I was trying to print out a cyanotype using a halogen flood light 500W. I used a cardboard mask which I moved every 5 minutes to test for shading and this seemed to work OK until I washed the print and everything washed out. When I tried in the sun it worked fine so obviously the halogen did not emit any UV light. Am I using the wrong kind of halogen light and if so, what type do I need ? Or did I not wait long enough ? The sun is intermittant in the UK that I need some kind of UV source to fall back on.

SPG