I’ve written before about some of the cool applications of silicone polymers we’re seeing in consumer products these days. Here’s another example. The good folks at Rockler Woodworking & Hardware just sent me a couple of their new (ish) Silicone Glue Brushes, a clever idea for the shop I imagine got started when some enterprising carpenter appropriated a silicone pastry, or basting-brush, from the kitchen for glue-up work.
Apart from the small paddle at the other end of the handle, this is very similar to the cooking tool, but cheaper (at $4 apiece) than most of the “food grade” brushes I’ve seen online. Also, the bristles are bit thicker and more widely spaced than those on my silicone basting brush, which only makes sense for a brush designed to work with thicker liquids.
Rockler’s glue brush is 7.5″ overall and weighs 3/4 oz. The soft black silicone head, which pops off the blue rigid polymer handle, is 1″ wide by 11/16″ thick, with 49 bristles in an hexagonal grid. Each bristle is 1/16″ in diameter, and the face of the brush is slanted, with the shortest bristles about 1/4″ and the longest about 1/2″.
I first tested mine against Titebond II Premium, which is a fairly typical polyvinyl acetate-based wood glue. You can clean it up wet, of course, like a regular brush, by running it under hot water, but the real value of silicone becomes evident when you just let the glue dry into a blob on the brush. Unlike a natural or synthetic fiber brush, the solidified mass of glue doesn’t stick in the silicone bristles: just flex them a bit, and the dried glue falls off and/or pulls out in a single clump. I didn’t get a chance to test this, but Rockler’s advertising copy claims even fully-cured polyurethane construction adhesive (like Liquid Nails) just “cracks and peels right off the bristles.”
If, like me, you use disposable foam brushes to save clean-up time, a silicone brush can be a more environmentally responsible, and in the long run, probably cheaper option. You can essentially use it like a disposable brush, except instead of throwing away the whole thing, you just throw away the blob of dried glue.
Curious about non-glue uses, I also experimented with using the brush to apply latex paint. As you can see, the bristles are really too thick to give even coverage, causing visible streaks. It’s worth noting, however, that the amount of streaking varies with the substrate (plexiglass streaks much worse than plywood) and with the thickness of the paint. On the right material, with properly thinned paint (and maybe thinner bristles) a good paintbrush could be made from this stuff, too.
My latex paint sample wasn’t completely dry as of this writing, but I will post an update about how well it cleans up as soon as it is. I also have an ongoing test with two-part epoxy and am planning another with cyanoacrylate, all results TBA. I’m determined to find something that will ruin this brush!
Latex paint does, in fact, clean up fairly easily when dry. It’s not as easy, however, with latex paint, as it is with PVA glue, to simply grab the dried blob and pull it out of the bristles. Latex paint tends to pull apart rather than come out as a single blob, so cleaning the inner parts of the inner bristles is a bit of a chore. If I were going to use this brush for latex paint, I’d prefer to clean it while the paint was still wet, using the conventional method.
Two-part epoxy cleaned up surprisingly well—faster, even, than latex paint. The hardened epoxy is more rigid, and sticks to itself better, and simply flakes off the bristles and falls or pulls out in clumps.
The brush finally met its match in “thin” cyanoacrylate super glue which, as you can see, does not want to come out. Trying to pick dried superglue from the bristles pretty much ruined the brush.