Re: (1) Gum over Cyanotype on sized Masa paper (rough side) - (2)Pigment that makes gum insoluble w/o exposure?
Loris, I'm so glad you experimented with MASA as per Rajul's advice--makes me want to try it now that two of you have found it to be suitable. I have never had a pigment insolubilize gum, but after reading Marek's question with the one pigment and carbon it makes me wonder something. A bit ago I had mentioned the fact that formaldehyde hardens gelatin but not gum and that is why it can be used as a preservative in gum solutions. I wonder, therefore, if carbon is more sensitive to this kind of happening than gum is, and if some of these feelings of spontaneous hardening were a holdover from carbon, and gum being associated with carbon as a "direct carbon" process as it was first called. I was explained the difference between the two--chemists please correct me but gum is composed of carboxyl (sp?) groups and gelatin of amino acid chains? So that might explain some differences in results between the two substances--they are colloids but not the same colloid. The very FIRST mention of spontaneous insolubilization was 1894!! In the very first gum book ever written!! Rouille Ladeveze. Blanc d'argent. If anyone in France can locate me some blanc d'argent I'd love to test it. So even though I say I have never seen this I cannot say that it doesn't happen. Anyway, on to red. I have never had a red spontaneously harden, but I have found that students will tend to confuse two things--stain and overexposure. I have no idea if either of these are your case. Two, is the ruby red a blue red? Offlist I got a question from Michael Koch-Schulte about whether I had found reds to be faster than other colors and no I had not, but I did determine a difference in exposure between a blue red and an orange red. In fact, if I am not careful to expose the orange red much longer (certain ones, btw) it'll all whoosh off. These are with pretty dense layers, like the color of the layer looks as colored as the pigment itself. It would be instructive for us to share what we have all found related to exposure times of different colors. Old literature says blue is the fastest exposing and I have certainly found that to be true, and yellow slowest, but then I wonder if the difference of exposure times is directly related to the amount of pigment one uses and that will explain the variations we are all finding--for instance, if I am just using a little pigment in my mix of any color, maybe there is not much of a difference in exposure between all colors, but if I am using a LOT of any color with supersaturated layers, that's when the noticeable difference in exposure time crops up. And I am not just talking the darkness of the pigment affecting exposure time (e.g. black is the darkest, or saturated thalo blue as compared to saturated yellow, for instance). I'm talking actual colors acting as filters to the light--and as I said in my Magnachrom article, it stands to reason that yellow would be slow by filtering out UV light the best. And this would also be a possible explanation to why an orange red biased to yellow prints slower than a blue-red biased toward a faster color. Because there are so many variables that gummists use to make their prints (amount of pigment, thickness of layer, whatnot) there probably is no way we could build up an agreement about any of this, and I expect 20 emails shortly refuting anything I have said here, but suffice it to say I have never had any red insolubilize gum but I sure have seen overexposure with it that gives pretty red squares of image :). Chris Thanks Rayul. I tried the rough side (sized) and it works like a charm - very clean whites. Since I started to print on the smooth size, I was forcing that -> never thought to go back to the rough side. Both Cyanotype and gum are sharp and nice on the rough side - when sized. I also established a protocol in which I don't experience much registration problems... Actually I was planning to post the result but I ruined the print in the last (Schmincke Ruby Red - single pigment; Quinacridone Red PV19) layer -> the paint doesn't like to dissolve much - grrrr. Are there watercolor paints (in tubes) that make gum insoluble without exposure? (I know this is possible with gelatin / carbon printing...) Regards, Loris. -----Original Message----- From: Rajul [mailto:eyeear@telus.net] Sent: Saturday, September 22, 2007 6:29 PM To: alt-photo-process-l@usask.ca Subject: Re: Gum over Cyanotype on unsized Masa Paper I have consistently printed on the rough side. I do not regret the choice. I will do a sxs to compare how multiple passes print on the 2 sides. Rajul On 22-Sep-07, at 4:43 AM, Loris Medici wrote:Thanks Rajul. I already sized paper in ordinary manner (applying the sizing with a brush). Will try this on the next batch. Will to the comparison and share here. Quoting Rajul <eyeear@telus.net>:Loris, if you do size, it helps to wet the dried print, drain it to dampness, then pour and spread the hardened gelatin. It will be good to see sized sxs with unsized. Rajul On 21-Sep-07, at 3:44 PM, Loris Medici wrote:Wanted to share: http://www.loris.medici.name/gum/gum_over_cyanotype_01_sm.jpg It's a little bit muddy; will try on sized paper later (but I'm afraid since I experienced flaking back when I was testing sized Masa). Regards, Loris.
|
