I make my own PCBs. I design them on Eagle cad, print them on transparent sheets (on a laserjet printer), expose the board to UV, develop the boards in Sodium Metasilicate then etch them in ferric chloride. I always use the same chemicals and same boards from the same supplier, I expose all the boards to UV for the same amount of time.
My problem is that I get inconsistent results.
About the only thing that I don't measure/control is the temperature of the chemicals, in the past I've figured this is ok because I can check the progress of these processes simply by visually inspecting the board every few seconds. (I do heat the chemicals, but only control it by feeling the sides of the tanks)
It's a bit hard to say exactly what's going wrong with some of the boards, but basically the board comes out looking 'dirty', I think that maybe the etch-resist is being attacked by the ferric chloride, but if i remove the board any earlier then the bits that do need etching are still joined together!
Advice and suggestions please?