There is quite a lot of information available on the web regarding the chemistry of the Kallitype and Cyanotype processes. At their core they rely on the photo-sensitivity of Iron (III) complex, either iron (III) oxalate hexahydrate or ammonium iron (III) oxalate.

This chemistry is orders of magnitude less sensitive than the common silver black and white photography chemistry that requires a dark room. Iron methods simply need to mitigate the UV, a closed blind with daylight or a medium tungsten bulb illumination suffice.

The exposure duration is calculated using the quantum yield of the iron (III) complex, this being the number of interacted molecules per photon of light. And the various absorption process, known as the molar attenuation coefficient. For Kallitype this is for the ammonium iron (III) oxalate, for Cyanotype it is the ferricyanide product, which produces a masking effect that effectively doubles the exposure time compared to Kallitype process.

The iron process is most sensitive to wavelengths of roughly 300nm, unfortunately laser diodes of reasonable power are not available at prices that feasible for this project. The most powerful reasonable laser diodes generally available are 405nm wavelength bluray diodes. These are available up to 900mW, which in this instance i'm looking at running at 450mW with TEC peltier unit to control the temperature. From my calculations at this power and wavelength using approximate standard coating concentrations the exposure time for Kallitype is ~2.6uS.

Calculations are in the exposure calc pdf, currently at rev.A2 If anyone spots any holes let me know. The numbers are the right order of magnitude, based on my current exposure methods and the units work out correctly.

I'd like to thank Mike Ware for providing advice on the calculation methodology for exposure duration.