Hydroquinone in high concentration

[iakustov]

I wanted to try Chemco lith developer with Fomatone and Slavich paper using the original formula, except for potassium formaldehyde bisulfite - I replaced it with sodium formaldehyde bisulfite:

Concentrate A:
Water 52 C - 500 ml
Hydroquinone - 135 g
Sodium formaldehyde bisulfite - 98 g
Diethylene glycol - 118 ml
EDTA - 0.26 g
KOH 45% - 2.8 ml
Water to make 1000 ml.

OK, in an hour I was able to completely dissolve 135 grams in 600- 700 ml of water at 52 C.
After pouring sodium formaldehyde bisulfite the solution became very dense and looked like a porridge or wallpaper glue, but after adding diethylene glycol it became transparent again. I added everything required and the final concentrate was really clear (I swear) with no residue, I poured it into two 500 ml bottles and started to prepare concentrate B.

After ~2 hours as I was preparing the working solution (1 A + 1 B + 4 Water) I noticed that concentrate A was full of those hydroquinone small "needles". I stirred it before adding into the working solution and started printing.

Now concentrate A (two 500ml bottles) looks like this:


What did I do wrong?

It looks like hydroquinone solubility in water depends on the temperature: 5 g in 100 ml at 5C, 20g at 50C, 56g at 70C. Could this be the reason so that after solution cooled down hydroquinone started to crystallise? Unfortunately, I have very limited chemistry knowledge.. But as there is no mention about this in the sources for the formula, I tend to think I did something wrong.
Maybe someone had experience with developers having highly concentrated hydroquinone?

As for my experiment - the prints came out fine, with more pronounced effect on Slavich. Development was in 6-8 mins range for both papers. Next time I will prepare the working solution straight away, avoiding the concentrates.

 

[koraks]

As you noted, there are limits to how much hydroquinone will dissolve - and stay in solution upon cooling. The addition of a sodium salt may further decrease the amount of hydroquinone that wants to stay in solution. You could try adding some alcohol (ethanol); it tends to help somewhat. Personally I'd just mix this concentrate at half strength or so and use double the amount for the working solution. This may impact shelf life, which is likely limited to a few months anyway especially in a partly filled bottle.

 

[dE fENDER]

...
What did I do wrong?
...

Everything is ok as it should be. If you prefer concentrate, you have to heat the bottle with crystals under hot water before mixing.

 

[Donald Qualls]

Everything is ok as it should be. If you prefer concentrate, you have to heat the bottle with crystals under hot water before mixing.

Of course, there is the issue that the partial bottle is no longer the correct proportions after decanting liquid at room temperature. The liquid that came off was deficient in hydroquinone, and the remaining contents of the bottle will have excess.

 

[iakustov]

Thanks everyone for clarification, it looks clear now.

 

[iakustov]

I have made some test prints in Chemco and I like the results.
Fomatone 131 paper toned in Selenium:



Thanks dE fENDER for your suggestions and recommendations regarding this developer.

 

[grainyvision]

Just for reference for anyone stumbling onto this thread in the future, it is possible to split this developer (or other hydroquinone rich solutions) into a 3 part mix or incorporate an alternate solvent to keep the hydroquinone more easily in solution. Polypropylene glycol can reach at least 10% solubility with hydroquinone (ie, 100g per 1L) and is fairly neutral in terms of developer effects. Triethanolamine (TEA) can reach at least 20% solubility with hydroquinone but does have several different effects including change in pH and specifically in high concentrations can change the behavior of infectious devleopment. HQ-TEA may not be the best water-free solution if you split into a 3 part mix. A bottle I have of it mixed 6 months ago discolored into a darker brown, but still works as expected in lith developer formulations. The HQ-glycol solution though has remained pristine and almost clear in a half empty bottle for several months now.