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banana_legs
09-30-2009, 06:48 PM
In an effort to save the planet (and money), I have been attempting to make my own re-cycled paper. I have used copier paper as the basis; when I update my lectures the old master copies of the notes make a good source of fibre. I have now pretty much got the knack of making good 8"x10" sheets and sorted out a work-flow for getting it flat and sizing the paper so that I can do a decent cyanotype.

The problem I have though is that the yellow sensitiser in low-exposure areas is really stubborn to wash out; I have also noticed that the print is a touch more purple/blue than I usually see. I tested a sheet for pH (1gram paper mashed into 50ml of distilled water) and it came out as a pH of 9! I use PVA glue in the pulp stage as internal sizing and my final surface size coat is a mix of gelatine and alum which should be slightly acidic. I think the washing phase of the print is being influenced by the body of the paper as the print develops as a normal blue but then goes more purple and fades the longer I wait for the yellow to wash out. Acid washes are better but the long-term prospects for the image may be in question as the pH is so high.

Does anyone know if the problems of washing the yellow sensitiser stain out is likely to be linked to the pH of the paper or is it an issue with the gelatine of the size? The size is preventing the sensitiser (about 1.5ml per 8x10 sheet) from soaking into the paper so I do not think it is an issue with the quantity of sensitiser.

Does anyone have experience with trying to reduce the alkalinity of paper? I have the opportunity to adulterate the paper in the pulp stage too, rather than just the finished sheets.

Regards,

Evan

earlj
09-30-2009, 07:04 PM
Evan:

High ph is the enemy of cyanotype. When you tone a cyanotype, you soak it in ammonia or sodium carbonate, and the image gets completely bleached. I have had difficulty printing cyanos on paper that is sized with alkaline buffers. If you let the paper sit after you have sensitized it, but without exposing, does the sensitizer turn green? (It will almost always turn green if you leave it long enough, but it should stay bright yellow for at least 12 to 24 hours). If it does turn green, then this indicated chemical fogging, and I have found that paper that exhibits this behavior will not work for cyanotype. You can't get it to clear in the unexposed areas, and the contrast is reduced due to the spontaneous fogging.

I have heard of people soaking paper in citric acid solution prior to printing with cyanotype, but your paper sounds like it has a bigger problem than this would solve. Can you find a binder for your paper that is acidic to begin with? Have you tried a bit of citric acid in your gelatin size?