the tin process after a while breaks down - the grain refiner - and stannous turns into stannic - also current density decreases due to stannic tin and breakdown of additive - deposit is not as pure and sufficient time is required to plate sae thickness as originally. Atotech does have what they call a clarifier - it willpercipitate all the stannic out - run a carbon on the bath - and ur off to the races once more. need more info e-mail me at [log in to unmask]