A worn abrasive is one of the quietest costs in a bodyshop. It still looks usable, so it stays on the block — but it's cutting slower, loading up faster, and often leaving a finish that needs another pass to put right. Here's how to tell when a sheet, strip or pad has done its work.
It's taking longer to cut than it did fresh
The clearest sign is time. A fresh abrasive bites straight away; a worn one skates. If you're leaning harder, going over the same area again and again, or a job that used to take one sheet now takes two, the grit has rounded off and it's working against you. Pushing harder to compensate also tends to gouge or dig, so you lose on finish quality as well as speed.
The surface is loading up
Loading — sometimes called clogging or pilling — is when sanded material builds up in the abrasive instead of clearing away. You'll see it as shiny lumps or a smooth, greasy-looking film across the sheet. Once an abrasive is loaded it stops cutting and starts burnishing, which can leave the surface looking smooth but not actually keyed for the next coat. Net abrasives like Mirka Abranet are designed so dust pulls through the mesh rather than sitting on the surface, which is a large part of why they hold their cut longer on filler and primer — but even a net abrasive loads eventually, especially on softer materials or fresh filler.
The scratch pattern has changed
A tired abrasive doesn't just cut slower — it cuts differently. Worn grit can leave a coarser, more random scratch than the grade should, or it can start polishing rather than keying. If a panel is coming up glossier than you expect for the grit you're using, or the scratch pattern under a guide coat looks patchy and inconsistent, the abrasive has stopped behaving like its stated grade.
Physical damage
Some of it is just visible wear:
- Net strips with torn mesh, frayed edges, or sections where the grit has come away
- Hand pads or rolls that have creased, split, or lost their backing flexibility — a Goldflex Soft pad that's gone stiff or torn won't follow a contour cleanly any more
- Hook-and-loop backing that no longer grips the pad, so the disc spins or lifts under the machine
Any of these means the abrasive can't do its job evenly, and an uneven cut is harder to fix later than the cost of a new sheet.
What's worth keeping on the shelf
The practical answer is to have enough of the abrasives you use most so nobody's tempted to stretch a worn one. Mirka Abranet strips (70 x 420mm, £49.99) cover machine and block sanding on filler and primer with the dust-extraction advantage; Mirka Goldflex Soft (£41.99) handles the flexible hand work — edges, returns, and contoured areas a block can't reach. For which grade to reach for at each stage, our abrasive grit guide covers the sequence.
If you're going through abrasives by the box, an ATC trade account gets you trade pricing and bulk quantities that aren't listed on the site.
