From: Mary Pat McNally (mcnally@psfc.mit.edu)
Date: 03/18/03-09:39:58 AM Z
I was taught that staining has a great deal to do with the way the
paper is sized. Some pigments are more likely to stain than others.
When I initially began doing gums I had a great deal of trouble with
staining but I experimented with sizing and I haven't had trouble
with staining. Mary Pat McNally
>I completely agree that there are "too many variables to come up with a
>definitive answer to stain". That's why I have a real problem with
>individuals using "one little test" in an attempt to prove or disprove
>theories on staining. If we're going to have an intelligent discussion on
>staining, let's differentiate between quinacridone violet and burnt sienna.
>Put aside all other variables, the pigments themselves make a huge
>difference in the results achieved.
>
>Your comments on relative humidity are especially interesting. For whatever
>reason (much lower humidity and/or higher PH water?), my gum exposures are
>noticeably longer here in Wyoming than those made in New Jersey - with all
>other variables being the same.
>
>Best regards,
>Cactus Cowboy
>Big Wonderful Wyoming
>
>----- Original Message -----
>From: "Christina Z. Anderson" <zphoto@montana.net>
>To: "Alt Photo List" <alt-photo-process-l@sask.usask.ca>
>Sent: Monday, March 17, 2003 9:50 AM
>Subject: Gum printing, staining, pigment stain
>
>
>> For you Gum Printers out there, here's some thoughts:
>> I keep mulling on the staining factor. I think there are too many
>> variables to come up with a definitive answer to stain, which is what has
>> created problems in the past on this list--in essence, not allowing people
>> to believe in their own variables, which are all true. I think we can all
>> agree that there is not one factor that causes stain. I think we *should*
>> all agree that we can pool all our answers together as *equally* valid and
>> come up with a whole that is much worthier than the part answers.
>> Demachy back in 1898 said stain was caused by using too little gum.
>In
>> essence, the gum keeps the pigment suspended above the paper so it doesn't
>> have a chance to sink into the fibers. This is true, too, of
>> watercolorists, who use gum arabic to allow lift off of paint.
>> Demachy also said that too much sensitizer in the mix dilutes it to
>an
>> undesirable consistency so that it is able to sink in, causing staining.
>> In 1905 in The Modern Way of Picture Making he says that staining is
>> caused by too much liquid, bichromate, or water in the sensitive mixture.
>> If the staining in the highlights is *granular* that is too much pigment.
>I
>> got both in the Z process, but in deference to Z, I was using one of the
>> most staining pigments, quinacridone violet.
>> Why I began attempting the Livick process of such a high
>concentration
>> of pigment to gum (6/12) is that I have been able to prove to myself (no
>one
>> else, mind you!) that you can use a heck of a lot of pigment before you
>get
>> stain with some colors, even on unsized paper. With QV, a highly staining
>> color, I will now dilute my 6/12 mix in half, so I *do* think there is a
>> correlation between so called staining watercolors and gum stain, insofar
>as
>> with the staining pigments you have to use more gum. Said another way, a
>> lower pigment to gum ratio. Which is why the testing of plain gum and
>> pigment will give you some indication of a paint's staining power in
>certain
>> gum dilutions; then take that further and test the same with the
>dichromate
>> and exposure variables that Judy proposes. Or, throw caution to the wind
>> and just assume that you need less of the staining pigments (carmine, lamp
>> black, perinone orange, permanent red, perylene Maroon, thalos, q violet,
>> etc.). Luckily the staining colors are intense enough that a little goes
>a
>> long way. But staining pigments will stain if not enough gum is used, or
>if
>> too much dichromate dilutes the solution so the paint particles hit the
>> paper and sink in.
>> Furthermore, Hilary Page says:
>> p 10-11 ox gall is a surfactant added to some paints that enables the
>paint
>> to sink deeply into the paper. Some do not put this in their paints.
>And,
>> "In watercolors the vehicle formulation, as well as pigment type and
>> particle size, are factors in predicting whether a paint will lift off of
>or
>> stain your watercolor paper. Mediums lift more as they contain more gum
>> arabic and they stain more as they contain more glycerine." Further,
>> "toners (added to the tube) are organic pigments based on a metallic
>> salt...adding toners to a color can make the color appear brighter, but
>they
>> also cause them to stain your brush, water container, paper, to bleed..."
>I
>> should've realized this when my plastic *teaspoons* were stained with
>> quinacridone violet! :)
>> Further, Look at the list below of other possible stain causes:
>> Sizing--initial of paper brand, then your added sizing.
>> Number of coats you do.
>> Absorbency of paper, type of paper.
>> Gum brand.
>> Exposure.
>> Dichromate used--I happen to observe more staining with pot di,
>contrary
>> to the usual adage about am di.
>> Dark reaction and continuing action.
>> Acidity of gum.
>> Humidity of your sensitizer (both acidity and humidity according to
>> Kosar affect exposure, and I think deserve a closer look if someone wants
>to
>> do some testing with me of ammonia and lemon juice side by side added to
>> sensitizer or coated on the paper and dried. AND exposing wet paper.
>Kosar
>> says p. 81 that humidity is necessary in the sensitizer upon exposure to
>> hasten hardening, and I quote: "when the humidity is high, the
>sensitivity
>> to light is also high, the speed of light hardening being almost double
>with
>> an increase of 30 percent in RH..doesn't this fly in the face of the usual
>> theory that it is not light sensitive when wet?? How wet is the deal I
>> guess--dry to the touch but with some moisture suspended in the
>sensitizer,
>> I would assume).
>> Staining vs. non staining colors.
>> Medium your pigment comes in.
>> Grind of pigment.
>> Etc. Etc.
>> You see?
>> In regards to below, Judy, I think it may be backwards from what you
>> say. Most of the staining colors are the new synthetic organics--thalos,
>> quinacridones, vat pigments, dioxazines, pyrroles. They are small
>> particled. The quinacridones are favored by the auto industry because
>they
>> have small particle sizes. Not developed commercially until 1958 (p. 80
>> Page).
>> Enough of my rambling.
>> Chris
>>
>> <Judy says>
>> christina... strangely or not, the "staining" category doesn't apply to
>> gum printing, or not that I've ever been able to detect.
>>
>> I'd already noticed lack of connection with the manufacturer's designation
>> in my own printing -- I've found that *staining* when it happens is
>> due to some dumb mistake -- old emulsion, too hot, too humid, bad paper,
>> bad size -- or like that. But the explanation from the W-N lady of those
>> categories in *watercolor painting* was as I recall that the stainers are
>> colors made from the old mineral pigments. The particles are fairly large
>> and irregular & roll around and get stuck in the paper fibers. The
>> non-staining are the new synthetic colors with much finer particles,
>> "almost like dye."
>> But we don't get a lot of correlation of gum behavior with watercolor
>> behavior (that was the false premise of Scopick's "medium" for dry
>> pigment). In watercolor, the paint is thinned I mean really *thinned* with
>> water until it's just the palest tint.... and the gum arabic in those
>> veils and washes is almost non existent. In gum printing, even in the
>> zimmerman process, a much more robust paint-gum mix is used. The half
>> tones and highlights are achieved by removing the unhardened part, not by
>> thinning the paint with water. So even with little or no gum added as in
>> Zimmerman, the pigment remains embedded in gum.
>>
>>
>>
>>
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