first cyanotype, indigo blotches?

Hi!

I just had some fun with cyanotypes. The first two attempts came out OK, first one underexposed, the other one, a 40 minute exposure, turned out like this:

Dead Link Removed

The third attempt was dissapointing. I have put together 11 6x6 negs as a little experiment, please check the attachment. I don't have a LF camera, so this was a "cheapo" way to get slightly larger cyanotype.

Anyway, I coated a paper, let it dry about 20 minutes (maybe not fully), placed the cut up/taped up negs on the paper, put between the 5 mm glass sheets and exposed for 46 minutes. When I rinsed the paper I saw big areas that were indigo colored, ie more blue than the rest of the picture, that were not in the negs. I would call them blotches. I will scan this soon, but the print is drying in the darkroom.

I'm thinking this could be the problem:

1. Not dry enough paper.

2. Not enough pressure on the negs and paper, ie negs weren't in perfect contact with the paper.

3. Overexposure.

Any tips?

BTW, this is what I use. 300 watt UV-bulb from OSRAM, called "Ultra Vitalux". It was placed about 40 cm from the glass. As a "frame" I use two 5 mm sheets of glass. I should get something to really hold the glass sheets together tightly, right? Do I need a more powerful UV-lamp?

Thanks!

Maybe where you've touched the paper. No authority on these things but I decided to coat the whole piece of paper (little ones suitable for 4x5 negs) and I got splotches on the edges where I think I was holding the paper to stop it moving while coating. I had some kind of gloves on at the time, but when creating the neg sandwiches once they'd dried I didn't have the gloves on so could have caused it then. As they were only on the edges, I could chop them off and you'd never know

You may want to try letting the paper dry fully and then compare, as well as watching for finger marks.

Thats a really great image, and resourceful.

I got that type of thing when the paper hadn't dried fully.

psvensson (Peter?),

thanks, the blotches are much better now on the dry print. See the attachment. You can see the faint areas of blotchiness in the middle of the print.

So far, the contrast of my cyanotypes is extreme. These negs are quite dense, but not so high in contrast. I don't expect any detail in the window, but the walls and the cover should have some I think. Acidic first bath could help maybe? Is lemon juice OK? I can't really buy any acid, unless you can find it in a grocery or hardware store.

I will do a new try on this one, with drier paper, flatter negs and more time.

Looks like uneven drying before printing to me.

You should be able to purchase white vinegar in a grocery. White vinegar is basically weak (~4% IIRC) acetic acid. That will work to acidify rinses. Citric acid is sometimes sold where they sell canning supplies. Either should work.

Joe

Standard white vinegar in the USA and Canada is 5% acidity; diluted 1:3 it's just right for stop bath (though more expensive than Kodak or Ilford indicating stop baths). I'd dilute about 1:31 (an ounce per quart) to use it in a cyanotype first bath; you want it just barely acidic, to kill any alkalinity that might be present in your water.

BTW, that blotchy area does look a lot like what I've seen where I left liquid sensitizer on a piece of paper and it dried extra thick; perhaps an area of overlap in your brush coating?