Acrylic Mirror Sheet: Silver Sprayed on Tannin-Treated Acrylic

Silver from a chemical bath barely sticks to acrylic: tannin in plain water gave no bond at all. Philips' Ponjee and Verwijlen (US 4,639,382, 1987) found that tannin dissolved in water mixed with an organic solvent such as ethanol makes the silver hold firmly, without etching or clouding the acrylic. The sheet is dipped for a minute, sensitised with a weak stannous chloride spray, then silvered by spraying the silver solution and the reducer together. In the patent's cross-cut test, no squares of silver came off. The picture: our diagram.