Obviosuly the light/exposure is the issue here. A Halogen light gives very little UV in the wavelengths used in iron based processes. You could easily be looking at exposures of around 1hr or more (depending of lots of diffrent factors of course). In the UK here most likely the easiest ones to get are the 'bug killer' bulbs, BL tubes I've always found to be the best but not as easy to source or as cheap. A lot will depends on what size your printing of course and how much you want to invest. As for using the sun - well I get a exposure of about 10mins when I'm down in SW France, or about 20-30mins here on a sunny day. You just often need to wait a few months for one though!
Another thing is - are you using any sufactant in your recipie? If not I think some of problem is the fact that the cyanotype solution is just 'sitting' on the surface of the paper, therefore VERY easily washed off. One thing I can strongly recommend is a tiny amount of sufactant to help the sensitiser just penatrate into the very top surface of the paper, rather than sit on the surface.
The normal one used is Tween 20 (i.e. Polysorbate 20). I would mix up about a 2% solution and maybe add 1 drop of that per 5-10mls of sensitizer just before coating. It may well also help you with the coating process. If you dont have/cant get any Tween 20 try using the same dilution of photo-flo as it will help break the water tension a bit. It's not so great but it might help you see if this is the issue.
Last edited by Taraxacum; 08-01-2013 at 06:54 AM. Click to view previous post history.
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