This is the grinding station where I worked on my dad’s stained glass piece. Each piece has to be ground along the edges. These are fast powered circular grinders that work amazingly well to smooth the edges of the glass that you didn’t cut quite perfect.
Then you foil it. You have a copper foil tape that you line the edges of the glass with. The copper foil makes the solder cling to it when you are putting it all together. Foiling is pretty simple. You have to use the edge of a sharpie along the glass to make sure the foil is adhered perfectly.