Quote Originally Posted by stephen_gray98 View Post
.... 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....
DISCLAIMER: I am absolutely no cyanotype expert. I've done 6 so far. So take this with a grain of (Ferric) salt.

If you got an image prior to washing, then so far as I know you had some if not a lot of UV light.

What I found was that the first few cyanotypes I tried to wash also "washed down the drain" even though I did full sun exposure.

Some website, I forgot where - maybe here, suggested to me that pH of the wash was too high. So I started adding a few drop of muriatic acid (hydrochloric acid for brick masons) to the rinse and the problem was solved.

My understanding is that any acid which brings down the pH should work. I used what was here at the house.

I'm sure someone with more experience will chime in if I'm out to lunch.