After completing an entire kitchen remodel, I had acquired a shoebox full of sanding sponges with different grits, but now I don’t know which block has which grit.
I’d like to say I keep the original packaging for items like this, which would indicate the grit and other details for my sanding sponges, but that just doesn’t happen.
I learned my lesson! Now, before I toss the packaging in the garbage can, I write the grit number on the side of the sanding block with a permanent marker. I also do this with paintbrushes to indicate if it’s for oil, latex or all paints. — Matt Owczarczak
And remember, you can reuse sanding sponges that have lost their grit by simply wrapping them with sandpaper. The flexibility of sponges works great for sanding odd-shape items.