RE: (1) Gum over Cyanotype on sized Masa paper (rough side) - (2)Pigment that makes gum insoluble w/o exposure?
I started to print on the rough side (cyanotype) and then switched to the smooth side with good results (cyanotype again) and remained there. I hever thought to go back to the rough side - I'm grateful to Rayul for reminding me the rough side. Since I have reverted, I had no flaking issues. See my last gum over cyanotype print on sized Masa (rough side) below: Full image (actual size 17 x 27cm, 6 5/8 x 10 5/8"): http://www.loris.medici.name/gum/gum_over_cyano_02_sm.jpg Detail (actual size 4.5 x 5cm, 1 6/8 x2"): http://www.loris.medici.name/gum/gum_over_cyano_02_crop.jpg Diagram: http://www.loris.medici.name/gum/gum_over_cyano_02_diagram.jpg Image on unsized Masa (rough side): http://www.loris.medici.name/gum/gum_over_cyanotype_01_sm.jpg As you can see the result is much much better despite it's hard to make a direct comparison since: a) I have used transparent pigments (hoping to get less muddy results) b) I have used 1:1 diluted 2A:1B traditional cyanotype (because undiluted is too dark for making gum overcoats I thought) In the second print (on sized paper). In any case, the difference in whites is obvious. Sizing and using the back side is the key to success with this paper... As you notice, I'm trying primary (or quasi primary) colors with this print, because I also aim to learn how different primaries interact. Will try to use darker and/or more opaque paints (or more pigment with the same paints) in the next try since I was expecting a more neutral final image color... About red: Mine is "gamma quinacridone" (according to: http://www.handprint.com/HP/WCL/waterc.html#PV19R). It's a very strong pigment, I succeeded by cutting the pigment amnt. and exposure time considerably. Layer info: 1. 1:1 diluted 2A:1B traditional cyanotype, 4:00 2. Schmincke Cadmium Yellow Light 224 (PY35), pigment load: light, 4:00 3. Schmincke Ruby Red 351 (PV19), pigment load: very light, 1:45 (All layers with the same negative calibrated for 2A:1B traditional cyanotype.) BTW, the creasing you see was caused by me being clumsy while affixing the paper to Yupo. I would normally discard the paper and re-make but I thought it suits the subject matter and pursued. The effect is not that strong, it's exaggerated by the scanner -> you can't see it unless you look the image in strong and very oblique light... Regards, Loris. -----Original Message----- From: Christina Z. Anderson [mailto:zphoto@montana.net] Sent: Monday, September 24, 2007 5:52 PM To: alt-photo-process-l@usask.ca Subject: 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
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