Acrylic Mirror Sheet: Silver Sprayed on Acrylic Treated with Tannin in Water and Isopropanol

Philips' Ponjee and Verwijlen (US 4,639,382, 1987) made silver hold on acrylic by first dipping it in tannin dissolved in water mixed with an organic solvent; tannin in plain water gave no bond. This is their isopropanol solution: 50–85 % water, 15–50 % isopropanol by volume, 3.0–5.0 g tannin per litre, which gave full bonding in their cross-cut test. The sheet is then sensitised with weak stannous chloride and silvered by spraying the silver solution and the reducer together. The picture: our diagram.