Cyanotype experiments

Well, using the sun tanning lamp I tried some experiments a few weeks ago. I have finally found time to scan the results.

The objective of the experiments was to determine the amount of time required to reach maximum black (or rather in the case of Cyanotypes, blue) when exposed under a sun tan lamp. The contraption shown in one of my previous posts has allowed me to place the lamp at a consistent distance from the paper, so the experiments should be repeatable.

The first strip was exposed for 1, 2, 3 and 4 minutes. It was produced by shading parts of the paper just like exposing a test strip. The first strip shows that 1 minute is not enough and 2 minutes is too much. So I exposed a second strip to determine where between 1 and 2 minutes the correct exposure lies. The second strip is exposed in 15 seconds starting at 60 seconds. This time it is a bit more difficult to tell where the correct exposure lies, but it looks like it is around 90 seconds.

So now I know that 90 seconds is the least amount of time that it will take to produce maximum black (blue!) using the sun tan lamp. Now it is a case of producing negatives of the appropriate density to produce the required cyanotype.....

Using a sun tan lamp as a UV source

Well after the last post, I twigged that I was thrashed around a bit and the best approach is going to be to take a more systematic approach to Cyanotype.

There seem three key steps in producing a good Cyanotype:

1. Coating the paper evenly;


2. Getting the amount of exposure on the print to produce dMax (maximum black, or in the case of a Cyanotype, maximum blue);


3. Using a negative of sufficient density to be able to produce the right tone in the highlights (without blocking up).

Well, I seem to have 1 under control. But 2 was causing a significant problem. The sun produces a very variable amount of UV, particularly at this time in the UK. I decided to try a small sun tan lamp as a UV source. I found a relatively inexpensive Philips sun tan lamp intended for facial tanning. I managed to find one locally for around £50. You can even buy them on Amazon!

Next trick was work out how to expose the print evenly. This was fairly straightforward to sort by suspending the lamp across the top of a plastic storage box. The print was in the bottom of the storage box under a sheet of thick glass.

Thus, the lamp is suspended about 25cms above the print. Next step is to work out how long the print needs to be exposed for.......