Adventures in hide glue

[t5SQ]

Background: I read the Chiba Process PDF, and I've been trying to make a print from hide glue and watercolor pigment for a little while now, mostly failing with problems like dramatic staining issues, but with enough almost-successes to keep me at it. This was the first time I was able to get a few layers down with no catastrophe.

Materials

Paper: Canson XL Watercolor paper. I used the smoother side.
Pigment: Ancient Winsor & Newton Series 1 026 Ivory Black watercolor paint bought at a thrift store
Hide Glue: From Amazon, "Hide Glue Granules/Crystals, 251 Gram Strength"
Gelatin: 200 bloom beef leaf gelatin from pantry
Sensitizer: FAC from Jacquard cyanotype kit

Paper prep

Paper was soaked for about 10 minutes. Then I squeegeed it on both sides, spread 3ml of 3% gelatin onto the back side of the paper, and squeegeed the paper onto a piece of glass. The paper will stay on this glass throughout all layers, so registration will be simplified.

Now I prepared 9ml of 3% gelatin + 0.15g FAC and spread this over the front of the paper and let it dry for several hours, under a fan after the first hour or so. Then I exposed under my UV lights for 5 minutes, immersed in 0.3% hydrogen peroxide, and rinsed with several baths of warm water. Without this step, I get intermittent to constant horrible paper paper staining. I'm not sure I need so much gelatin, but I did try a single unpigmented glue layer, and that was not enough.

Image layers

For the pigmented glue solution: I made a 3% w/v solution of glue. Then I put 5g paint in a small bottle and added the glue solution to make 60ml total (this is about 8.3% w/v). The sensitizer solution is a 1.5% w/v solution of FAC in distilled water. I mixed 1ml of the glue solution with 1ml of the pigmented glue and brushed it on the image area, which here is about 6.75" by 5". I let it dry for about 20 minutes under a fan before exposure.

After exposure, I immerse the print in 400ml of 0.3% hydrogen peroxide solution, usually for about one minute as I get hot water from the tap. I then pour 1L of hot water directly into the hydrogen peroxide solution. After waiting for about 30 seconds, I pour more warm/hot water over the image to wash away the softened glue. This is typically enough to completely clear the glue from the highlights, and I remove the print from the water after maybe three minutes total, probably less.

So far I have not been precise with the temperatures, the hot water is just hot water from the tap. Since I pour that directly into the room temperature hydrogen peroxide, the development water is more warm than hot, and this does not seem to be warm enough to melt the gelatin holding the paper to the glass. A little bit more warmth and I can separate them.

Clearing FAC stain

I tried to clear some of the yellow stain with a 20 minute, 1% bath in disodium EDTA at room temperature. It didn't do much to clear the yellow, and there was a loss of density. I'm not sure what concentration/time would be appropriate, and I'm not 100% sure my EDTA dissolved fully.

Observations/comments

The exposure times for the layers, in order: 16, 44, 8, and 11 minutes. You can see that the high values from layer 2 were lost after layer 3 -- steps 10 and 11 have some density in layer 2, but are completely gone in layer 3. Next time I will probably try a negative with a smaller density range (this one is somewhere in the 1.4-1.6 range depending on whether you want any texture on the background). I will also print my layers from shorter to longer times, which I think will be a bit more predictable since I won't have to worry about the highlights washing away.

Images are here, layers 1-4 and then the attempt at clearing some FAC stain:

 

[koraks]

Interesting!

I'm kind of surprised you're getting a persistent stain from the FAC. I wonder if it's ultimately just iron hydroxide resulting from the interaction of the FAC and calcium carbonate buffers in the paper. You might try acid-soaking the paper first, then washing it before using it for printmaking.

Is it correct that your paint/glue mixture actually has more paint than glue in it?

You mention that hotter water might dissolve the gelatin sizing layer; that's a bit surprising to me since you harden it with FAC. Alternatively you could harden it with something like alum, or give more exposure and/or use more FAC for the sizing layer?

 

[AntonKL]

This looks promising!

I'm not sure if ivory black is the best choice for this process, apparently it's slightly alkaline, while the optimal pH is said to be slightly acidic.

The manual calls for an unhardened gelatin sizing layer, which has to be applied again for each image layer. Have you tried this?
I found it works well in principle, but I struggle to coat the pigment layer evenly on top of that, which will show up in the print. With chromium hardened gelatin otoh I got lots of staining.
Starch also worked IIRC but it's been a while and I did not write down any notes. If it does work it probably does not need to be re-applied between layers.

Regarding the FAC stain, I would start out by adding some 10g/l citric acid (CA) to the H2O2 bath. In my experiments I made the bath from CA and sodium percarbonate, so on top of the H2O2 it contains ~20g/l CA and ~7g/l Na2CO3 (or rather their reaction products). Never had any problems with staining, and I did notice the FAC was much faster to wash out in this bath compared to plain tap water.

I only ever experimented with single layer prints, onto which I brushed charcoal dust before the hot water wash. The result (if it works) is a very grainy 'lo-fi' print with intense blacks, looks great with black cats as the subject.
Sadly I've not yet found a way to reliably get a nice coating larger than 10x15cm and also the coated paper seems to age quickly, adding to the unreliability of the process. I think the latter is some interaction with the buffer in the paper.
So an acid wash or using unbuffered paper is definitely something to try.

I used considerably higher gelatin or glue concentrations, 4-6%, this can be kept liquid with urea and/or acetic acid.