Pigment suitability for gum printing

Tor-Einar Jarnbjo · Apr 28, 2017

I have been doing some gum printing using tube colours from Winsor & Newton. Even if the prints turn out quite good, I always have problems obtaining a decent density. I know that it is common to print several layers on top of eachother, but to save time (which I don't have too much of), I have also considered different options to get a better coverage/density with only one layer.

One thing I have always wondered about, but not seen discussed anywhere, is that when using tube colours, is that the paint itself is dilluted quite a bit with gum and dichromate solution. It is often recommended to use a ratio of only one part paint to 10-20 parts of gum/dichromate mixture. This will of course limit the amount of colour being applicable with each layer.

I was therefore considering trying to use powder pigments instead to increase the density of each layer. Powder pigments are usually marked as suitable for different techniques (e.g. water paint, oil paint, acrylic paint, tempera and so on) and I was basically wondering if the pigments I choose need to be suitable for water colours, or if I can also try e.g. oil paint pigments?

chrisaisenbrey · Apr 28, 2017

Well pigments have a more or less hydrophobic surface and it will be more or less difficult to distribute the pigments in water or oil. In most cases you can’t just add the pigments, but you have to use a glass muller and add some wetting agents.

Dyes are soluble in water, but I guess they are not usefully for gum print since they will simply wash out.

For carbon print I use isopropanol as wetting agent. The standard black pigment is of cause lamp black/ carbon black. (Leading to the English designation for carbon print)

A good source for pigments and information on them is:

http://www.kremer-pigmente.com

Tor-Einar Jarnbjo · Apr 28, 2017

chrisaisenbrey said:
Well pigments have a more or less hydrophobic surface and it will be more or less difficult to distribute the pigments in water or oil. In most cases you can’t just add the pigments, but you have to use a glass muller and add some wetting agents.

But couldn't a pigment with a hydrophobic surface still be easily mixed in a gum solution due to the high viscosity?

Funny that you suggest Kremer Pigmente. I visited a Kremer shop just a while ago, but the sales person was not sure which pigments to recommend for a gum/dichromate base.

Bob Carnie · Apr 28, 2017

I use Windsor Newton and Daniel Smith.. I mainly use transparent , but in some cases opaque.

I always do multiple layers to build up density and contrast, It is the nature of the beast that a single shot will look somewhat weak.
I have not tried increasing the pigment load within the gum to a point that maybe could be done, when I started I was getting a lot of problems
with fisheyes and it turned out that I was not mixing the pigment , pigment gum dicromate, enough .

I will be curious to see what kind of single print densitys you can get and encourage you to post some here. If you look in my media page you can
see that most of the work I posted is either gum over palladium or duotone gum.

to date I have not made a single shot gum to my satisfaction.

chrisaisenbrey · Apr 28, 2017

Tor-Einar Jarnbjo said:
But couldn't a pigment with a hydrophobic surface still be easily mixed in a gum solution due to the high viscosity?

Funny that you suggest Kremer Pigmente. I visited a Kremer shop just a while ago, but the sales person was not sure which pigments to recommend for a gum/dichromate base.

Probably the person didn’t know about gum printing, but he should have told you that water color is normally made with gum arabicum. So, any pigment recommended for water color should be fine for gum print.
But still it might be some work to distribute the pigments evenly, especially with hydrophobic pigments. Viscosity helps of cause. There are descriptions for making water-colors with gum arabicum and pigments in the web.

Tor-Einar Jarnbjo · Apr 28, 2017

Bob Carnie, first of all, many thanks for all the great videos on alternative processes you have published on Youtube!

I have already done some tests with a higher ratio of paint vs gum/bichromate or painting several layers before exposing only once. That helps increasing the maximum density of the print, but I run into other problems. It gets difficult to clear all residue paint from the highlights and with each layer of paint, it gets more difficult to dry the paper completely flat. The issues I have with paper warp is perhaps more related to my improvised and mediocre printing frame, but I tend to experience blurry areas in the image, where I probably have air gaps between the paper and the negative. Depending on the motive, both slightly 'fogged' highlights and slightly blurred areas is not necessarily a problem, but it is of course difficult to get consistent prints and I currently have the impression, that it is just luck if I happen to get an acceptable print.

Here is one of the better prints I have managed to make (single layer, Windsor & Newton lamp black):

Tor-Einar Jarnbjo · Apr 28, 2017

chrisaisenbrey said:
Probably the person didn’t know about gum printing, but he should have told you that water color is normally made with gum arabicum. So, any pigment recommended for water color should be fine for gum print.

Yes, it is of course unlikely that even a sales person in a shop specializing in pigments have much knowledge about gum printing. His uncertainty was perhaps also more related to how the pigments would interact with dichromate and not which pigments to use for a 'plain' gum based paint. I was also looking for coloured pigments to try colour printing and it is not impossible that the compounds, on which colour pigments are based, for some reason or another would not cope well being mixed with a dichromate solution.

Bob Carnie · Apr 28, 2017

For colour printing I use a
blue green shade series 1 transparent
Magenta series 1 transparent
Yellow series 1 opaque- lay this one down first
or
Indian Yellow- series 1 transparent.

I also mix pigments in different ratios to effect the colour I want, a knowledge of colour theory as well a colour wheel is good to have in your workspace.

Gum can look abstract to surprisingly real life, it is an incredible method of making prints and much experimentation is needed.
Water control is very critical and much trial and error, never be afraid to mix combinations... Blue(green shade) followed by a deep red coating is very lovely.

I recommend good vacuum and a decent registration regimen if you want to expand beyond single coat gums.

From your sample I see what I expect with single coat, I have heard lamp black is difficult but I get results.

I use burnt ochre or raw ochre as my first coat with all portraits, followed by a strong colour.

chrisaisenbrey · Apr 28, 2017

Tor-Einar Jarnbjo said:
Yes, it is of course unlikely that even a sales person in a shop specializing in pigments have much knowledge about gum printing. His uncertainty was perhaps also more related to how the pigments would interact with dichromate and not which pigments to use for a 'plain' gum based paint. I was also looking for coloured pigments to try colour printing and it is not impossible that the compounds, on which colour pigments are based, for some reason or another would not cope well being mixed with a dichromate solution.

I would concentrate on organic pigments, since I think they are most “powerful” per weight.

I have no experience with dichromate since I use Diazo with carbon print, but I would not worry too much. Stable commercial pigments should be quite resistant to oxidation. But at the end you have to try it.

jerunder · Oct 30, 2018

Hey guys, this is fantastic info thank you. I have some old powder pigments left by my grandfather who was an artist, burnt ochre being one, but quite a few different ones too, prussian blue, cadmium yellow and vermillion among them. Wondering if to go with these and experiment with mixing them or buy quality tube watercolours... Your thoughts would be appreciated thank you

Peter Rockstroh01 · Oct 30, 2018

Pigments are relatively difficult to wet and disperse, and even more complicated to stabilize. A good pigment dispersion has nearly twenty ingredients,
of which a dozen are required to control viscosity, gloss, sedimentation and so forth. Inorganics (cadmium, chrome, ultramarine) are easier to disperse,
but have poor tinting strength. Organics have a very high tinting strength, but due to a very high specific surface, are difficult to wet and disperse with
domestic gear. Your best bet is buying industrial pigment dispersions from a paint factory nearby. BASF, Bayer, Clariant and many others produce
these (45% pigment content is the standard). They will save yoiu a lot of work and inconsistencies, and they are MUCH cheaper than anything bought
at an art store

Pigment suitability for gum printing

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