with my previous tumbler leaving a greyish film on my silver – it helped keep the muck suspended and off the ear wires. I didn’t do that with the plastic media, since I wasn’t sure if it would harm it. I should try a plastic run with soap in the future.

Length of Time

And time is the third variable. While I thought I’d take out samples at the same intervals for both, but it didn’t work out that way. I ended up taking out samples of the acrylic in the stainless steel shot at the 2 hour, 8 hour and 24 hours mark. With the green pyramids, I took out samples at the 1 hour, 4 hour and 24 hour mark.

The Results

Stainless Steel

Left to right: 2 hours, 8 hours, 24 hours.

The stainless steel shots results were minimal. Because acrylic is already smooth, there wasn’t a whole lot of need to “shine” it. I thought since the acrylic is softer than metal, we might still see something interesting. I checked on them after an hour tumbling and no difference. So I threw everything back in and pulled a sample at 2 hours. And again a 4, and then at hour 24. On the transparent and white acrylic, I saw no difference in the tumbled pieces, no matter how long they spent in it. I didn’t even take a photo, it was so unremarkable. The black acrylic (which are the counters to the Moai earrings in my shop) developed some fine crazing and dots, but it’s barely noticeable. You have the have the light hit it perfectly.

This photo has all 6 tumbled unicorns, laid out by length in the tumbler. Top row is the stainless steel shot unicorns, bottom is the green pyramid tumbled pieces.

Unicorns, in the early tumbles, ended up more shiny. They have a “brushed silver” top, so the shot smoothed that out, and cleaned away any residual cruft from the laser cutting. The most interesting thing to happen with this whole batch is that after 24 hours, the surface of the 2 ply acrylic unicorns was getting worn away.

Green Plastic Fine Cut Pyramids

Here’s where things started working more like I thought they would. I checked the batch in the Green pyramid media at the one hour tumbling mark, and there was enough of a difference that I pulled a sample out. I pulled another one at 4 hours and was pretty happy with the results. I then left them tumble another 20 hours after that, for science.

Translucent Florescent Yellow Acrylic

The transparent yellows were the insides of holes cut to hold a battery in the fluorescent layer of Project 143: LED Lit Layered Badge. There are some vector lines, and a incredibly very faint checkered halftone down near the protrusion. This is where a “before” sample would have been helpful! Left side is the one hour tumble; you can see a haze starting on the surface. They get progressively more matte finish. The slight halftone pattern is pretty much indistinguishable on the 4 hour piece (middle) and gone on the 24 hour piece (right). The vector lines can still clearly be seen, though.

On the right piece, the 24 hour tumble, you can see some “scratching” near the bottom where it looks less hazy. For some reason, at this length of tumble, the matte finish is surprisingly delicate. Those are fingernail marks. I really think the 4 hour mark is the sweet spot here.

White Acrylic Triangles

The white triangles were hard to photograph. Because the changes were subtle, I put dots on the pyramid tumbled pieces, so I would know what stage they were in. When you make something matte it really is just adding texture to add more highlights to things. Under normal light, white highlights on white are, well, white. This test looks a little unremarkable, but the edges are more rounded, there is texture and there is a more… man-made intentional feel when holding them in your hands, if that makes any sense. It feels like more time went into this piece. But tactile feelings are hard to capture in a photograph.

On the left is the 2 hour stainless tumbled triangle, on the right is the 1 hour pyramid tumble. You can see the edges are already softening, and the surface is getting texture.
Angled in the sun just right, you can see the texture is much finer and uniform on the 24 hour pyramid tumbled triangle (left) vs the 1 hour (right).

Black Acrylic Moai Heads

The black acrylic turned out really well with the green pyramid media, I think. The edges softened, a the surface got a lovely velvety matte. Once again, I think the 4 hour mark was the sweet spot; the 24 hour tumble was susceptible to scratching. One thing I didn’t foresee was the “grit” or debris from the tumbling media depositing on the inner edge of the small cut outs. I didn’t try too hard to remove it; perhaps a swipe with a damp Q-tip would do it. Or possibly if I added Dawn to the tumble, it might keep the particulate suspended in the water better.

Bright light reverals some more of the surface texture…This post was hard to photograph!
2 hour stainless tumble vs. 4 hour pyramid tumble
4 hour vs 24 hour pyramid tumble You can see the surface is more delicate on the 24 hour tumble. I’m also a little surprised the lip was still intact!
Lovely surface shot. From left to right we have 2 hour stainless steel tumble, 1 hour pyramid tumble, 4 hour pyramid tumble, and 24 hour pyramid tumble
Edge comparison

Brushed Silver 2 Ply Plastic Unicorns

Ghost unicorn
Untumbled unicorn vs 4 hour pyramid tumble

At 1 hour, there didn’t seem to be much change to the surface of the silver unicorn. At 4 hours, the tumbled unicorn was showing some scratches on the silver surface, but was still there. At 24 hours, the unicorn was a ghost. Which is fascinating in its own way, and would be a fun technique to explore in the same way “distressed” collage is fun. Overall I think the 2 ply, especially the metallic versions, are a bit too sensitive for this kind of tumbling.

Unscientific Bonus: Teal Mirror Acrylic

Wow, I loved this one. The stainless steel shot cleaned up the acrylic which helped clarity, and the green pyramids made it look like a lovely bit of sea glass. Both samples stayed in their respective tumbling media for 24 hours. If I were to put it in production, I would cut back the time on both; both of the mirrored backings were slightly damaged by the media. But not nearly to the extent of the 24 hour unicorns.
Fronts. Left: Stainless tumble, right: Pyramid tumble
Backs. Left: Stainless tumble, right: Pyramid tumble
Nice edge detail shot

If you made it this far, congratulations. Lots of interesting variables here, and a fun way to “finish” your laser cut work. There were also avenues I’d like to explore – questions that came up when I saw the results of this test. Like, what happens if you tumble one of the matte pieces with the stainless steel shot? Would there be less crazing if we tumbled without the pins (the pointiest of the mix) in the stainless? What would happen if we put soap in with the pyramids? For having gone so many months being less than inspired, I have a lot of ideas that will be fun to try out – perhaps in a follow up post someday.

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