Hahnemuhle Platinum Rag Cyanotype coating issues

Andrew Keedle · Feb 23, 2021

Hey, I'm having problems with coating Platinum Rag with a Mike Ware Cyanotype solution. I can coat this same solution on Arches Platine and Bergger COT 320 with no troubles. I've tried lots of things. Different brushes, coating rod, no Tween, varying amounts of Tween, air drying for several hours, hot air drying. Although the paper appears to coat evenly and looks fine when dry as soon as I expose you can see the issues even before "deving" in either water or 1 - 3% Citric Acid.

My last attempts were with 3 drops of 20% Tween 60 in 2ml of solution and 1 drop of 60% Tween 60 in 2ml of solution for an x10 paper. Obviously the dilutions and drop sizes of the different Tween dilutions is a big variable. If I've used that amount of Tween on any other paper the solution has pretty much soaked in straight away and saturated a small area and not been able to coat completely.

I've been using the same exposure time and (digital) negative as I would for Bergger COT 320. I'm so confused. Anyone able to shed any light on what I have done wrong.

awty · Feb 23, 2021

Looks like something is wrong with the chemistry. Maybe try just the original formula with out any additives a clean brush and if there is mottling paper must be contaminated..
I usually get that on cheap paper I havent pre processed properly and using a wetting agent. Wetting agents are finicky some paper react bad.
Never had an issue with Platinum Rag and consider it the best of all papers, wish I could get it locally. I just brush my emulsion on after humidifying the paper.

Andrew Keedle · Feb 23, 2021

Thanks Paul. How do you humidify your paper?

Andrew O'Neill · Feb 23, 2021

Coat some Arches Platine and see if you get the same issue or not. I only ever had issue with HPR if the RH was way too high or too low. I've never had to use Tween. I'm assuming your cyanotype solution is fresh? Sorry, I've only ever used the traditional formula.

nmp · Feb 23, 2021

Are these the dreaded "splotches?"

Check this thread, also on HPR:

https://groups.io/g/altphotolist/to...,0,0::recentpostdate/sticky,,,20,2,0,80693359

:Niranjan.

Vaughn · Feb 23, 2021

Thanks for the info -- I use HPR for develop-out Pt/Pd printing, which does not seem to be part of the blotching issue. I was getting worried -- I got a big roll of it and will be printing 5.5x14 and 11x14 this week. But not too worried as I have printed with it already.

Andrew Keedle · Feb 24, 2021

That's really useful info Niranjan, thanks. I've tried another brush (which I think was contaminated) and with considerably less sensitizer and things look ok. I think I was going down a spiral of adding more sensitizer and Tween as the coating was just sloughing off which leads to it crystallising. Fingers crossed that was the problem.

nmp · Feb 24, 2021

Andrew Keedle said:
That's really useful info Niranjan, thanks. I've tried another brush (which I think was contaminated) and with considerably less sensitizer and things look ok. I think I was going down a spiral of adding more sensitizer and Tween as the coating was just sloughing off which leads to it crystallising. Fingers crossed that was the problem.

You're welcome. I can see how cyanotypes can entice you into a rabbit-hole. Often simple answers are the correct one - at least we would hope so.

Good luck!

:Niranjan.

removedacct1 · Feb 24, 2021

Try sizing the paper with Arrowroot Starch. I did that last summer as an experiment, and the difference was startling: I got shadow area blues so deep they were almost black, and no artifacts.

nmp · Feb 24, 2021

paulbarden said:
Try sizing the paper with Arrowroot Starch. I did that last summer as an experiment, and the difference was startling: I got shadow area blues so deep they were almost black, and no artifacts.

Hi, Paul: I got some arrowroot from Formulary some time ago and just thinking of doing something with it. What is your application process, dilution etc. Any tips?

Thanks.

:Niranjan.

removedacct1 · Feb 24, 2021

nmp said:
Hi, Paul: I got some arrowroot form Formulary some time ago and just thinking of doing something with it. What is your application process, dilution etc. Any tips?

Thanks.

:Niranjan.

I used the default sizing packet that came with a box of Formulary Van Dyke Brown I bought a couple years ago (and hadn't used): I mixed it as instructions indicated and applied it with a disposable foam brush. It worked beautifully. It resulted in significantly better image quality and eliminated "paper quality issue" I'd had to date.

awty · Feb 24, 2021

Andrew Keedle said:
Thanks Paul. How do you humidify your paper?

With steam.

Andrew Keedle · Mar 11, 2021

Hey, I came across a video on Bill Schwab youtube channel talking about acidifying his Tween. Apparently its very Alkaline and needs to be mixed with an acidic solution. He was having problems with clearing. He uses 1% Oxalic acid at 1:1. I don't have that so I tried 2% Citric acid at 1:1. Seems to have fixed the problem so far.

Andrew O'Neill · Mar 11, 2021

Clever!

fgorga · Mar 11, 2021

I'm glad that you and the fellow in the video have found a system that works for you... it the end that is all that matters.

However, Mr. Schwab clearly knows no chemistry. He lost me when he attempts to measure the pH of Tween. The concept of pH is only valid in aqueous solution. Tween 20 straight out of the bottle contains no water. Thus, although one can "measure " its pH the result is meaningless. I persisted in watching the entire video and it is rife with other chemical errors that I'll not bother to list or refute.

Again, I'm not disputing the fact that adding a bit of acid to the Tween is useful in this process. I have no experience with this. However, his accompanying chemical reasoning throughout the video is mostly just plain wrong.

nmp · Mar 11, 2021

fgorga said:
I'm glad that you and the fellow in the video have found a system that works for you... it the end that is all that matters.

However, Mr. Schwab clearly knows no chemistry. He lost me when he attempts to measure the pH of Tween. The concept of pH is only valid in aqueous solution. Tween 20 straight out of the bottle contains no water. Thus, although one can "measure " its pH the result is meaningless. I persisted in watching the entire video and it is rife with other chemical errors that I'll not bother to list or refute.

Again, I'm not disputing the fact that adding a bit of acid to the Tween is useful in this process. I have no experience with this. However, his accompanying chemical reasoning throughout the video is mostly just plain wrong.

I also wondered, when I saw the video for the first time, how much really is T-20 used to make any significant change in the acidity of the sensitizer. I put one drop of 10% T-20 per ml of sensitizer that comes to about 0.2% w/v. I just checked a 10% T-20 solution on my pH paper and if anything it seems to be acidic - turned reddish immediately but then faded to paper color which signifies 6 or higher.

Perhaps addition of acid itself that does the trick here. But like you said, if it works then it works.

:Niranjan.

Andrew Keedle · Mar 12, 2021

Thanks gents. I have no idea about the chemistry but it appears to help in my circumstances. No idea why...

nmp · Mar 12, 2021

Andrew Keedle said:
Thanks gents. I have no idea about the chemistry but it appears to help in my circumstances. No idea why...

What is that saying - don't look at the gift horse in the mouth...

Hahnemuhle Platinum Rag Cyanotype coating issues

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Andrew Keedle

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fgorga

nmp

Andrew Keedle

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Hahnemuhle Platinum Rag Cyanotype coating issues

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