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Testing Coating Area and Ferric Oxalate

Whenever you set up a new coating area be sure to test for light fog!

Coat (with fresh Ferric Oxalate) and dry a sheet of your normal paper. After you dry it put paper face up on coating area and cover part of the paper with a cup etc. and leave for 5 to 10 mins. Then develop, clear , wash and dry normally. If you see any image on paper after it is dry then you most likely have too bright a coating area. If the images goes to a grey tone you have a fogging problem caused by old ferric oxalate or too much light in coating area. If the images goes to yellow you have not cleared the paper fully.

FERRIC OXALATE, FOG AND CLEARING TEST

Prepare paper to make print for your normal contrast. Do everything just like you would to make a print except don't expose paper!

After paper has been dried, develop unexposed paper, clear wash and dry paper your normal way.

If you see any noticeable color or density where emulsion was applied to paper one of 3 things is possible:

1. The light you use while coating is too bright or somehow you have fogged the paper. You'll see more grey than yellow density.

2. Ferric oxalate is old. You can give it a little jazz by adding a few drops of hydrogen peroxide to ferric oxalate #1 or #2. But I'd throw it away!

3. Your clearing bath method is not effective. This could be due to time in baths, weak or over used baths or the chemicals your using, etc. etc. you'll see more yellow than grey density.

Remember:
Yellow stain= chemical stain or bad clearing
Grey "stain"= fog density buildup