The Fish Gelatin process - first CMYK prints

[NedL]

I have never heard of a fish gelatin process, but about an hour ago I had a meal of smoked Haddok that had exactly the same colour of the stone building in the left of your picture. If you used octopus, would it have the same colour as their ink?

Hi Clive.
I know you are joking, but....
In the 1850's, Gustave le Gray used rice starch and isinglass in the iodizing stage to prepare his waxed paper negatives. I use his method of preparing rice starch when I make salt prints or when I make "Pelegy process" calotypes. I've never added the isinglass. Here is a reference, see page 8: Gustave Le Gray Waxed Paper Process

 

[cliveh]

Hi Clive.
I know you are joking, but....
In the 1850's, Gustave le Gray used rice starch and isinglass in the iodizing stage to prepare his waxed paper negatives. I use his method of preparing rice starch when I make salt prints or when I make "Pelegy process" calotypes. I've never added the isinglass. Here is a reference, see page 8: Gustave Le Gray Waxed Paper Process

Thanks Ned, that was interesting and I still have that wonderful pinhole image you sent me.

 

[PGum]

I also wonder why the CMC is needed as gum alone works well with dichromate.

With the CHIBA system, the free radicals formed during the H2O2 development are not able to crosslink gum arabic in sufficient time, or at all.

Speculating:
The CMC addition is likely inhibiting the dissolution of gum arabic possibly by complex coacervation - essentially the two colloids binding to each other. Since CMC will crosslink somewhat in this system, it seems to grab on and hold the gum arabic. I have found that this indirect crosslinking approach is vulnerable to long rinses, and the complex can re-dissolve and wash out the image. Using gum arabic in the CHIBA system remains dicey.

 

[AntonKL]

Using gum arabic in the CHIBA system remains dicey.

With waxy maize starch, if sugar was also present in the emulsion, I observed the opposite of hardening. The exposed areas became easier to wash off.
I did not manage to get proper images with this effect though.

 

[PGum]

I have not made any attempts with waxy maize in the CHIBA system, regardless that is an unusual effect. I have seen a similar ”positive process” effect with ferric chloride and gum arabic but that is quite a different animal.

 

[Jon O'Ricky]

With the CHIBA system, the free radicals formed during the H2O2 development are not able to crosslink gum arabic in sufficient time, or at all.

Speculating:
The CMC addition is likely inhibiting the dissolution of gum arabic possibly by complex coacervation - essentially the two colloids binding to each other. Since CMC will crosslink somewhat in this system, it seems to grab on and hold the gum arabic. I have found that this indirect crosslinking approach is vulnerable to long rinses, and the complex can re-dissolve and wash out the image. Using gum arabic in the CHIBA system remains dicey.

A lot of pitfalls there then. I did a test with the GA/CMC mix and never again.

 

[NedL]

In case anyone in the US is interested...

I just looked at the Kremer Pigments website again, and now instead of $12 flat shipping to the US, it says:

Note: Your shopping cart contains items that are subject to special ordering or shipping regulations.
We will send you an offer.

I guess this has to do with the de minimis rule changes. I didn't go further to see what kind of offer they would send to me. Am thinking about trying this over cyanotype....