TSP as accelerator

[lensmagic]

Does anyone know of a formula for a metol film developer using trisodium phosphate [Sodium phosphate (tribasic)] as an accelerator?

 

[Mike Wilde]

I have not used one in b&w , but I did brew one for lith film use a few years ago, I recall. It is quite alkaline, not quite NaOH, but up there. It was for high contrast, and alos had HQ in there. It was basically almost a lith developer, but one that did not need to be mixed a+b for one session, I seem to recall.

I would consider looking to d-19 or d-85 and see how they work and the experiment with equimolar subtitutions of the tsp for the alkali
This would require a calculator, some paper, and a periodic table of the elements.

I am not a chemist (actually an electrical engineer) so I use an old CRC chemical text book to help me in these endeavours.

It contains tables of solubility limits, which are handy to consult before finding that something will just not dissolve the way you hoped it would.

 

[pgomena]

I used the search function on this portion of the forum and found this: (there was a url link here which no longer exists)

There were a whole bunch of other posts. I just put "Tri Sodium Phosphate" in the search window.

Peter Gomena

 

[Gerald C Koch]

You didn't mention the intended purpose of such a developer, so I'm guessing.

Pick any carbonate developer and substitute TSP w/w for the carbonate. This trick was used many years ago to produce better blacks in prints.

When TSP is dissolved in water some of it hydrolyses to form hydroxide ions and hydrogen phosphate ions. This raises the pH and developer activity. The resultant pH is higher than for a comparable amount of sodium carbonate. The down side is that aluminum phosphate may precipitate from alum based hardening fixers. To prevent this a citric acid stop bath, 30 g/l, should be used instead of the conventional acetic acid bath.

 

[lensmagic]

You didn't mention the intended purpose of such a developer, so I'm guessing.

Pick any carbonate developer and substitute TSP w/w for the carbonate. This trick was used many years ago to produce better blacks in prints.


Thanks to all who have responded. My intended purpose is a higher activity developer to be used, for example, on a subject with narrow contrast range. Plus, TSP, in and of itself, is a well-buffered alkali, much more so than sodium hydroxide.

I assume "w/w" means weight for weight.

 

[Photo Engineer]

Actually, at the pH that you will achieve by TSP or Na3PO4, the pH will drop rather rapidly and the developer will lose activity rather rapidly as the pH falls. It will also, like NaOH, dissolve hair, skin, wool and many other things due to the alkalinity so take precautions.

PE

 

[RPA]

Hi, First post. I was looking at an old (1944) Edwal processing book recently and notice some references to TSP. The book recommends that TSP be used with Glycin (what Edwal calls Monazol). However, there is a formula in the book for Edwal-36 (non-staining fine-grain developer) that uses it with chlorhydroquinone (1,4-dihydroxy-2chlorobenzene) (CHQ). I don't know if you can get CHQ or if there's a correlation to Metol, but here's the formula. Maybe it will help:

water 400 cc
sulphite 50 g
CHQ 25 g
TSP 9 g
Potassium Thiocyanate 5 g
water to 500 cc

 

[Photo Engineer]

Welcome aboard.

CHQ is a nice HQ like developer that is just a bit better than HQ, but is more expensive to make. It has fallen out of favor, but is still made last I heard, but at a very high price IIRC. It was discussed a while back here as well.

I should mention that my neighbor was one of the chief synthetic chemists at EK who made these new developing agent. He does not recommend it either. I talked to him about it. I'll bring it up with Grant Haist next time he visits Rochester and see if he has any thoughts as to its current worth in developers. (If I can remember. )

PE

 

[Gerald C Koch]

CHQ is a nice HQ like developer that is just a bit better than HQ, but is more expensive to make. It has fallen out of favor, but is still made last I heard, but at a very high price IIRC. It was discussed a while back here as well.PE

If I remember correctly CHQ was used in a number of warm tone print developers. There was one commercial MQ film developer which used it as a third developing agent. It can be used in film developers as the only developing agent where it acts like a mixture of metol and hydroquinone. It has sadly become an "orphan chemical" whose last commercial use was in developers. Two other orpahans come to mind, Glycin and Atomal. Both very nice developing agents for which there is no longer any demand. You can still get these chemicals from companies who specialize in synthesis of rare chemicals but the cost is very high.

 

[Ian Grant]

Chlorquinol hasn't been available as a developing agent in the UK since at least the early to mid 1970's. There was some concern about it's toxity back in the 70's.

I think Photographic grade Chlorquinol was made by Johnsons of Hendon whose chemical works manufactured a range of B&W & Colour developing agents as well as other photo chemicals from 1839 onwards , they pulled out of raw chemical manufacture around 1970-72 when the company was bought by Hestaire. As things like Chlorquinol would be made on a batch basis their last batch may have been some time - maybe even a few years - before depending on sales.

Chloroquinol is available but only in technical grades which can vary between 85-90% purity, the photographic grade was 98-99%, in addition it's still relatively expensive but usage outside photography means that price is dropping again.

As a dev agent it offered no benefits at all for film processing, it's use was for warm tone print developers, it's decline was mirrored by Phenidone's rise, and paper emulsions were changing as well at the same time.

Ian

 

[lensmagic]

Actually, at the pH that you will achieve by TSP or Na3PO4, the pH will drop rather rapidly and the developer will lose activity rather rapidly as the pH falls. It will also, like NaOH, dissolve hair, skin, wool and many other things due to the alkalinity so take precautions.

PE

PE, TSP's pH will drop rapidly, but relative to what? Sodium hydroxide?

 

[Photo Engineer]

Both have lower buffering capacity than Sodium Carbonate. In fact, Sodium Hydroxide has none for all practical purposes. TSP has little more. This is actually due to the high pH of TSP solutions and their rapid reaction with Carbon Dioxide in the air at that high pH. The solution wants to form Sodium Carbonate. Na3PO4 + CO2 + H2O -> Na2CO3 and NaH2PO4

PE

 

[eclarke]

Both have lower buffering capacity than Sodium Carbonate. In fact, Sodium Hydroxide has none for all practical purposes. TSP has little more. This is actually due to the high pH of TSP solutions and their rapid reaction with Carbon Dioxide in the air at that high pH. The solution wants to form Sodium Carbonate. Na3PO4 + CO2 + H2O -> Na2CO3 and NaH2PO4

PE

If you're using carbonate in a paper developer, what are the pitfalls when increasing the amounts? MQ type developer..Thanks..Evan Clarke

 

[Photo Engineer]

Carbonate at 50 g/l and at a pH of 10.0 - 10.5 is just fine as a buffer/alkali for a developer. At a higher concentration you face problems with a precipitate forming if the developer is cold enough. Or it just gets cloudy. And, it wastes carbonate. Avoid Potassium Carbonate.

PE

 

[Gerald C Koch]

As a solution of TSP absorbs carbon dioxide the pH will decrease to that of a solution of sodium carbonate. How fast this happens depends on the amount of carbon dioxide in the air and by how much contact the developer has with the air. Even if the developer is used in a tray, the process will be slow taking many hours to occur. If used in a tank you really need not worry. As the developer is exposed to CO2 it will still work but will have slightly less activity. At one time the use of TSP for developers was fairly common. But its use did not offer that much advantage over carbonate based developers.

 

[lensmagic]

Both have lower buffering capacity than Sodium Carbonate. In fact, Sodium Hydroxide has none for all practical purposes. TSP has little more. This is actually due to the high pH of TSP solutions and their rapid reaction with Carbon Dioxide in the air at that high pH. The solution wants to form Sodium Carbonate. Na3PO4 + CO2 + H2O -> Na2CO3 and NaH2PO4

PE

PE, I got to looking in this fairly old book, The Focal Encyclopedia of Photography which, in the entry for "Alkali," says: " . . . . Some alkalis, like sodium or potassium hydroxide solutions, change greatly in pH when the alkali concentration is slightly varied. Developers containing these alkalis rapidly lose their activity in use and are soon exhausted, since the alkali concentration and hence pH value rapidly drops as the alkali is used up.
"Other alkalis, like sodium carbonate or trisodium phosphate solutions, change their pH much more gradually in certain ranges as their concentration decreases. The reason is that these alkalis form a very small amount of sodium hydroxide when they are dissolved in water. As this hydroxide is used up, more is formed all the time. They thus behave like very weak solutions of sodium hydroxide which remain more or less constant during use.
. . . ."

It makes me wonder why TSP isn't used more often in developers.

 

[Ian Grant]

Carbonate at 50 g/l and at a pH of 10.0 - 10.5 is just fine as a buffer/alkali for a developer. At a higher concentration you face problems with a precipitate forming if the developer is cold enough. Or it just gets cloudy. And, it wastes carbonate. Avoid Potassium Carbonate.

PE

Interesting you say avoid Potassium Carbonate.

All the major manufacturers use Potassium salts in commercial liquid concentrate developers

Kodak use it in Dektol (liquid version also called Polymax in some markets) as well as many other developer, as do Ilford and the Agfa developers made by A&O.

Sodium carbonate is used in powder developers but isn't used in liquids because you can't get enough into solution for a reasonably concentrated developer, and often Potassium sulphite is used as well.

To reduce costs usually the sodium carbonate is replaced by a smaller quantity of Potassium Carbonate and small amount of Sodium or Potassium Hydroxide.

The ratio of the Potassium Carbonate to hydroxide substitution varies between companies but in the case of Agfa approx 60g of Sodium Carbonate is replaced by 12g Potassium Carbonate and 4g Potassium Hydroxide.

An Ilford's substitution is 40g Potassium Carbonate and 2g Potassium Hydroxide.

So there's no need to avoid Potassium carbonate,

Ian

 

[Photo Engineer]

The RATE of change is what is not mentioned in that article, nor is any practical experiment mentioned. Believe me that a TSP developer is high in pH and changes more rapidly than a Carbonate developer, and by a larger amount, thereby giving more variation.

TSP developers are used, but only where absolutely necessary and they are used with difficulty. Examples are E6 Color Developer and the 3 Kodachrome color developers. In fact, the use of TSP is one of the reasons these developers/processes are less stable. There is a set of instructions on how to adjust the pH of the E6 color developer based on color shifts which are mainly due to pH shifts.

PE

 

[eclarke]

The RATE of change is what is not mentioned in that article, nor is any practical experiment mentioned. Believe me that a TSP developer is high in pH and changes more rapidly than a Carbonate developer, and by a larger amount, thereby giving more variation.

TSP developers are used, but only where absolutely necessary and they are used with difficulty. Examples are E6 Color Developer and the 3 Kodachrome color developers. In fact, the use of TSP is one of the reasons these developers/processes are less stable. There is a set of instructions on how to adjust the pH of the E6 color developer based on color shifts which are mainly due to pH shifts.

PE

I asked about the carbonate because I saw a reference in one of my old books about replacing it in D72 with about 1/2 quantity of tsp for better blacks. I did try this but the results are subjective. Comparing the two recipes for D72, in a tray, developing FB paper, how would you say the rate of change between carbonate and tsp compare doing normal home darkroom developing?..Thanks..EC

 

[Photo Engineer]

I would not care to speculate with an exact value as it varies from developer to developer. There are a lot of factors involved.

The rate of pH change at equal molar concentrations will probably be close to zero for the Carbonate and will be a rather significant number for the TSP developer, just as a guesstimate. Open tray, 1 L in an 8x10 tray and working for an 8 hour session, you will probably see a larger change over 25 prints in the TSP than the Carbonate developer. I have tested pH values from 8 - 10 and find that the variation in first to last prints is smaller at lower pH.

PE

 

[eclarke]

And that's exactly the practical answer I was looking for, Thanks!!..Evan Clarke