Wow, I was recently looking at my ancient bottle of KPR and was wondering if it still works. Do you use the developer that was sold to work with it or have you found a substitute? I used it long ago to photoetch brass jewelry. I used one of thos little spray thingies with it. Then there was some nasty seeming developer stuff (some sort of chlorinated hydrocarbon) which I no longer have. Then there was a nice dye to put on after developing (dissolving off the unexposed resist) to be able to see the remaining resist to "proof read it". The system worked very well for me but it did take a bit of doing to learn how. Date: Sat, 14 Dec 2002 13:22:01 -0500 From: "Rick C." Subject: Re: [EE]: Photosensitive chemical. I have used a chemical called KPR (Kodak Photo Resist). I don't know if they make it anymore. I bought a quart of it about 30 years ago and have sensitized over a thousand boards with it and I still have half a bottle of it. Google shows about 50 hits on it. Apparently it is toxic, but so is everything. I'm getting ready to release a new web page this evening showing how to make excellent circuit boards. I have not seen any spray on resist that actually works. Rick -- Looking forward: Alan Shinn Experience the beginnings of microscopy. Make your own replica of one of Antony van Leeuwenhoek's microscopes. visit http://www.mindspring.com/~alshinn/ -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.