Re: gum prints on Yupo
Silica fume looks good. Thanks for the tip. I'll try that when I run our of pumice. I found two large jars of animal glue dry gesso mix on the sale table of a craft store , and bought both of them for $10 http://www.pearlpaint.com/shop~parentID~9915~categoryID~9909.htm Bad. On first attempt, the gesso slid right off the surface as soon as I brushed on gum emulsion. Added gluteraldahyde and it stuck to plywood (still won't stick to aluminum), but it stains horribly. 2008/11/4 Loris Medici <mail@loris.medici.name>: > Hi Keith, > > I have two different kinds of gesso. Both Daler Rowney brand, one System-3 > white, the other is Cyrla black. System-3 white works well in terms of > keeping the gum image (but still exhibit a chemical - not pigment! - > general stain). Cyrla black reacts just as you describe and doesn't hold > the gum image (even with added calcium carbonate) at all; as soon as you > put the image in the development water, it leaves the substrate instantly > (exactly as you experienced / showed in your first trial with Artboards > gesso). > > I plan to change the gesso additive from calcium carbonate to silica fume > -> hoping it won't react with dichromate but still provide tooth for gum > emulsion... Better, I will look for proper flexible plaster -> for making > "gum-o-fresco"s ;) > > Your gesso tests are beatiful / interesting! I liked most the last one... > > Regards, > Loris. > > > 3 Kasım 2008, Pazartesi, 7:26 pm tarihinde, Keith Gerling yazmış: >> Loris, >> >> I have experienced a definite pigment stain with that kind of size - >> an odd "solarized" look where the highlights stained and the midtones >> would clear. A coat of hardened gelatin seemed to help. I wonder if >> you observe the same effect as I do using a similar mix: when I brush >> on the emulsion, I detect a very obvious separation where the surface >> draws the dichromate away from the pigment. Initial brushstrokes are >> very clearly orange and only with repeated brushing does the emulsion >> seem to "come together". In my case the exposures are much longer, >> but that may be due to the fact that I am using lampblack and it is >> self masking. In any event, my normal exposure with 1 part gum to 1 >> part saturated pot di is 8 minutes, and I'm having to use 20. >> >> Keith >> >> 2008/11/3 Loris Medici <mail@loris.medici.name>: >>> I had encouraging results printing on yupo coated with acrylic gesso + >>> calcium carbonate mixture. I just did two tests, one 8 minutes, the >>> other >>> 4 minutes exposure. Both were highly overexposed (even a foam brush >>> wont >>> clear darkest part of the image). Will try 02:00, 01:00 and 0:30 >>> exposures >>> and then share the results... Coating is easy as long as you brush >>> presistently for a long time (emulsion doesn't bead much) and you keep >>> the >>> emulsion very thin (if not, flaking occurs). >>> >>> One important problem is: the base gets stained (not pigment, some kind >>> of >>> chemical stain), and doesn't seem to clear with sodium metabisulfite. >>> Will >>> see how it goes with shorter exposures. If it continues to stay so then >>> I >>> won't be able to get pure white -> only ecru / warm background. Not a >>> problem for some images, big one for others... >>> >>> The base coating consists of: >>> 1 part acrylic gesso >>> 1 part calcium carbonate powder >>> 1/2 part water (all by weight) >>> mixed homogenously giving a creamy consistency. Applied with a foam >>> brush, >>> smoothed gently with a watercolor wash brush. >>> >>> I must admit it's not much interesting for Yupo. But if I manage to >>> make >>> it work, it can be used as a nice way to print on rigid / impermeable >>> and >>> smooth substrates such as aluminum sheets or MDF, HDF or plywood... >>> >>> More later, >>> Loris. >>> >>> >>> 2 Kasım 2008, Pazar, 5:43 pm tarihinde, Marek Matusz yazmış: >>>> >>>> Erie, >>>> If you look closely at the pictures that I posted you can see the >>>> "imperfections" in the print, but these are best prints on Yupo that I >>>> kept. Gelatin sizing was a total disaster with the gum layer not >>>> sticking >>>> to it at all. >>>> >>>> What worked best for me is no treatment to the sufrace at all. Very >>>> thin >>>> gum layer (means dilute gum solution) rolled with a gum roller gives >>>> decent results. It seems that the thinner the gum the better the >>>> results. >>>> My exposures got very short as well, around 30 seconds. I wonder if >>>> scrubbing the paper with cleaning powder would help a bit? > >
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