Pt/pd white blobs

scopa · Aug 15, 2021

Hello

after many months of producing pt/pd prints without too many issues I have now run into an problem where the last six prints are covered in white blobs especially in the mid-tones and the highlights are overexposing. In fact, looking at the prints it appears that the issue with the highlights is getting worse!

So far I have tried:

A new batch of Ferric Oxalate
Testing PH of my Potassium Oxalate developer (it's 6).
Filtering my developer
Changing the contact frame
Using a hake brush and a puddle pusher - both produce the same problem
A new pack of paper - Hahnemule in both cases
Completely fresh clearing bath
Using and not using tween

Has anyone had the same problem and, if so, what the solution to this problem?

Alan9940 · Aug 15, 2021

I would suggest emailing Bostick & Sullivan for help. They are very responsive and have a vast amount of experience.

Vaughn · Aug 15, 2021

Print w/ same chemicals, etc but change the paper. That would be my first guess.

nmp · Aug 15, 2021

scopa said:
Hello

after many months of producing pt/pd prints without too many issues I have now run into an problem where the last six prints are covered in white blobs especially in the mid-tones and the highlights are overexposing. In fact, looking at the prints it appears that the issue with the highlights is getting worse!

So far I have tried:

A new batch of Ferric Oxalate
Testing PH of my Potassium Oxalate developer (it's 6).
Filtering my developer
Changing the contact frame
Using a hake brush and a puddle pusher - both produce the same problem
A new pack of paper - Hahnemule in both cases
Completely fresh clearing bath
Using and not using tween

Has anyone had the same problem and, if so, what the solution to this problem?

Seems to me that the defect is all over, not just in the highlights - it might just be less obvious in the shadows. If I enlarge the shadows areas, I see spots in similar size and frequency. Do they look like the so-called "blotches" that everyone dreads about? Checkout the newly revived thread:

https://www.photrio.com/forum/threads/not-happy-with-hahnemuhle-platinum-rag.142805/

:Niranjan.

doughowk · Aug 15, 2021

Coating room humidity? Running AC during Summer?

koraks · Aug 16, 2021

Vaughn said:
Print w/ same chemicals, etc but change the paper. That would be my first guess.

Agreed. This sort of problem is nearly always paper-related. The exact cause is a matter of Higher Paper Science - i.e., we'll probably never know, but switching to another paper usually helps.

Andrew O'Neill · Aug 16, 2021

I had issues with a previous batch of Hahnemuhle PR. Also, my tap water is very alkaline, so for clearing my kallitypes, I have to put in a wee bit of vinegar. Acidifying the paper may help. I have also gotten into the habit of putting one drop of Tween in the sensitiser, and letting the coated paper air dry. I used to hit it with a blowdryer. Stopped that insane practice.

TheFlyingCamera · Aug 16, 2021

Andrew O'Neill said:
I had issues with a previous batch of Hahnemuhle PR. Also, my tap water is very alkaline, so for clearing my kallitypes, I have to put in a wee bit of vinegar. Acidifying the paper may help. I have also gotten into the habit of putting one drop of Tween in the sensitiser, and letting the coated paper air dry. I used to hit it with a blowdryer. Stopped that insane practice.

I blowdry my coated paper, but only with the cool air setting, and only long enough to get it surface dry to the touch.

But this mottling doesn't look like a blowdryer issue. This looks like most likely a paper issue, as others have said. Other things to look at:

make sure the glass in your contact frame is clean.
don't know what media you are using for your negatives - if these are in-camera originals, examine your film to verify it doesn't have water spots. If digitally enlarged negatives, look very closely at your transparency medium and make sure it is free of defects.

scopa · Aug 16, 2021

Thank you all for your replies.

With regards humidity I live in the West of Scotland so my ambient humidity is 70%-90%
I always air dry my sensitized paper, never blowdry.

I ran a test print, tonight, on Bergger Cot320 and there is no mottling so the cause was the paper. Bergger doesn't seem to clear as well with EDTA/Sodium Metabisulphate so I'm going to change to a 3 x citric acid bath and switch to using this paper going forwards. It's a shame because I liked Hahnemule but the image on Bergger is sightly warmer so is perfect for my prints.

Thank you all for your contributions and assistance.

scopa · Aug 19, 2021

Update

Short version: it wasn't the paper. It was the clearing bath

Long version: the following day after the previous post I checked the Bergger print again and found that the mottling was still present, although much reduced. Applying the principle of only changing one thing at a time I did another print with the citric acid 3 x bath and checked the print the following day to see no mottling but there were now slight yellow stains so did another print, with Hahnemule and it was all good.

Looking back over my notes I saw that I had opened a new tub of sodium metabisulphite (same CAS number as sodium sulfite from B&S) and tipped the end of the old one into it. The first few prints would have used the residue of the old batch and then the new one would have come into use and it would seem that that is the cause. I've ordered a new tub of sulphate and will throw the other one away.

fgorga · Aug 19, 2021

scopa said:
Update

Short version: it wasn't the paper. It was the clearing bath

Long version: the following day after the previous post I checked the Bergger print again and found that the mottling was still present, although much reduced. Applying the principle of only changing one thing at a time I did another print with the citric acid 3 x bath and checked the print the following day to see no mottling but there were now slight yellow stains so did another print, with Hahnemule and it was all good.

Looking back over my notes I saw that I had opened a new tub of sodium metabisulphite (same CAS number as sodium sulfite from B&S) and tipped the end of the old one into it. The first few prints would have used the residue of the old batch and then the new one would have come into use and it would seem that that is the cause. I've ordered a new tub of sulphate and will throw the other one away.

Be very careful with your chemistry... sodium metabisulfite (Na2S2O5) is not the same compound as sodium sulfite (Na2SO3). Therefore, if you really have packages of each of these compounds one of them is mislabeled.

Furthermore, you say that you have ordered a new tub of "sulphate"... please be aware that sulphate is not a replacement for metabisulfite nor for sulfite. These three species are quite distinct chemically and can not be substituted for each other in the large majority of applications.

scopa · Aug 19, 2021

Sorry, meant sulphite and not sulphate.

fgorga · Aug 19, 2021

scopa said:
Sorry, meant sulphite and not sulphate.

Good!

I am not an experienced Pt/Pd printer... salted-paper is my current passion... but as I understand the Pt/Pd process sodium sulfite is correct compound for this application.

scopa · Aug 20, 2021

What I do not understand is how the sodium sulphite from B&S and the metabisulphite from apcpure.com both have the same CAS number of 7681-57-4 but that might just be my lack of knowledge of how these things work.

koraks · Aug 20, 2021

Then something is being mislabeled. Sulfite and metabisulfite are very different things and I doubt you can substitute one for the other in this application.

scopa · Aug 20, 2021

Interestingly looking at the CAS https://chemicals-direct.co.uk/product/92857-sodium-metabisulfite-reagent-grade-99/?gclid=Cj0KCQjwpf2IBhDkARIsAGVo0D2b4aJrUcA5swDq2prveS9Q3vpxu0go22zdAMCTmzk6XmQWz8ZmqmoaAlHOEALw_wcB it shows it as metabisulphite so it appears that the B&S one might be wrong.

Like I said, I have no knowledge on this so it could well be me misunderstanding something.

koraks · Aug 20, 2021

I checked the Bostick & Sullivan website, but I don't see an error if I look at the 100g listings of both sulfite and bisulfite. They're both listed with the appropriate CAS#. Also, on apcpure.com, both listings of metabisulfite are accompanied with the correct CAS #.

Can you provide a link to the supposedly erroneous information?

scopa · Aug 20, 2021

scopa · Aug 20, 2021

That's the bottle which was supplied by B&S. I just spotted that it's bisulfite and not sulfite so that's my mistake. However, aren't bisulfite and metabisulphite different?

fgorga · Aug 20, 2021

That jar is mislabeled. Sodium bisulfite (aka sodium hydrogen sulfite) has the formula NaHSO3 and a CAS number 7631-90-5 and is a different sodium metabisulfite. The CAS number on that jar is, as you say, for sodium metabisulfite. Thus there is definitely a mistake here.

If that jar really contains the bisulfite you can probably substitute it for sulfite in a recipe.

When either sodium sulfite or sodium bisulfite are dissolved in water the resulting anion is the same... sulfite SO32-. The composition vis-a-vis the cations will be a bit different as will the concentration of the various species, but in all likelihood the solution should work as intended.

Specifically, a solution made subistuting and equal weight of sodium bisulfite for sodium sulfite will have a lower pH, a bit higher concentration of sulfite and a lower concentration of sodium than the solution made from sodium sulfite.

As said previously by me and others, metabisulfite is chemically very different from sulfite and most likely you can not substitute one for the other.

fgorga · Aug 20, 2021

scopa said:
That's the bottle which was supplied by B&S. I just spotted that it's bisulfite and not sulfite so that's my mistake. However, aren't bisulfite and metabisulphite different?

I was writing my more detailed reply when you wrote the above.

To answer your question directly... you are correct. Bisulfite and metabisulfite are NOT the same!

See my previous reply for more details.

scopa · Aug 20, 2021

Thanks for your reply and clarification. I now feel slightly less stupid because it wasn't entirely my mistake. I simply took it that the CAS number on the label was what I had to order and that the name was simply a difference between American English and English English. My take away from your reply is to prioritise the chemical name and research further if in doubt.

fgorga · Aug 20, 2021

scopa said:
Thanks for your reply and clarification. I now feel slightly less stupid because it wasn't entirely my mistake. I simply took it that the CAS number on the label was what I had to order and that the name was simply a difference between American English and English English. My take away from your reply is to prioritise the chemical name and research further if in doubt.

Chemical nomenclature can be tough, even for us chemists. "Bisulfite" is an antiquated term.the modern term is "hydrogen sulfite". The modern term is a bit more descriptive and less ambiguous, at least to a chemist, but I digress! Unfortunately, photographers seem to be stuck in the late 1800s/early 1900s when it comes to chemical nomenclature. This often leads to confusion.

Having a mislabeled bottle doesn't make things any easier!

Glad things are straightened out.

koraks · Aug 20, 2021

fgorga said:
When either sodium sulfite or sodium bisulfite are dissolved in water the resulting anion is the same... sulfite SO32-. The composition vis-a-vis the cations will be a bit different as will the concentration of the various species, but in all likelihood the solution should work as intended.

Which is likely why it was mislabeled. I wouldn't be surprised if at least 50% of the jars of 'bisulfite'/'bisulphite' are mislabeled this way.

scopa said:
I now feel slightly less stupid because it wasn't entirely my mistake.

Nooo...but you said they swapped sulfite and bisulfite (or metabisulfite). That's quite a different matter, and much more significant for photographic purposes, than the fairly innocuous mistake of selling metabisulfite as bisulfite or vice versa.

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