ModernLith, or: How I learned to stop worrying and love modern papers

I've formulated a developer I've titled "ModernLith". This is a developer that is ideal for lith printing on modern "non-lithable" papers. Though like all lith printing formulas there is plenty of room for modification. I won't bother copy-pasting the entire thing as it's extremely long.. But I'll give a quick summary and my favorite results here.

Full post with all of the details and additional scans etc: https://grainy.vision/blog/modernlith

Favorite papers:
* Ilford MGV -- Very flexible giving good results in all modifications and not overly slow to develop. Can give anything from cool brown tones to warm sepia colors.
* Fomapseed 133 RC -- Trends toward colder tones, especially with benzotriazole. Best suited for MOD2
* Ultra.EDU Ultra FB -- Trends toward cooler blacks and warmer highlights. Can be quite grainy, seems best suited for MOD2

The working solution formula:

• 10ml of hydroquinone 10% solution in propelyne glycol (1g of hydroquinone)
• 10ml ascorbic acid 8% solution in propelyne glycol (0.8g of ascorbic acid.. Can also be substituted most likely with ascorbic acid salts)
• 4ml of 20% sodium sulfite solution (0.8g sodium sulfite) — can be in the range of 3-6ml
• 60ml potassium oxalate 10% solution (6g potassium oxalate)
• 4ml potassium bromide 10% solution (0.4g potassium bromide)
• Add to 940ml of water, rinsing the containers to ensure all glycol solutions are mixed in
• 60ml sodium carbonate 20% solution (12g sodium carbonate) — probably ~10 or 11g potassium carbonate is actually recommended here, significantly easier to dissolve. 20% for sodium carbonate is almost the solubility limit

Benzotriazole (~10ml of 0.1% solution) can be substituted for potassium oxalate, though with shorter tray life, and significantly cooler tones on many papers, and it will require ~1 stop more exposure.

There are modified formulas:

* MOD1 -- Mix standard 1L solution, then add 2ml of potassium bromide 10%, 1ml of sodium sulfite 20%, and 10ml of ascorbic acid 8%. --Gives warmer tones with most papers. Can give poor low contrast results on some papers.
* MOD2 -- Mix standard 1L solution but with only 5ml of ascorbic acid. Tends to give colder results. Tends to work better on many non-Ilford RC papers.

Favorite results are attached.

Very interesting formula, and very nice results, but can you provide me some rationale for the addition of Potassium Oxalate?

Rudeofus said:

Very interesting formula, and very nice results, but can you provide me some rationale for the addition of Potassium Oxalate?

Click to expand...

It was based on this paper: https://onlinelibrary.wiley.com/doi/abs/10.1002/recl.19450641004 The concepts that are chained together was a reference that ascorbic acid will prevent sulfite from oxidizing in alkali solution. Then by using that paper about oxalate, I mixed in oxalate to prevent the ascorbic acid from oxidizing as quickly. I'm no chemist so have no real way of testing if my understanding is completely correct.. however, I've done some practical control tests.

* Hydroquinone only -- very short tray life (<1 hour), other pictorial problems with modern papers ( some papers require such low amounts of bromide for infectious development to occur that fog develops, extremely uneven development, too much midtone development, etc)
* hydroquinone+ascorbic acid -- Better tray life (1-1.5 hours), tendency for highlights and midtones to develop too quickly. Sensitive papers from above can become significantly more tolerant of increased bromide levels
* hydroquinone+ascorbic acid+benzotriazole -- in some ways better than oxalate for cold tones, but tray life is no better than the ascorbic acid only combo.
* hydroquinone+ascorbic+oxalate -- best tray life seen (2-3 hours maybe longer, though various bad effects begin to pile up after 2.5 hours on most papers). perfect lith effect on most papers, though some papers can still have a bit more midtone development than I like. (can probably add more oxalate to combat that, or a tiny bit of benzotriazole)
* hydroquinone+oxalate -- no notable difference to tray life (in 2 control tests they gave conflicting results), oxalate in very high amounts (25g+per liter) will slightly restrain midtones, but this effect may be due to contaminants. (iirc I'm using 98% grade with chloride listed as a potential contaminant)

edit: my personal hypothesis of how it works is as so:

Ascorbic acid will prevent sulfite from being oxidized by air/oxygen in water. The sulfite will still be oxidized by recovering oxidized hydroquinone. The ascorbic acid will then be oxidized both by being "sacrificial" for sulfite and also through the natural process of developing the silver halides. When ascorbic acid develops a grain, it will release an acidic somewhat unreactive radical that basically slows hydroquinone development of nearby grains. Oxalate will then react with the fully oxidized ascorbic acid to oxidize itself (supposedly to plain CO2?) and restore the ascorbic acid, but not the radical. I suspect that the ascorbic acid radicals produced in development naturally decay into fully oxidized ascorbic (can't remember chemical name) and/or react with the extremely reactive hydroquinone radicals that are responsible for infectious development. End result is that the ascorbic acid helps to develop the induction image, but then the acidic radicals produced prevent hydroquinone from attacking it too vigorously. The hydroquinone radicals etc do accumulate in shadows though and thus infectious development still happens. The oxalate is still quite a bit of a mystery in how it works though. It definitely has anti-fogging properties since it behaves like benzotriazole, but also will make tray life better.