Cause of Spots Appearing on Salt Prints

[Tom Taylor]

Does anyone have any insight into the cause and prevention of these spots or stains that appear on the back of salt prints that I have been printing?

The only appear about half-way through the final wash – never during the initial clearing, washing, toning and fix stages. I clear in a 3% solution of kosher salt with 1% citric acid for 5b minutes followed by a 15 minute rinse in running water, platinum toning followed by a 6 minute wash in running water, 2 minute fix in 10% sodium thiosulfate, 5 minute rinse in running water, and a final wash of 40 minutes. They appear pronounced on the backside of the paper as shown and occasionally appear very faint on the image side. Paper is Bergger Cot 320.

Thanks,

Thomas

 

[gzinsel]

i'm going to guess, I think its contamination due to one of these many fine "things"/ 1. salt solution is migrating to the back. where/when you are sensitizing salt solution is contaminated with silver nitrate. although not exposed to light. it shows only later.

 

[Prof_Pixel]

Do you stack your salted paper?

 

[Tom Taylor]

Thanks for the replies everyone.

I think that gzinsel's guess will turn out to be spot on. I lightly tape each sheet to a clean sheet of acrylic and leave the sheet taped to the acrylic to air dry face-up. Since I overcoat onto the acrylic I suppose that the sensitizer is soaking into the exposed sides from the acrylic. Next time I coat (hopefully tomorrow) I plan on covering the acrylic with absorbent paper towels and taping the paper to the towel. That way any overcoat should be absorbed by the towels...hopefully.

Thomas

 

[Tom Taylor]

Yep, it turned out that sensitizer from over brushing on the acrylic was soaking into the edge of the paper. I taped a sheet of Bounty to the acrylic and then taped the paper to the Bounty and no stains appeared! But, alas, I don't like the resulting print: There's too much white in the foreground so I have to reshoot it under more favorable conditions - maybe tomorrow or Tuesday.

Thomas