U of S | Mailing List Archive | alt-photo-process-l | Re: gum prints on Yupo

Re: gum prints on Yupo

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

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...


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?