Stock paint: gum solutions

[Katharine Thayer <kthayer@pacifier.com>]

Loris, I mix my stock mixes by eye rather than by quantity, but just  
eyeballing your amounts I'd  agree with Marek that your paint/gum  
ratios seem on the high side for tricolor. Since the PY 151 is a weak  
pigment, it's possible 1:2 might not be too far off,   though I've  
not used PY 151 beyond an initial test because it's just too light a  
yellow for my taste.  My ratios for PV 19 and thalo are somewhere  
between yours and Marek's.

While I would agree with the ranking of amounts for these three  
pigments (most for PY151, middling for PV19, and least for thalo) you  
would never find me making general statements about relative amounts  
of "yellow" "magenta" and "cyan" because pigment strengths don't  
cluster in hue ranges that way, in other words yellow pigments aren't  
generally weaker than magenta pigments aren't generally weaker than  
cyan pigments; they vary all over the place.  For different pigment  
combinations, it could go in  different orders.

As Bruce McEvoy describes so competently on that page (which I hadn't  
found my way to before-- what a wonderful site; there are layers and  
layers of information to discover) there's a wide variability between  
pigments and even between brands of pigments as to how much pigment  
is required to achieve an optimum luminosity/color saturation, and  
that's why I mix by eye rather than by measuring.  I check that the  
gum/pigment mix is at optimal color saturation for that particular  
pigment by brushing it on a scrap of paper and comparing to standard  
swatches that I keep.   Depending on the pigment and the use I have  
in mind, that can be as little as a squeeze of the tube (say for  
thalo or lamp black) in 20-25 cc gum and as much as a whole tube in  
15 ml gum, to make a very dark black with PBk11.  Then I either use  
that mix as it is or dilute it, depending on the purpose I have in  
mind.  For example, for very subtle smooth tonal gradations in  
highlights and midtones (I'm thinking monochrome here more than  
tricolor)  I dilute it more (and then usually add another printing  
with a more concentrated mix for the shadows, unless my goal is a  
very high-key print) than I would for either a one-coat gum or for  
tricolor.  So I use many different pigment concentrations for  
different purposes.

I don't find it necessary to print more than three layers to achieve  
a full tonal scale in tricolor, but I also think that printing with  
more layers of a lighter pigment mix gives a lovely delicate effect,  
so it really depends on the image and what you want to do with it.

Katharine



Loris wrote:
> I was reading handprint.com's "The Secret of Glowing Color" page,  
> which
> contains very good and interesting information, especially in the  
> section
> "Not Black, Not Light".
> (http://www.handprint.com/HP/WCL/tech16.html)
>
> I slowly feel the need of making stock paint:gum solutions, in  
> order to
> get more consistency and ease of use. Mixing small amounts of  
> paint:gum
> solutions is hard to do consistently, especially with strong  
> colorants and
> small image sizes. (Because squeezing small amnt. from the tube is not
> easy!)
>
> I decided to make stock solutions as listed below:
>
> Yellow  PY151  1:2 (1:4 final) -> 15ml paint + 30ml gum
> Magenta PV19   1:3 (1:6 final) -> 15ml paint + 45ml gum
> Cyan    PB15:3 1:4 (1:8 final) -> 15ml paint + 60ml gum
>
> Since the stock paint:gum is further diluted 1:1 with dichromate, the
> actual paint dilution in the coating solution will be exactly the  
> half of
> what it is in the paint:gum solution. (See inside parenthesis.)
>
> This question goes to users of stock paint:gum solutions (such as
> Katharine and Christina):
>
> Do you find above figures close to ideal? What is your experience with
> those pigments? Anything to pay attention / be careful about using
> paint:gum stock solutions?
>
> Thanks in advance,
> Loris.