I'm looking at the potential to use residual laser toner as a replacement for colored embossing powder; they're pretty similar (given the caveat that toner is messy stuff to handle and clean up). I couldn't find anything in online searches.
Embossing powder is used in several ways. What might be the most practical for toner is melting it in a melting pot and pouring it into molds as a casting resin. But I don't know if toner is formulated to flow as a liquid when it melts.
The main way embossing powder is used is to add a 3D appearance to ink (i.e., embossing). That may be a challenge for toner. One big difference between the two is grain size.
Embossing powder has much larger grains. They're small and light enough to stick to the ink, but large enough to melt and flow together to form a raised plastic layer.
Laser toner has microscopic grains. They melt and stick to the paper, but a layer of toner particles is so thin that it doesn't form a raised layer. A big issue with toner would be getting a thick layer to stick to the ink.
People do color clear embossing powder by adding colored powders to it. So toner could theoretically be added to clear embossing powder. However, the tiny particles may interfere with the embossing powder sticking to the ink. Also, this doesn't seem like results would be consistent, and the toner color would be greatly diluted. This solution also requires expensive embossing powder in order to use the free toner.
Has anyone explored toner as a replacement for embossing powder (for either embossing or casting), and can provide insights on doing either one successfully?