Dear Jon,(posted 8428 days ago)I see one possibility. You can use a so called intensifier. The problem is that most of them are at least hazardous. I found a formula which looks not as dangerous. It is a silver intensifier. Solution A: citric acid 3 g Hydroquinone 3 g water 1000 ml Solution B: silver nitrate 5 g water 100 ml Short before usage mix up 100 ml of solution A with 10 ml of solution B. This mixture is not very stable. After intensifiing the negative it shall be washed for a short time. After that treat it for 2 min with a fresh acid fixer. After rinse well. Treatment time: as required. Regards Wolfgang