Dark winter days have a left a blue void, creating a need toward a suitable light source for printing cyanotypes.
Using google for the subject. You find terrible archived forums advocating repurposing UV tanning appliances/bulbs and a blather of pointless arguments on different lighting types.
Setting this rubbish aside I found a small amount of more credible information via books as well as asking artists and friends.
Wavelength of the light source is important. Many of the cheaper light sources are vague and questionable. The apparent magic number often seen is 365nm, while 405nm which is usually used for resin curing does not work, but given the obscurity of some products mileage may vary.
I found a cheap set of LED UV bulbs with a wavelength of 365nm - 400nm. The wattage is 7W and takes around 2 hours to contact print with a desk lamp and negative. This seems to check out, with my friends 13w energy saving UV bulb taking one hour to expose.
Rig up two lights for faster exposure. This could be done with cheap pendent lights and a box. A lid could hold the lights in place allowing for consistent results. I could even use a smart extension plug to time the exposure.
Figure out and dial in exposure. I need to work out a process for creating a suitable negative for cyanotype printing. This is normally done with a curves tool to limit the dynamic range.