Jarred...Virtually since the beginning of papermaking various sizings and coatings have been utilized to impart papers with variations in surface structure. Classic coatings and sizings are many... proteinaceous materials (gelatins & glues), starches, carboxymethyl cellulose, gums, waxes, clays, casein, kaolin, lime, baryta (blanc fixe) etc. etc. employed singly or in combination. In the last century many synthetic sizings and coating application techniques have been developed that have greatly increased the variation of papers and surfaces available. Polyacrylamide gels and resins are among these synthetic sizings.
What they have to do with Alt processing may turn out to be indeed nothing...
I am just investigating them because I am seeking a very specific surface for my Pt/Pd printing that is not available in the usual papers. I am trying to achieve a lustrous smooth surface that has a greater luminosity and will carry delicate detail.
Jorge... indeed most of the synthetic acrylic coatings that printers are now using will indeedyellow.. the polyacrylamides have been used in papermaking by Kodak for a while now (raw paper not in the coating) ... at least it is listed in the patents and the papers do not seem to be yellowing.... mind you the amounts are comparatively small. I have some gel crystals here now and they are not yellow.
PE... any thoughts on this?
Yikes... PE.. I see I am writing while you were posting....... anyway if I get any results that could be of benefit to anyone I shall post here... Cheers Annie
Annie, the polymers used in papers often are often accompanied by strong antioxidants to prevent yellowing. These are called 'free radical chain stoppers'. They are often covered in a separate patent claiming just their antioxidant properties in papers and may not show up in the polymer patents.
Therefore, the plain polymer may or may not yellow.
I have coated a lot of these, both hardenable and non-hardenable and they all have good and bad points. One of the hardest ones to deal with is the fact that they don't chill set. Coating on a machine is therefore difficult, but when hand coated, they can work out just fine. So something I would reject in a factory setup might be fine in a home darkroom.
That is why I said 'trial and error' because there is no rule or advice I could apply. I think that the only thing I could suggest is to try to keep the viscosity high for ease of coating. It would get too runny at low viscosity.
You can do this by getting a polymer with a high molecular weight (long chain length) or by making your polymer solution very concentrated before you coat (usually 10% or higher). You could also do this by spreading out a thin layer and allowing absorption of moisture to thicken up the layer.
Above all, it should not run when the coating is hanging to dry or lying down to dry or it will ruin the print, and that is my point about viscosity.
And, if the polymer will not harden, the print must be protected from moisture. Even contact with wet fingers will leave unsightly marks.
OTOH, some beatiful results might be obtained by the application of the right vehicle to the coating or as an overcoat.
You may want to try a carbowax 14xx or carbowax 3xxx series. These are clear stable polymers that dissolve in water and dry with a rather clear sheen.
I used to work at a plant that made polyacrylamide by the ton. It used as a water-treatment chemical. Eventually our company was purchased by ciba-geigy. We also made a bunch of water-soluble polymers used to size paper, such as poly-DMDAAC, and poly-acrylic acid which is used in diapers (those swell up beads)
If you are persistent you could find a distributer that would be willing to send you a sample.
The Blob That Ate Vancouver Island!!!
WOW... do these gel crystals love water... it is absolutely fascinating! I think it may be the resin I need.
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So you'll have RC pt/pd prints? Out of curiosity, have you tried coating a polyester base, like what is used for the Ilfochrome and Fuji supergloss materials?
Many printers use natural resins and gums as an overcoat so I guess RC/Pt has existed for a while... I am not aiming for 'supergloss' just trying to gain extra luster and luminosity without too much reflectance and glare ( I am making small handcrafted books at the moment so glare is an issue) thanks for the suggestions... Cheers!
Originally Posted by David A. Goldfarb
Either Ansel Adams or one of his contemporaries recommended using lithographers varnish to protect and add luster to matte surface prints. If I remember rightly the varnish was diluted with 4 or 5 parts of turpentine. The mixture was applied to the print with a cotton ball. As much of the varnish as possible was then removed using a lintfree cloth. A second or third application can be made to produce a shinier surface. I have prints that are 40 years old where I used this technique and it does add lusture and protection.
Annie, this is exactly one of their problems as well.
Originally Posted by Annie
After you coat them on your print, they will still 'love' water and may act unpredictably to changes in humidity. They certainly will tend to wash off or come off on damp fingers.
Water insoluable polymers such as a varnish from turps will not exhibit this property as noted here.
Coating on RC presents other problems, as the RC is either fixed out photo paper with a thick gel 'size' which is the residue from the photo emulsion, or is raw RC which must be sized with a thin gel pad or wash to promote adhesion. These two types of RC exhibit different coating and chemical properties. Both of these, in turn, exhibit different properties than FB papers. You cannot coat on unsized or unsubbed RC support. The coating will wash off during processing.
The main difference in these is that the FB paper acts as a large 'sink' for absorbing the chemistry you coat and the chemistry you coat is in intimate contact with the paper fibres and chemistry. In RC that was formerly photo paper, the 'sink' is intermediate and contains traces of chemsitry from its use as a photo paper. The RC that just has a thin size on it behaves more like a film support in that there is no 'sink' for chemistry and everything is on the surface. You can get tacky coatings and even crystal formation on this type of support.
PE...Having the emulsion engaged in intimate contact with the paper is essential ... for me having the image floating on an RC coating is not an acceptable proposal.
All I am really trying to do is bump the Dmax and gain some luminosity by adjusting the sizing in a paper that I have found to be wonderfully smooth with superior wet strength but with inconsistantcies in its absorption of the Pt emulsions and dry down... I am confident that eventually I will discover the 'sweet spot' for my paper. Thank you for your wonderful answers... I am learning much from you... Cheers Annie