Tin manages to attach to the glass. It strongly adheres exclusively at roughened locations, however. Now lightly rinse the piece and immerse in slightly acidified palladous chloride. Palladium either replaces or immersion plates the tin. Dip the piece in just mixed parts A and B of electroless copper.
Palladium acts as a catalyst to the reaction.
Rinse the piece off when the reaction slows considerably, and you see copper only on the inside and outside rims of the quartz. Copper cyanide baths are typically used to flash other metals in preparation for some other purpose. For example, an aluminum form or mandrel might be zinc immersion-coated. It may be the goal to grow a quarter inch of copper on this mandrel. If the zincated mandrel were directly immersed in the typical acid-copper bath directly, the zincate would dissolve before the copper could grow over it, and since direct copper plating of aluminum is unsatisfactory, the part could be ruined.