Cyanotype problems

[stephen_gray98]

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

[michaelbsc]

.... 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.
MB

[Barry S]

I've had good success using 26w (actual) daylight spiral compact fluorescent bulbs. Cheap CFLs leak a lot of UV. I use a grid of 16 in a Photodiox unit, but you can easily wire yourself a grid by mounting some edison sockets to a plywood board.

[Matthew Rusbarsky]

Try some vinegar to lower the PH of your wash, but I bet the issue is your light source. Google the wavelengths of halogen. Very little of it is in the UV range. When there is no sun, I use a single 15w BLB. Covers up to 8x8 inches and gives me exposures of about 1 hour with double-coated traditional chemistry. Also, overcast days are the best for printing cyanos outdoors. You might have more sun than you think you do.

[jp498]

The light you want that sort of sounds like a halogen light is a metal halide light. These are the coolish output lights used in gyms and on some street lights, they take a couple minutes to warm up. I got one for free. But if I had to pay, I'd build something with fluorescent UV bulbs.

[paul_c5x4]

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.

The Philips facial solarium (HB175) is quite popular amongst the Alt crowd in the UK - You should be able to find one on ebay for ten to twenty quid including postage. I scored mine for a measly £5.50 plus £8.00 P&P.

[Dan Dozer]

While I'm not an expert in Cyanotype, I have done a number of them. In addition to the light source, the paper could have some impact on how much "washes down the drain". I found that a thicker harder paper (like Bergger COT 320) doesn't let the cyanotype coating soak in as much and the emulsion seems to sit on the surface of the paper more than a softer paper. Bergger COT 320 works fine, but I found I had to increase my exposures signfiicantly.

[michaelbsc]

Try some vinegar to lower the PH of your wash, but I bet the issue is your light source. Google the wavelengths of halogen. Very little of it is in the UV range. When there is no sun, I use a single 15w BLB. Covers up to 8x8 inches and gives me exposures of about 1 hour with double-coated traditional chemistry. Also, overcast days are the best for printing cyanos outdoors. You might have more sun than you think you do.

Yes, vinegar was a suggestion I found, too. But for me the muriatic acid was handier than going across the road to raid the kitchen pantry. So far as I know any acid would have worked. At least any acid would reduce the pH, and I don't know that there are any acids which would interfere with the reactions in small quantities.

For paper I was using the presensitized paper from Freestyle. It worked fine once I got the pH down. But I can see that in the long haul I will want to coat my own.

[sly]

My well water is quite alkaline, so it's vinegar for me. My light's a tanning light, quite cheap from someone who wanted rid of it. I found paper can make quite a difference. Stonehenge is my favorite so far for cyanotype, though I don't like it for other alt processes. Another possibility is that you're just not exposing long enough.

No one's mentioned the glass. You don't want the expensive kind that blocks UV light.

[stephen_gray98]

Thanks for all the info. I'll look into a tanning unit first as I also want to get into gum bichromate. I did expose under an overcast sky but the exposure time is hard to guage.

SPG