Comparing Baohong Master Watercolor to Hahnemuhle Platinum Rag

drew tanner

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Using my Cirkut camera, I make panoramic prints that are about 10” wide by up to several feet long. This limits my choice of paper stocks. I’ve enjoyed the consistency and tonality I get with Hahnemuhle Platinum Rag for vandyke prints. The only catch for me with the Hahnemuhle is wrestling the 50” wide roll to cut such wide prints cleanly/consistently. I recently discovered Baohong Master Watercolor, which comes in conveniently-sized 10.6” by 32’ rolls and is quite a bit cheaper. Both are hot-press, 300gsm 100% cotton papers. I’m not sure if the Baohong is going to be my go-to for exhibit-quality prints. However, for proofs, tests, working prints, etc., it seems promising. It does have a bit of a yellow cast in the highlights compared to the crisp whites of the Hahnemuhle. I’m curious if some of the veteran Vandyke/argyroptype/kallitype printers here have any tips for reducing such a color cast and making the highlights whiter in these iron-based processes.

Here are a couple of step-wedge tests comparing the two. Other than the yellow-ish cast of the Baohong, they’re pretty comparable in terms of density range. I’ll share comparisons of an actual print soon.

 

koraks

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The yellow cast is likely caused by a calcium carbonate buffer that reacts with the iron sensitizer to form insoluble iron hydroxide (a.k.a. rust).

Have you tried soaking the paper in an acid bath prior to use? Popular acids used include citric acid and sulfamic acid, but in principle, many common acids will be suitable. I generally don't do this because I feel it's a lot of fuss while I might as well use a more suitable paper to begin with. But in your particular use case with the very long prints, I can see why you'd want to employ every option available.

There are papers on the market that are little known, but end up being very suitable for alt. process printing. I can only encourage experiments to see what works. I've encountered several 'pearls' that cost a fraction of the big, well-known ones that command a premium.

drew tanner said:
they’re pretty comparable in terms of density range
Click to expand...

The range seems shifted a bit towards the faster side for the Chinese paper. This may be due to the calcium carbonate buffer. But some papers print a little 'faster' than others, necessitating a small adjustment in exposure. In any case, I'd re-do this test with the acid-treated paper to see how this affects the printing characteristics. There's a chance it'll shift back closer to the Hahnemühle.
 
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drew tanner

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This is really helpful, Koraks. Thank you. I use citric acid to clear my vandykes, so I buy it in 8-lb (3.6kg) jugs and have plenty of that to start. Would you recommend, say a 5% solution? I'll redo the test with the acidified paper and report back.
 
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Carnie Bob

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I use this for clearing gum prints I always use it at the very end of a printing session where I notice yellow stain from Ammonium Dichromate.

This may or may not be of any use to the OP now that I think about it. PE gave me this and another clearing bath formula years ago.
 

koraks

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Carnie Bob said:
This may or may not be of any use to the OP now that I think about it.
Click to expand...

It won't help; which is why I asked. I suspected your application was about clearing dichromate stain (it also works to an extent on many kinds of food stains, coincidentally). But it does nothing at all for cleaning ferric hydroxide stains. The bisulfite clearing bath is also used as the second half of the DAS stain clearing routine used in UltraStable. The first step is a weak solution of permanganate. None of this is relevant to Van Dykes and Kallitypes, however.
 
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drew tanner

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I finally got around to repeating my test with the Baohong. @koraks’ advice to acidify the paper did the trick. Here’s a photo of step wedge tests showing plain Baohong, acidified Baohong, and Hahnemuhle Platinum Rag. The mottled mid tones on the acidified Baohong is likely because I added a little too much acid to my sensitizer in attempt to clear up some silver precipitate. Otherwise, I think the paper is a keeper. It’s nice to have it in a size that can simply be cut to length for Cirkut panoramic prints.

 

koraks

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That looks great! Nice to hear the acidification helped.
drew tanner said:
The mottled mid tones on the acidified Baohong is likely because I added a little too much acid to my sensitizer
Click to expand...

Ah, yes, although in part this can very well be a side-effect of acidifying the paper. Unless you wash the paper thoroughly after acidifying it, some of the acid will remain in the paper. It'll be equivalent to adding acid to your sensitizer. I do recognize the grainy look of Van Dyke that's on the acidic side.

You could try soaking the paper in a weak acid solution as you've been doing; 10 minutes or so should do the trick (maybe even less; IDK how fast it'll go). Then wash it in a couple of changes of water to get rid of most of the acid. See if that makes a difference w.r.t. the grainy midtones.
 
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drew tanner

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Thank you. The paper was soaked in a tray of 1% citric acid solution for 10 minutes, then washed in a tray with a Kodak tray siphon for about 30 minutes.
 

koraks

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Oh, great job! Well, there's nothing I could suggest to improve over that; very thorough indeed. I assume in that case that a sensitizer with a little less acid should give smoother midtones. Although paper does have an influence; some papers just don't print quite as smoothly as others.
In any case, the clear highlights are a great improvement in my view!

PS: come to think of it, there's one more thing you could try (if you're not already quite happy with what you've got, of course). I imagine that a light sizing with something like gelatin or perhaps even simply arrowroot etc. could make a difference and result in smoother prints. But it's just a hunch.
 

fgorga

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With regard to the time needed for the acid to react with the carbonate...

Just look at the paper carefully and watch for it to stop fizzing. The reaction between an acid and carbonate generates water and carbon dioxide. The carbon dioxide, being a gas, bubbles out of the paper. When the bubbling has stopped the carbonate is gone.

With most papers I have used two or three minutes is plenty of time in the acid.

One can use this 'fizz test' to check the capacity of your acid solution. If you put a sheet of paper into a spent acid solution it won't fizz and you'll need to replace the solution.

Leaving paper too long in either the acid or even just water can be bad if the soaking starts to affect the sizing in the paper. How long is too long? Hard to say but shorter is definitely safer.
 
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