Guming for it.

[buze]

I recently was very impressed with a few gum prints I saw on flickr (http://www.flickr.com/photos/jim_larimer/) and looking into my cupboard, I noticed I had pretty much everything to have a go at making gum prints -- apart from pigments.
So I went to the art shop, bought a dozen of tubes of various Windsor&N Watercolors, made a 10% Potassium dichromate bottle, and then sat down and started googling for recipes.

I was /amazed/ at the amount, and quality, of the material some of of you guys made available ! Katharine comes to mind, but there are a few other websites that are really great!

Still, I have a question
I realize I will not get a full, long tonal scale with one coat; but from the material I read of Katharine's, I sort of understand that I could do two (or more) exposures to cover the range:
+ One with a 'light' mix of the pigment, exposed 'a lot' to get the highlights in..
+ One with a stronger mix, exposed less, to get the shadows.

Am I getting this right ? This assumes of course a single pigment. I'm just trying to narrow the test field a little

 

[Katharine Thayer]

Still, I have a question
I realize I will not get a full, long tonal scale with one coat; but from the material I read of Katharine's, I sort of understand that I could do two (or more) exposures to cover the range:
+ One with a 'light' mix of the pigment, exposed 'a lot' to get the highlights in..
+ One with a stronger mix, exposed less, to get the shadows.

Am I getting this right ? This assumes of course a single pigment. I'm just trying to narrow the test field a little

Yes, that's what I've often done, but it also depends on what you mean by a long, full tonal scale; I'm starting to think we need some precise way of saying what we mean by that. I've been thinking about writing a new page for my site that goes into that in more depth, but that's not going to happen right away.

You can get something like a full tonal scale in the sense of values going from dark to light in one coat, but not what I'd call a "full, long tonal scale"

http://www.pacifier.com/~kthayer/html/kids.html

and the best way I've found to print a full, long scale is multiple printing. However, there was recently a discussion on the alt-photo forum about using a heavy pigment mix in combination with gross overexposure and brief development in dilute bleach that is also worth considering. I've not had good results with it so far, though I've only had time to experiment with it briefly, but others have; you might want to check that out.

Dead Link Removed

And I agree, Jim Larimer is doing some nice work in gum.
Katharine

 

[buze]

There we go, had a gum-session ! Early impressions are very good! I tried a few color tints and then try to concentrate on making a couple of 'good' monochromes using a known negative, and it worked fairly well !
I seems easy to use one's 'good judgment' to layer things, without having to be clinicaly precise about it.

One thing I must do better next time is to 'pre-shrink' the paper for longer, it still had a tendency to not lay flat, making registration difficult. I must also make some color separation BEEEEEEEEEEEP negatives

I'll post a scan when the paper is dry...

 

[Katharine Thayer]

Great! Just one comment: whether the paper dries flat or not may have more to do with the paper itself and how it is dried than the length of the soak, in my experience. I use a paper that's a little thin and crisp that has a tendency to curl while drying, and I always flatten it between blotters under weight before printing on it.

 

[buze]

Here goes; this print was made with the method I envisionned earlier on; rather dilute layer 1, exposed at N+1 (thats 5 minutes here, N is 3 or so) then a second layer with thicker pigment exposed at N-1 (1.5 minute or so). developed about 20 minutes each. Pigment is Ebony Black.
There is a bit of staining, visible mostly from the back of the print; not sure how to sort that out...

(from my Flick Page)

 

[Katharine Thayer]

I'm impressed; this is great, especially for a first effort. Welcome to Gum World!

 

[JimLarimer]

Thank you, Buze and Katharine for your kind remarks! Recently I was given a drum print dryer and it has solved the problems that I was having with prints warping during air drying. I hang my print to drip dry for about 20 min and let the image harden, then I place it in the drum dryer on "low" for about 15 min and I end up with a print that is dry and curled a bit but flat and easy to register my negative to. I sometimes stop my development before the emulsion is completely "washed away" so the "hang time" allows for the setting of the emulsion (gum) so that the heat from the print dryer causes no problems.
Keep up the good work, Buze! Your first print is really very good!! Jim

 

[Katharine Thayer]

There is a bit of staining, visible mostly from the back of the print; not sure how to sort that out...

Buze, somehow I missed this part the first time I read this post. What color is the stain? The color of the pigment, or a yellow/tan/brown color?

 

[gbenaim]

Buze and Jim,

Could you give a beginner a quick idea of the chemicals and process involved? Thanks,

GB

 

[Katharine Thayer]

I'm not Buze or Jim, but I just happened to be here, so hope you don't mind if I answer the question.

Materials required: ammonium or potassium dichromate, gum arabic, and pigment (dry or in the form of watercolor paint).

How it works: when the above ingredients are mixed, coated on paper and exposed to UV radiation, the gum arabic that has been exposed undergoes a reaction (crosslinking) that makes it insoluble. The print is then placed in water, where the unexposed, and therefore still soluble, gum dissolves into the water, leaving an image made of insoluble gum holding pigment. That's it.
kt

 

[JimLarimer]

Hi GB....As a beginner I found Katharine's web site to be of tremendous help in learning how to do gum prints. I would suggest that you visit...and be prepared to learn a whole lot of valuable information!! Jim

http://www.pacifier.com/~kthayer/index.html

 

[gbenaim]

Thanks Jim and Katharine. Is the process the same when done over a platinum print? And do you need some sort of registration to do multiple exposures?

 

[Katharine Thayer]

I've never done gumovers, but I personally suspect that while the essential gum process is the same as for straight gum, the technique is necessarily somewhat different. For one thing, with a gumover process the essential bones, the tonal structure of the image, is mainly provided by the underlying print. With straight gum, the gum itself has to provide the structure of the image. So you'd probably make different choices about pigment concentrations and the like.

Registration: yes, you need to register for multiple printings, but in my experience you don't need a complicated method for doing that. I just monitor the drying and print again when the print has dried to where the negative fits the image. When I was really into production gum printing, I could tell just by the feel of the paper when it was ready to print again, but I've changed paper since then and haven't been printing that industrially lately, so I don't have that facility with my present paper. So I just take the paper down every now and then and put the negative over the image; it's fairly easy to tell when it's in register. kt

 

[buze]

Buze, somehow I missed this part the first time I read this post. What color is the stain? The color of the pigment, or a yellow/tan/brown color?

Katharine, the stain is the same color as the pigment. My guess is that I need some sort of size before the first gun layer... I bought some 'gesso' and will try a diluted mixture of that to see if it helps for my next attempt.

Jim, I tought I would be able to dry the print flat on a mesh to help with the flatness, but the prints are just too 'wet' to do that; and I cannot blotch them immediately like I do with the other processes, so right now I have to hang them.

gbenain, Katharine website is a bible of information; however I must confess I did disregard some of the information because I'm lazy and wanted to get going fast mostly I think the 'pigment choice', stability and all that is a bit arcane for a beginner, so I just picked a bunch of tubes at the art shop and it turns out they are almost all on Kat's Approved List anyway

Has any of you experts tried the 'Sullivan way' of dry mounting the paper on a piece of circuitboard ? it looks very interesting, and solves lots of problem at once (flatness, registration, drying etc)

 

[Katharine Thayer]

gbenain, Katharine website is a bible of information; however I must confess I did disregard some of the information because I'm lazy and wanted to get going fast mostly I think the 'pigment choice', stability and all that is a bit arcane for a beginner, so I just picked a bunch of tubes at the art shop and it turns out they are almost all on Kat's Approved List anyway

Is Kat some other person, or is that supposed to refer to me? If the latter, it's rather surprising to me to learn that I have an Approved List for pigments, since my position about pigments has always been just what I say at the top of that page: Choice of pigment has more to do with personal preference than with whether the pigment is good for gum, since in my experience there are no pigments that don't work for gum. I certainly have no approved list for pigments for gum.

The page on pigments was written more than five years ago and is one of the last of the original site to be revised and updated. The section on fugitive pigments is outdated, since Winsor & Newton, the last manufacturer to carry some of those fugitive pigments, has discontinued them since. At any rate the page is too text-intensive; thanks for the reminder that it needs to be redone.
kt