From: Peter Fredrik (pete@fotem.demon.co.uk)
Date: 05/09/01-07:55:52 PM Z
Dear Dave,
Dave Rose wrote:
> Hello Katherine,
>
> Could you recommend suitable pigments to achieve "brilliant and saturated"
> results?
>
> So far I've experimented with: Cyanotype, Phtalo Blue, Cadmium Yellow,
> Quinicridone Red, and Alizarin Crimson. Printing test 4x5 negatives (photo
> of a gray card and color chart), I've been able to get good color balance,
> but the color is anything but brilliant. I'd love to get Cibachrome
> intensity in a 3-color gum print.
I operate a similar system to gum /bichro using whole egg as an emulsion and
have for the past few years managed to achieve highly saturated coloration in
my prints . In formulating this process the following
pigments have been most helpful in obtaining strong saturated colour
.Cyan = Phalocyanine Blue (ASTM PB15) has a lot of names Windsor, Monstral blue
etc. and comes as previously stated in a green or red shade. I use the red
shade most of the time. This is an easy colour to use, but it does have a high
tinting strength , and therefore liable to stain.
Magenta = Acra Violet (Quinicridone Magenta ASTM PR 122) will need more coats
to reach the same colour value as the phalocyanine blue
Yellow = Hansa Yellow Medium (Arylide Yellow ASTM PY 73) a nice transparent
pigment
I have found however that the problem of dull colour does not lie with the
pigment, but considerations
which are primarily to do with
1) pigment stain
2) dichromate stain
Most pigments don't stain but the water-colour paper does ! in fact it is made
for that express purpose Water-colour paper is made to work for water-colour
painting not gum / PVA/egg printmaking .The function of the water-colour paint
is to stain the paper. It has to go into the surface and get attached to the
paper fibres and not come out. With sensitive sizing and precise balancing of
the gum and the pigment mix a skilled gum printer can travel along a razor edge
of technique whereby the pigment emulsion can go into the paper and come out
leaving no pigment behind to adulterate the image. It is hard work a true
labour of love , and the gum printers that achieve this control in multicolour
work have my sincere admiration.
I have dealt with this topic in a previos thread. So I will just repeart my
findings --:
>From an e;mail I sent to the list in regard to dichromate stain
>
> So do I
> .
> Okay let me try to explain .
>
> I have been for years concerned with trying to obtain maximum colour
> saturation
> in photo-alt at the same time as achieving creative flexibility.
>
> When I first started the brown stain proved a problem degrading the cyan to
> a
> muddy grey knocking the edge of the magenta and affecting the yellow only to
> a
> slight extent .
>
> This problem was quickly solved by using any of the following clearing
> procedure's
> 5% sol bath of either
> sodium sulphite , sod/pot metabisulphite, pot alum, liquid acid hardener, or
> a
> long soak wash in running water 12 hrs /24 hrs, all of these baths gave much
> cleaner colour the most noticeable was the effect on the cyan which went from
> a
> muddy grey to a fully saturated blue, so far so good.
>
> However I noticed as time went there seemed to a slight green cast appearing
> which
> was a will of the wisp effect hard to predict .At first I thought it was
> badly
> mixed pigment . I was using acrylic colour so I did a series of tests without
> any
> colloid present and mixed them physically with a paint brush ,the result no
> green
> caste. So it had to be the colloid /bichro mix .Working on this surmise I did
> a
> further series of tests with out pigment the results of which were most
> interesting .With a full exposure the colloid went brown using different
> papers
> the shade of brown was different, I also used three different colloid to
> cross
> check on a control sheet of fabriano artistico
> 1) W&New gum , 2) egg,, 3) gloy gave the following results --: 1) strong
> brown 2) green brown 3) medium brown
>
> These tests were then subjected to the clearing baths and as expected they
> each
> turned a soft green grey .The colour of turquoise that has been let down
> with a
> slight grey tone. So how could I get rid of this residual stain a number of
> other
> chemicals were tried with no effect.
>
> Then I remembered work I had done on bromoil year's before many bromoil
> bleaches
> contain a small amount of sulphuric acid, which had the effect of turning the
>
> gelatine colourless before inking, and as similar chemistry is employed I
> decided
> to give it a try.
>
> BINGO it worked the brown stain disappeared and no green stain reappeared,
> however
> the stain did not in fact go away on heavy exposure a light neutral grey tone
> was
> created, but this did not pose any problems as it just made the colours in
> the
> shadow regions slightly darker and in effect undetectable, in normal
> practise.
>
> So there we are,
>
> All my best,
>
> Pete.
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