Advice for Gum Printing Issues?

jesse-m said:

Hi all,

Beginner gum printer here and I’m having a lot of trouble…particularly with muddy midtones and then pigment not washing off.

It is likely my error in my process, but it’s so hard to pinpoint what it can be. I also want to note that I’m using the Bostick and Sullivan kit which has l’Aquarelle pigments (never heard of the brand).

1. Pigment not washing off highlights/whites.
2. Really muddy and flaky shadows

Today I started thinking that maybe I am under-sizing or my pigments aren’t working well with my paper (Canson).

Appreciate any suggestions!

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Carnie Bob said:

your print is actuallly quite good for a beginner gum printer.. couple of things that I do

1. Hahnemhle Platinum Rag - pre shrunk by soaking in water is used for all my prints, no sizing required
2. Make sure you are using 14 BE gum
3. I use The Wet Print Pigments with great results.
4. You could use Ruby lith to hold back the white borders , the black created by the inkjet negative sometimes bleeds through due to excessive exposure.
4. If you are getting flaky shadows I would possible reduce the pigment load and increase the gum amount for a thinner coat.

have fun you are at a good starting point.

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BrianShaw said:

I'm impressed. Not an easy process. I tried and tried but never improved so gave up. The source of my problem seems to have been paper sizing and gum solution consistency/accuracy. And, possilbe, pigment selection and measurement. Looking forward to trying again some day.

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jesse-m said:

So many variables!

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Carnie Bob said:

Here is the biggest tip I can give you and it took me years of gum printing to get a handle on..

unlike silver , palladium, cyanotype where the image forms on the paper due to a reaction with the chemicals .

Gum is a wash off process where there is a simple starting point (exposure ) and ending point (exposure) that allows enough UV light to
penetrate the pigmented gum and harden in its reaction with Ammonium Dichromate. We have found with our LED lights that time can be anywhere from 1 1/2 min to 2 min.
After exposure the print is placed in water and the gum softens to a point where the non exposure areas wash off.

Most books will say 20 min in room temp is correct.... I on the other hand am very impatient and have found to elevate the temp to 85 -95 degree F with two baths, one to quickly remove the unwanted AD and start tickling the emulsion to the point it removes some pigment. At this point I move it to a second bathe of incoming water and with some agitation let the rest of the unwanted gum. In our space this step is never more than 4 minutes , once all the major gum is off we hang the print to dry for the next day coating and printing.

This is one of Calvin Griers tricks as well... Agitation is good, slow dissolve is painful.

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Andrew O'Neill said:

I have been quite happy floating the exposed print face down for 30 min in 20C water. I prefer a gentle approach.

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Carnie Bob said:

Ok, but you really need to watch out for air pockets with this approach as the gum will not wash off in these areas and create large circular blobs . I have always been a fan of initial agitation with process.

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