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  1. #1

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    Michael is back! Jorge is back! & I notice Don is helping someone in the Gallery! I just can't let these wonderful resources go to waste... This posting has been languishing on the other site with no replies and I would appreciate some assistance, I want to size some paper (real paper not my usual 'experimental' stuff)... so....

    Oxalic Acid for sizing papers for Pt/Pd..... Is the formula for a 1% solution based upon weight or volume....... Eg. 1gram of Oxalic Acid to 100 ml of H20. Is this one shot chemistry or does it have a shelf life? Is the sizing usually just brushed on or is it immersed in the solution, if so for how long?
    I found other sizings listed that were tested by the JAIC... "arrowroot, 1.4% (w/v); gelatin, 0.66% (w/v); gum arabic, 15% (v/v)". Does the w/v indicate grams per 100 ml.?
    Actually the entire document is a good read with some detailed test results if you have not seen it:
    http://aic.stanford.edu/jaic/article...-01-002_3.html
    The link is for the page that relates to my questions..... Surprisingly, I noticed they are using gelatine with no inhibiting reactions just a little reduction in contrast.... Who knew.... (I guess Kerik did)!!
    Thanks in advance...

  2. #2

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    Annie, is not a sizing per se, but a pre bath. You immerse the entire sheet in the solution or you can just skim the sheet over the solution, depending on the paper.

    I use a 2% solution by weight, 2 grams in 100 ml of water, I think Clay uses a 1% solution, do some testing and see what is best for your paper.

    I save the oxalic acid solution, but if you dont use it often enough it starts to grow mold, so essentially I would say it is a one shot deal.

    As before, you will have to do some testing and determine how long you have to immerse the paper, I usually do 5 minutes, but Socorro has a lot of alkaline sizing, I can even smell the stuff after I am done.

    Good luck and have fun.

  3. #3

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    Annie,

    The oxalic acid is not for sizing it is a prep treatment to remove excessive buffering in the paper, which can cause problems with tone smoothness in pt/pd.

    This may actually hurt the sizing in some papers, but most that we use for pt/pd won't be affected by the oxalic.

    There aren't any hard and fast rules on this. Some papers (like Platine) may benefit from a 1% solution brushed on. Other papers (like Fabrianno Uno, or the new Extra White) need to be soaked in a 1 to 2% solution for a few minutes. They will actually fizz and bubble as the carbonate reacts with the acid to produce CO2. I leave them in until the fizzing is gone, and then a little longer to be sure.

    There aren't any hard and fast rules on this (did I just say that?). Do it by volume, otherwise, you'll have a fairly strong solution. I use it one shot, because the ox is cheap enough that it doesn't make sense to try to keep it in solution. It may also pick up enough contaminants that you wouldn't want to reuse it again anyway.

    Probably the easiest sizing material is gelatine, because you can get it at the store. But you will need a way to harden it. Some people use glyoxol, others use formaldahyde, chrome alum, and other things.

    What paper are you planning to use this on? That may help determine what would be the best approach.

    FWIW, my attitude is to not make the solution any more complicated than it needs to be. If you don't need to precoat or size, then don't do it, because you risk complicating and compromising the results through other interactions that don't exist without the step. (for example, uneven sizing can cause blotchiness, heavy sizing can result in washoff problems, etc.).


    ---Michael

  4. #4

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    I have on order some Cot 320 and Arches Platine..... I have on hand some Fabriano which is the one I thought required the pre-soak. I also have some Arches Electric with the lightening bolt watermark but I cannot find any information on that paper so I am putting it aside for now.

    Thanks!

  5. #5

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    Annie,

    If you have Fabrianno Uno, you will probably be somewhat disappointed with the results, unless you are thinking of a print with high key tonality. It has a quite low dmax, which can be described at best as 'gray'.

    If you have the new Artistico Extra White, it appears to be a much better pt/pd paper than the old Uno it replaces. I haven't done any real printing on it yet (other than gum-overs) but it appears that it will make a good forceful pt/pd print if you wish.

    I misspoke in my last post. I recommend doing it by weight/volume, and use about 2% or so. If you use warm water (but not real hot) the water will penetrate faster, and neutralize the paper faster. Too hot, and you will damage the sizing, which will make the paper soak up the coating solution like crazy.

    There are plenty of other Fabrianno papers, but I don't know much about the others.

    The Platine and COT320 are very similar to each other, and in my opinion don't require the precoat. However, I think they may look better with a precoat if you do a single sentizer coat, rather than double coat.

    Arches Electric? I'm not familiar with that one. I love the watermarks that they use in these papers. The old Uno had a wonderful stylized cross.


    ---Michael

  6. #6

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    Michael,

    Thanks for the additional information.

    I think Arches Electric may be a vintage paper ... the watermark looks Deco/Flash Gordon with the lightening bolts radiating from the name, the mark is about 6" in diameter

    Annie

  7. #7
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    Hey Annie:

    Oxalic is not really a sizing agent as much as a buffer neutralizer for papers. Pt/Pd is an acidic process, and the trend toward archival (i.e. pH+) papers means that paper makers now incorporate significant amounts of carbonate buffer in their papers to create a non-acidic paper that doesn't age (thus yellow) as quickly. Unfortunately these same buffers are inimical to the pt/pd sensitizer blend (pH around 3 if memory serves) and give weak, anemic prints unless the buffer is neutralized in this oxalic acid solution prior to coating. This treatment makes many papers that absolutely suck as pt/pd papers as delivered actually work quite well after treatment in an oxalic acid bath. A great example is the new Fabriano Extra White. Coat it straight out of the package and you have a really lousy print. Soak it in 1% oxalic acid for five minutes, dry and then coat it and the paper really looks great.

    Sizing, on the other hand, is actually a way of filling the pore space of the paper with a filler - either starch or gelatin - to give the paper more body and make it less absorbent. Most of us size papers that we intend to use for gum layers to prevent the gum from staining our highlight areas.

    Most good pt/pd papers have enough internal sizing that it would be redundant to size them again. On the other hand, if you wanted to print on some unusual paper like newsprint, both sizing and oxalic would probably be necessary to get a decent print.

    Hope this helps.

  8. #8

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    Clay,

    Newsprint is normally quite acidic, so you probably wouldn't need to treat it with oxalic before you print, but you will need to size it heavily.

    Annie,

    In the US, you can get a pen from Light Impressions called the pH Pen, which effectively indicates the pH balance of the paper with a swipe of the pen. In most cases, a paper that is acidic (yellow) with the pen won't benefit from the pretreatment, but the basic (blue) papers will benefit. You can also see the blue stripe turn yellow in the treatment, so you know the balance has shifted.

    If you settle on one or two papers, you don't need the pen, but when experimenting with new papers, it might come in handy to help you determine what the general character of the paper is before you begin trials.


    ---Michael

  9. #9

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    Mar 2003
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    Great, Thanks! I think I have the sizing thing straightened out.

    I am trying to be prudent with my printing and find one traditional paper to work with for now as I am moving up to the larger negatives...... Plus I wish to get some decent prints so I can attend that Platinum Puddlejump this summer.



 

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