I got some Glowforge-ready plywood from a seller on Etsy, a variety of woods, and was excited to use them for some projects I’d been planning during the time my arms were not functional (broke left arm, tore right rotator cuff in September).
I used a piece of hemlock ply for one project, an engraved sign for a friend, but when I pulled the pieces out, I could see 2 flecks of a dark orange glitter, kind of fused in the engraved areas. I was puzzled by this, as I have no orange glitter in the house, and have used no glitter in any projects for several months. I removed the glitter bits, and found the wood underneath uncharred. I re-engraved and re-cut that piece, ending up with one small piece of the orange glitter in an inconspicuous spot, so used it.
A few days later, I cut a couple of boxes with engraving/scoring for Christmas gifts, using walnut plywood from the same purchase, and again had a few specks of orange glitter. I was able to remove them from the boxes, and camouflaged the lighter spots with some brown ink. Still, I was puzzled by it.
Yesterday, I came across an article about glitter from the New York Times, published in 2018, and read: “Plywood manufacturers insert hidden layers of colored glitter in their products to prevent counterfeiting.” Who knew?
(Apparently, robermar36 had come across this also, writing in February of last year about commercially available plywoods: “And some use Bondo mixed with glitter”.)