As part of my informal apprenticeship in metal working—i.e., taking jewelry classes and testing the patience of my friends who repair jewelry and restore motorcycles—I have ended up with a huge stash of abrasives. I probably have most of the abrasives that are legal for a grown man to own.
Rubber abrasive blocks—sometimes called Garryflex blocks, which is a popular brand—are a low-tech option that I find myself using more often than most.
These are rubber blocks, much like big erasers, with abrasive particles embedded throughout. They come in a range of grits.
I use the blue 60 grit the most often. A grit of 60 might seem too rough for watch cases, but it gives a fantastic finish to stainless steel.
For flat surfaces, you can simply pull the piece along the block. Here’s an old Seiko case, for example, that has mirror-polished sides and a brushed top.
These blocks have a nice, consistent abrasive. With some patient brushing, you’ll get a smooth, silky result.
You can get a superior radial finish on a case back with the 60-grit blue block.
These Garryflex blocks are excellent for polishing bracelets and clasps, too, if you don’t have a satin polishing wheel handy.
Just draw the block along the bracelet in a linear, consistent motion. After doing one direction, reverse the bracelet and brush in the other direction.
One virtue of the rubber blocks is that they are slightly spongy. Unlike an emery file, the Garryflex blocks have a bit of “give” to them. This sponginess comes in handy for contoured parts, like the ridges on a clasp.
As another example, this Illinois case back has two finishes: a bright mirror-polish on the edge and a brushed radial finish on the curved back. It’s easy to brush the contoured edge with the rubber block, but it would be trickier with a file.
But the spongy “give” has a downside, too. If the piece has a mixed of brushed and mirror-polished surfaces, pushing too hard can cause the block to wrap around the edge, brushing the side.
These rubber blocks have one big downside: they shed and shed and shed, much like pencil erasers.
Cleanliness is its own virtue, of course, but for polishing, having small, scratchy rubber beads everywhere can cause unwanted scratches. For example, a bracelet clasp might have a brushed top but mirror polished sides, so the shavings will scuff the sides if you aren’t careful.
You can deal with the shavings by blowing them off with compressed air or rinsing them off with water. Garryflex blocks are suitable for wet sanding, so frequent rinses are a good way to keep it all clean.
Like all abrasives, these blocks should be stored in isolation, like a sealed bag, to avoid contamination. If the coarse-grit and fine-grit bags rub against each other, the fine-grit one is ruined.
Once you own a couple of these, you’ll want to brush every shiny thing in the house—they’re oddly satisfying to use.