View Full Version : A little experiment I would like to try. (Enlarging for Cyanotypes)

5-Oct-2011, 16:21
So I just found this forum 2 hours ago, and I have all these ideas in my head that I haven't shared with anyone, so I just wanted to get a survey of reactions to this experiment I would like to try as well as any foreknowledge any of you may already have on the subject.

Essentially I remember one of my profs saying that enlarging a cyanotype (traditionally using a contact based printing method) was not possible. ('Not possible', not 'impossible', mind you) So that to me sounds like a challenge. This is the knowledge that I've gathered up so far but I haven't made anything yet since I'm still researching.

I know that there exists UV light bulbs that are used in scientific labs to sterilize cabinets. I also know that these lights will give you cataraks (as well as blindness) and skin cancer if you are exposed to them for too long, or even at all. A no-no for photographers especially.

There are also radiometers that you can use to monitor if your area is affected by the ligth bulbs so if the experiement continues I plan to buy one of those to be extra cautious.

So I'm thinking it would be possible to use a digital negative 4 x 5 to enlarge using an enlarger with this bulb. However given that I don't want cancer I wouldn't be anywhere near the darkroom when that light is off. I would use a remote timer and trigger far away from the source. This leads to: How do you focus if you can't use your eyes to focus it? (You can always just try and adjust repeatedly until you get it right I suppose.)

The next issue is if you are enlarging a digital negative, how will a 300dpi output look like enlarged. Is it going to show little dot grains? I think that is the most interesting part of the experiment.

Anyways I just wanted to get some reactions about this, good or bad, thoughts ideas.

I haven't decided if I wanted to do this yet,
Assuming I do everything correctly I am sure I can do this experiement safely but there always the unknown unknown.

I can hear my professor in my head saying, "Well if you're going to do a digital negative then why not just print it at the size you want?" Which is a good question, but I would be doing it for fun.
Finally if it doesn't pan out I would have to sell the lightbulb and the radiometer but that's not a big deal is it?

There feels nice to share something I've been mulling on, Now I can go think about something else haha :D

5-Oct-2011, 16:54
If you're going to make a digital negative, you might as well make it the right size for a contact print.

UV isn't radioactive, so it doesn't matter how far you are from a source. It just causes sunburns easier than most people realize, so as long as you avoid exposure, you're fine. I've gotten bad sunburns from the UV in welding before. Where clothes and mask covered the skin, I was fine.

5-Oct-2011, 21:07
I had a friend trying this and I think he was having problems because the glass in the lens was filtering the UV light out. Or something like that.

matthew klos
5-Oct-2011, 22:35
yea what is the point of this?

5-Oct-2011, 23:15
First, there are different types of UV light, usually divided by the wavelengths. The type used to sterilize equipment is UVC -- very dangerous and not the wavelength most useful in alternative printing. Absolutely no reason to use UVC emitting lamps.

Read this about UV light sources:


But it is appearently possible to make in-camera cyanotypes. Terry King of Great Britian (historian for the Royal Photographic Society) has developed a process called CyanotypeRex that has the sensitivity needed. He holds the info close -- I believe one has to buy a CD, so I do not have the info. But it is something along the lines of coating the paper with only the Ferric ammonium citrate, then after exposure, developing it in the potassium ferricyanide. Something along that lines. More info:



Steve Smith
6-Oct-2011, 00:20
I wouldn't be anywhere near the darkroom when that light is off. I would use a remote timer and trigger far away from the source

The company I worked at in the 1980's used UV light to expose etch resist for PCBs and emulsion for screen printing. We had a room with a 500 watt bare UV lamp hanging from the ceiling. There was no lamp holder, just two wires soldered to it with a plug at the other end.

The exposure method was:

1. Close your eyes.
2. Switch on lamp.
3. Get out of the room and close the door.

After the required exposure time the process was repeated in reverse. During exposure there was a bright glow around the door frame!

Don't do this at home!!!


6-Oct-2011, 04:25
it can be done
but if you can make the right size
"internegative" i don't see why you would want
to do this, other than to have fun doing it / say it can be done ...
seems like less trouble just making ink jet prints reversed
to contact print, or an enlarged negative using ortho film or ...
sticking the sensitized paper in a huge camera and leaving the shutter open ...

sounds like fun though -
welders goggles are cheap !

Robert Perrin
6-Oct-2011, 12:03
If I were going to enlarge onto cyanotype or similar material for an experiment, rather than high powered UV I'd use the sun as the light source as was done with the early enlargers. Basically just a light tight bottom holding the paper and fitted with a lens and negative carrier topped with a condenser lens open to the light. The design is not too unlike the Daylab enlargers. Although limited to small negatives and an 8x10 print a non-working Daylab should be very inexpensive and not too hard to modify as an initial experiment. For a little history of the sun-powered enlarger http://brightbytes.com/woodward.html