>
> Here are some test results re washing cyanotypes.
>
> Whatman Watercolour paper was coated with new cyanotype sensitizer (this
> uses ferric ammonium oxalate rather than the citrate).
>
> The paper was cut into four test strips which were separately exposed for
> two minutes using the same step wedge and Cosmolux UV 40W fluorescent tubes
> with internal reflectors. Unfortunately owing to operator error with the
> timer (I forgot to reset the counter) one strip was slightly underexposed.
>
> The test strips were rinsed in four different solutions for 10 minutes:
>
> 1. 2% sodium chloride (iodised table salt with an anticaking agent, if that
> matters)
> 2. 2% citric acid (I bought 500 gm at a health food shop)
> 3. distilled water
> 4. Canberra tap water (used the underexposed strip, so this isn't really
> valid).
>
> The strips were then further washed in tap water (no hydrogen peroxide) and
> air dried.
>
> I'd say there's very little difference between distilled water, tap water,
> and the salt solution (salt water might be just barely better), but the
> citric acid does show significantly darker blues.
>
> The citric acid solution does need frequent changing with this paper (maybe
> I overcoated or didn't use enough solution - some of the prussian blue
> seemed to be floating off in the water and staining the whites, especially
> the back of the sheet).
>
> As they say, your water supply may vary, but as per Mike Ware's article on
> new cyanotype (Ag+ Photographic, vol. 7 (1995) p. 79), a 1 or 2% citric acid
> wash aid for cyanotype is definitely worth trying. It doesn't have to be too
> exact - 1 level teaspoon weighs 5 gm which is about right for every 250 mls
> of water; 2 level tablespoons are about 20 gm which is rough enough for a
> litre.
>
Philip, wherever you are (after 2 days you're going to have 73 messages
in your inbox -- at least!):
I'm fascinated by your tests, which need I add gave some different results
from mine? That's on the citric acid wash, which I found stained the
whites so heavily that the prints were nearly illegible. Whether the blues
in the shadows were darker, I didn't especially notice -- I had just begun
doing cyanotype and, lacking this list or any other useful discourse, was
more or less stumbling in the dark. My guess would be, however, that if
you subtracted the same amount of blue that had been added to the whites
from any extra blue added to the darks, it would have been, so to speak, a
wash.
However mine was on different paper, and with a different cyanotype
formula (plain old ferric ammonium citrate & potassium ferricyanide) and
presumably that is an important difference.
Meanwhile, it occurs to me to wonder if the "regular" formula on the same
paper without the citric acid wash would be darker or lighter than your
formula (is that Mike Ware's new cyanotype you're using?) with the citric
acid wash...... tho of course, this way lies madness......
Judy