More gum dichromate

June 21, 2008

I’ve read in more than one place that gum printing is both the simplest printing method to use and the most difficult to master. I would agree with both assessments. Pretty simple ingredients to start with but it can be very challenging to get a working image. I’m at single color, single pass printing and trying to get a handle on exposure and pigment mixing.¬† And I will likely be here for a while.

To that end I’ve got another batch of prints to play with. This time I’m using a bit nicer paper, some Weston Diploma Parchment. Pretty good stuff and I can tear down the sheets into four pieces each large enough for a 4×5 negative. Makes a good practice size.

Lessons learned :

1) It is easier to apply the gum and dichromate with a foam brush but a foam brush will raise the grain of the paper. Doesn’t matter how light the touch, it just seem to happen with the WPD.

2) Hake brushes shed hair. Cheap brush, expensive brush, they both shed. The good Joto brush less so but it still means watching for hairs stuck in the gum.

3) It doesn’t seem to take much UV at all to start the gum hardening. Prep’d a few sheets about 11am this morning and I thought it was dim enough in the basement to work out of the dark room. Seems not so. Had a dickens of a time getting those to clear, even rubbing the wet print it wouldn’t release the pigment. However sheets prep’d in the darkroom with just the red safelight (need to get a 40W yellow bug bulb) did much better.

4) Gum prints much faster than I expected. Got reasonable exposure in 2 minutes of noon day sun. Didn’t worry about the contrast issue, just used direct sun. It did produce a bit of a contrasty print. And I am seeing just a little bit of a POP image in the print as I remove it from the contact printing frame. During the first session I did not see any fugitive image.

5) Sizing the WPD with gesso works better than unsized paper. Pigment sinks too deep it seems and doesn’t like to release. I need to size some paper with gelatin and glyoxol and experiment with that too.

6) Clearing the print is taking quite a long time. Could be pigment choice, could be gum has hardened too much, could be water pH, could be unsized or not the right sizing of the paper… Lots and lots of variables here. Slowly getting a handle on them one at a time.

Here is a shot at un-sized paper and the hake brush. Much better paper finish (not “fuzzy”) but really didn’t like to clear at all so the print is a bit muddy and low contrast. 1:1 gum and potassium dichromate with lamp black as the watercolor paint. This sheet was also coated outside the darkroom in what I thought was low light but must be just a little too much sun coming in even at 11am and on the west side of the basement.

Wabunsee County School House

Also I wonder if maybe I shouldn’t add a little bit more pigment.

Next is a bit better result with gesso sized paper and using a foam brush. The scan doesn’t show the paper surface but it is a bit on the fuzzy side. Same 1:1 gum and potassium dichromate. Also this time

Pillsbury Crossing Tree

More pigment this time (maybe 1 1/4″ worm this time instead of 1″ or a bit less the first time).

So key things to walk away with are:

You can’t coat the paper in too dim of a light.

Clearing the images takes a lot of patience.

Foam brushes are easy to use but with the WPD paper I don’t like the finished look.


Leave a Reply

Please log in using one of these methods to post your comment:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s

%d bloggers like this: