light source for cyanotypes

[jonsjons]

i have been trying for a couple of months now to find a useable light source

for making cyanotypes...other than sunlight, that is. i have tried a plant

light, a black light, and various bulbs that claim to emulate natural

sunlight. none have worked. do i need to purchase a real uv bulb, and if so,

where can i find one? any specific companies/models to look for? thank you

for your help....i'm pretty much dead in the water on this one.

[cats lab]

Hi,

you should try UV tubes for circuit board making you'll find in any good electronic components shop.

I used that and worked nice.

I built a light box with foam on the back of the cover to press the presensitized board on the film, and worked also for the coated paper for cyanotypes.

You can buy tubes and ballasts or buy an already done uv box. It's up to you.

I used 4 tubes about 3 inches from the glass and spaced about 2 1/2 inches from each other.

The only draw back of my box is that I should have done a cover cut in half to be able to lift the paper without taking any chances to move it, but I already had done the box for my electronics stuff.

I'll redo another that I will be able to use for both photography and electronics.

I might be tempted to hack an enlarger with hi power uv leds one of those days, just to try to see if it can work.

 

Be careful with the uv lights it's no good for your eyes if you look at them directly.

 

Cheers,

Cedric

[mark f]

I use 8 24" BLB flourescent tubes (black light) about 6 inches above my contact frame. I think most people use these for their exposure boxes. I haven't done cyanotypes in a while, but I use them regularly for other UV processes. Typically, my exposures range from 6-12 minutes. I think cyanotypes were closer to 12 minute in my exposure box. Remember that the amount of light reaching the print falls off drastically with distance so the bulbs should be as close as possible while still maintaining even light.

[frank.schifano]

The light falloff follows the inverse square law. Double the distance and the light falloff allows only 1/4 of the intensity to reach the target.

 

Reference: http://www.geofflawrence.com/photography_tutorial_inverse_square_law.htm

[stephenwood]

Out of desperation I picked up one of those face tanning lamps. 4 tubes in a timer box. I just rigged a cardboard box to hold the lamp above my contact print frame and viola, a UV light box. If I was doing more than a few here and there, I might go bigger, but it serves a purpose.

[douglas_howk]

I created an exposure box using ceramic light fixtures and 7 Damar 20w BLBs. Staggered the 3 rows; and gives me good coverage for up to 7X17 negs.