Recent content by AntonKL

Your issue with citric acid might be related to what I once saw with sugar+starch. I have no idea on the underlying mechanism however.

You can make do with less sulfite, I mixed mine with just 20g to 250ml and it still works fine after 2 years.

Ah that's still a lot more than the 6g/m2 we use with the direct carbon approach, so no quick drying times (but of course it can be prepared in advance just like you did). With his 60ml 10% / A4 he uses a whooping 96g/m2. I suppose that's what he and his target audience are used to from the...

Wow that's really cool! How much gelatin did you use if you got results so quickly? Or did you have gelatin paper lying around? The thickness they use in the article I linked does sound absurdly high.

The manual makes no mention of that, though I haven't done it personally https://www.alternativephotography.com/rawlins-oil-print-process/ A japanese twitter user beat the author to it, he also uses a UV enlarger and has a lot more patience than I. This account put me on track with the dust-on...

I dust it on the humid gelatin yes: After the cold H2O2 bath comes a brief cold wash, then I put it face down on a glass plate and carefully squeeze out the water. An older approach that also works with some gelatin types was just dabbing it dry with kitchen paper. I also played around with...

Yes but only as an experiment, I got better looking results when dusting onto a regular direct carbon print (with black pigment in the gelatin and the stain prevention layer in place). Also the dusting pigment must not be too fine or it will cake together and prevent proper washing off.

I think in the direct pigment processes the pigment in the gum/gelatin acts similar to a half-tone screen too: When experimenting with brushing charcoal dust on "chiba direct carbon" prints (after the H2O2 but before the hot wash) I tried fully leaving out the pigment from the gelatin so I could...

Copper(II) chloride has two moles of chloride per mole of copper, but we only need one (plus some 5-10% excess for full, timely conversion). You would need to mix it with another copper salt like the sulfate, sulfamate, perhaps also lactate or acetate, but not citrate, malate etc. Copper(I)...

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.

Some updates / additional details to the original process as I will move on to other projects (I want the reader - i.e. me in a year or so - to be able to reproduce the process steps just using this post, so some things may be redundant). Enlarger Setup I'm using a Meopta Axomat with the lamp...

They used to use this as a positive process, by toning the unexposed parts with gallic acid. The exposed parts became more soluble which aids clearing, to amplify this they let the gelatin/ferric/TA mix hydrolyze for a couple days before coating. See e.g. ch. 8 in Die Lichtpausverfahren, die...

@Jan de Jong the system is pH sensitive, if you just mix copper sulfate and AA it does not do much. For it to be able to plate out metallic copper or quickly react to form copper (I) halides you need to raise the pH just slightly by adding e.g. NaHCO3 or Na-Ascorbate to the mix. Raising the pH...

So everything turned black/brown? Or yellow? The "whites" are supposed to be strongly yellow before fixing (unless you pre-treat the paper with chloride/bromide instead of alkali). You can get stable images by first fixing with alkaline (Na-)Thiosulfate solution, then toning with either silver...

It won't act as a boric acid / borate buffer, instead just like NaHCO3 as additional quickly soluble alkali. Boric acid buffers usually work at pH>8 while the working pH here is somewhere between 3 and 5 IIRC. It will get rid of the bubbling though so it might still be worthwile.