Uneven Blotches on Salt Prints: Could This Be Measles'?

I’m getting some uneven blotches on my salt prints, mostly visible in the darker parts of the image. They’re not pure white spots, but slightly lighter patches that appear randomly. Could this be what’s referred to as “measles” in historical descriptions of salted paper prints?

For reference, I’m printing on Hahnemühle Platinum Rag, salted once and sensitized once. When applying the silver nitrate solution, I add two drops of citric acid. I also fix the prints in two separate baths, each for 6 minutes. These prints are gold-borax toned. Interestingly, on thinner papers than this one, the unevenness is not as noticeable.

If this issue comes from uneven application or absorption, would it make more sense to try two coats of the salting solution or two coats of the silver nitrate solution?
Any advice or experience with this type of uneven brightness would be greatly appreciated.

Do you have any Tween 20, or Photo-Flo? If not, trying soaking the paper first in distilled water, and drying it before sensitising. I find the paper (both HPR, and Revere P) to respond better to coatings by doing this, rather than taking the paper straight from the package.
If this doesn't help, I'd try mixing up a fresh Silver Nitrate solution...

Andrew O'Neill said:

trying soaking the paper first in distilled water, and drying it before sensitising.

Click to expand...

I can see how this might help, yes.

I think this is one of those complex interactions between the sensitizer and the constituents and fabric of the paper that are hard and sometimes impossible to really resolve. My workaround is usually to avoid papers that give such problems.

Btw, the sensitization process might benefit from some optimization; for instance, there's this very high density area in the top right where the sensitizer apparently pooled.
I would also recommend printing (at least for tests) with a masked border so you know the print properly clears. Salted paper in particular is extremely prone to fogging in the highlights.

HPR works quite well with the salt process. I have found that it's not so great all the time, fresh from the package. The pre-water bath seems to soften the fibres, and allow better sensitiser penetration. But... I could be wrong in this case, though. It could be more of a chemical thing, rather than a paper thing.

HPR is my "go to" paper for salt prints.

I use 1 drop of 10% Tween-20 per 10 drops of sensitizer and have no trouble with unevenness in my prints..

Andrew O'Neill said:

HPR works quite well with the salt process. I have found that it's not so great all the time, fresh from the package. The pre-water bath seems to soften the fibres, and allow better sensitiser penetration. But... I could be wrong in this case, though. It could be more of a chemical thing, rather than a paper thing.

Click to expand...

Thank you so much!
I have some Tween, so I’ll give that a try.

Regarding the distilled water soak — is it okay to completely immerse the paper in distilled water, say for about five seconds, and then let it air-dry for a day before using it as usual?

Also, since I believe you’ve done photographic work in Japan as well, are there any papers available here besides HPR that have worked well for you?

koraks said:

I would also recommend printing (at least for tests) with a masked border so you know the print properly clears. Salted paper in particular is extremely prone to fogging in the highlights.

Click to expand...

Yes good idea.
Since Rubylith isn’t available here in Japan, I’ll try making a border using aluminum foil instead.

Thanks for your comments.
I’ll start by trying the Tween.
Eventually, I’d also like to experiment with albumen printing — do you think HPR might be too thick for albumen prints?

D_Quinn said:

Thank you so much!
I have some Tween, so I’ll give that a try.

Regarding the distilled water soak — is it okay to completely immerse the paper in distilled water, say for about five seconds, and then let it air-dry for a day before using it as usual?

Also, since I believe you’ve done photographic work in Japan as well, are there any papers available here besides HPR that have worked well for you?

Click to expand...

5 sec isn't enough time to allow for the fibres to soak up water. I soak the paper in room temperature distilled water for 3 min., then air dry. It usually takes a couple of hours to dry, as long as the RH isn't high...or else the dehumidifier is hauled out!

Andrew O'Neill said:

5 sec isn't enough time to allow for the fibres to soak up water. I soak the paper in room temperature distilled water for 3 min., then air dry. It usually takes a couple of hours to dry, as long as the RH isn't high...or else the dehumidifier is hauled out!

Click to expand...

I tried it today, and after doing the water soak, the unevenness disappeared and I was able to get a good, rich density.
I also tested using Tween 20 alone, but it still showed some uneven areas.
It seems that the water soak works best for me.
Thank you so much!

Great!

Perfect! Having thought about this a little more, I wonder if perhaps the paper was simply too dry. Off the top of my head, the 'standard' moisture content for dry paper is around 16%, but it can of course be dried even further under certain conditions. The moisture content of a paper can greatly affect the way it accepts a coating. A very slightly moist paper will readily soak up a water-based sensitizer, usually very evenly as well.

Why not combine water soak and salt coating into a single step of floating the paper in the salting solution? Is there a reason not to do that?

Raghu Kuvempunagar said:

Why not combine water soak and salt coating into a single step of floating the paper in the salting solution? Is there a reason not to do that?

Click to expand...

Now that you mention it, this is pretty much what I do...

I soak paper in the salting solution, let it dry and then store it in zip-lock bags. I often salt many sheets at once. Stored in the tight sealing plastic bag, it lasts 'forever' (well at least for many months!).

Anyway, @D_Quinn I am glad that you have resolved the issue.