Mike Ware Cyanotype Problems

I am using Mike Ware's New Cyanotype and Arches Watercolor paper. The past few times I have tried to print I have not been getting the reversal in tones it usually does when it is almost done printing. It bleaches out to a light blue, but seems to halt right there. Does anyone know if the sensitizer gets old and loses some of its potentcy? Or is it the paper? Or is it just too early to try printing, even if it is sunny and clear? Or am I just going nuts? Your input would be most appreciated.

Drew

First, no, I don't exactly remember whether I once consciously experienced sensitizer gone really off. It does tend to become more bluish with the time if you do not add any dichromate, and I once filtered a rest of old sensitizer, added some dichromate, and as far as I remember it still printed well.
However, I would not consider Arches Watercolour a very good paper with New cyanotype. As far as I know, it has alkaline buffers, and I would first immerse the paper, before using it, in a 1-2% acid (acetic, citric, oxalic) for about 5 minutes or until the bubbles stop coming, wash the paper out in pure water, dry, use. Even then, I am not certain that this paper will work for this process.
Oh yes: does the coating stay yellow when dry or does the colour change to green?
What contrast are you trying to get/how much dichromate do you add? With too much the picture becomes grainy and, of course, very slow to print.
I seem to have noted that too much humidity in the air/paper is bad for New Cyanotype: blotches appear in the print-out.

Lukas Werth said:

However, I would not consider Arches Watercolour a very good paper with New cyanotype. As far as I know, it has alkaline buffers, and I would first immerse the paper, before using it, in a 1-2% acid (acetic, citric, oxalic) for about 5 minutes or until the bubbles stop coming, wash the paper out in pure water, dry, use. Even then, I am not certain that this paper will work for this process.
Oh yes: does the coating stay yellow when dry or does the colour change to green?
What contrast are you trying to get/how much dichromate do you add? With too much the picture becomes grainy and, of course, very slow to print.
I seem to have noted that too much humidity in the air/paper is bad for New Cyanotype: blotches appear in the print-out.

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The coating turns a lovely verdant green. In other words, bad. But my sensitizer is green anyways, so I am not sure about that. The buffering in the paper sounds like a likely explination. It makes more sense than weak sunlight. I have not added very much dichromate at all. I don't think I added any, but I can't quite remember. As for the blotches, they seem to apper anyways even after drying and before exposure. Very unsightly. I will probably switch papers. I was having more luck with strathmore, but I might try something else. Any suggestions?

Drew

Green means the paper is bad, and this is exactly what I would expect with untreated Arches Aquarelle. I know that the sensitizer looks greenish when it comes out of the bottle as a fluid, , but when coated it has to be and remain bright yellow, and this process is very sensitive to paper (have you read Mike Ware's instructions on his website? If not, I would strongly advise you to do so).
I regularly print on Fabriano Artistico, but only after treating it in acid the way described. This way your results should be of first quality. If you do not want this, try Arches Platine, but the problem with this paper is that it used to react negatively with dichromate (it turns very grainy; I have not used this paper for quite some time, so this might have changed, but I would not bet on it).

Arches Aquarelle may or may not work treated with acid; blotches or unwanted grain appear with quite some papers I tried even after acid bath.