PC-TEA gone bad (crystals) ?

LarsAC · Aug 2, 2016

Hello,

a few days ago, I mixed PC-TEA using a stock solution of Phenidone in Glycol.

After two or three days, the PC-TEA shows a large amount (about 3/4 of the height of the bottle) of needle-like crystals. Shaking the bottle does not bring them back into solution (had not expected that). The bottle was in a rather warm room (attic), definitely not below 20°C. The Phenidone/Glycole stuff looks fine, without crystals or precipitate.

Any ideas what might have gone wrong ?

Thanks in advance,
Lars

baachitraka · Aug 2, 2016

Strange. Me mixed some weeks ago if not months and they are fine till last Sunday.

I am curious about crystal growth too.

Nevertheless, a versatile developer.

Gerald C Koch · Aug 2, 2016

Problems like this point out the importance of keeping a darkroom notebook. As each ingredient is added the amount is noted in the book. Sadly that's not possible here. But perhaps too much ascorbic acid was used. However without proper notes it's impossible to tell now.

It's really pointless to speculate. Dump the bad stuff. My advice would be to start a notebook and mix up a fresh batch. Double check your amounts and that you are using the right chemicals.

Of all the developers discussed on APUG these concentrated staining formulas seem to cause the most trouble.

LarsAC · Aug 3, 2016

Thanks for the various thoughts and ideas. I was quite sure I mixed a correct amount, but who knows. Will try again, got enough TEA left.

Lars

baachitraka · Aug 3, 2016

9g - Ascorbic acid

0.25g - Phenidone. No scientific measure was there. Ratio was 40:1 and that equates to 0.225g of Phenidone but I use 0.25g of it.

100ml - TEA

LarsAC · Aug 17, 2016

Redid a batch yesterday. No crystals so far. I guess, I did not heat TEA sufficiently last time. Heated to 180F now and all ascorbic acid dissolved well. Looking forward to first developments on the weekend.

Lars

John Wiegerink · Aug 17, 2016

LarsAC said:
Redid a batch yesterday. No crystals so far. I guess, I did not heat TEA sufficiently last time. Heated to 180F now and all ascorbic acid dissolved well. Looking forward to first developments on the weekend.

Lars

I thought Gainer said to bring the TEA up to 250 F?

baachitraka · Aug 17, 2016

I did not heat the TEA rather warm/hot water bath until everything was dissolved.

stormpetrel · Aug 17, 2016

Hello

PC-TEA prepared with glycol is not PC-TEA. Once diluted pH might differ from the original recipe and the results too. It would be better to call it PC-GLYCOL to avoid confusion.

I prepare my PC-TEA and 510-PYRO (which is PC-TEA + pyrogalol) on the hot plate with 99.9% pure TEA.
Once it reaches 150C (300F), I remove it from the hot plate, I pour the ascorbic acid which dissolves very quickly on the magnetic stirrer then I add the phenidone which dissolves also very quickly.
I prepare a bottle of PC-TEA every 6 months since 2013 and I never had a problem.
I still have a bottle from 2013 3/4th empty I keep to do do a shelf life check every year and it is as good as the first day it was made!

John Wiegerink · Aug 17, 2016

stormpetrel said:
Hello

PC-TEA prepared with glycol is not PC-TEA. Once diluted pH might differ from the original recipe and the results too. It would be better to call it PC-GLYCOL to avoid confusion.

I prepare my PC-TEA and 510-PYRO (which is PC-TEA + pyrogalol) on the hot plate with 99.9% pure TEA.
Once it reaches 150C (300F), I remove it from the hot plate, I pour the ascorbic acid which dissolves very quickly on the magnetic stirrer then I add the phenidone which dissolves also very quickly.
I prepare a bottle of PC-TEA every 6 months since 2013 and I never had a problem.
I still have a bottle from 2013 3/4th empty I keep to do do a shelf life check every year and it is as good as the first day it was made!

Yes, that's the ways I remember Gainer describing how to heat and mix it, b ut I thought he said 250 degrees F?

Gerald C Koch · Aug 17, 2016

What was mixed glycol and not TEA will not develop film for an alkali is needed.

With TEA being alkaline ascorbic acid should dissolve without heating. All that is required is a bit of patience and perhaps some gentle warming in a water bath. Heating these TEA based concentrates to a higher temperature only causes some decomposition.

Gerald C Koch · Aug 17, 2016

stormpetrel said:
Hello

PC-TEA prepared with glycol is not PC-TEA. Once diluted pH might differ from the original recipe and the results too. It would be better to call it PC-GLYCOL to avoid confusion.

I prepare my PC-TEA and 510-PYRO (which is PC-TEA + pyrogalol) on the hot plate with 99.9% pure TEA.
Once it reaches 150C (300F), I remove it from the hot plate, I pour the ascorbic acid which dissolves very quickly on the magnetic stirrer then I add the phenidone which dissolves also very quickly.
I prepare a bottle of PC-TEA every 6 months since 2013 and I never had a problem.
I still have a bottle from 2013 3/4th empty I keep to do do a shelf life check every year and it is as good as the first day it was made!

Adding ascorbic acid to hot TEA can cause a very energetic reaction and might be dangerous. Best to add it first and then warm if necessary.

John Wiegerink · Aug 17, 2016

I'm sorry, but I thought the OP was mixing the Phenidone in Glycol (small amount of glycol) to get it to be much more soluble in the TEA solution. I 'm sure Gainer recommended mixiing the phenidone in glycol fist (HOT) and then in the 250 degree F TEA. I guess I'll have to search for the true method he talked about.

Photo Engineer · Aug 17, 2016

One thing to remember is that TEA is often a solid at room temperature depending on a number of factors. I have seen entire batches of TEA solidify while another batch next to it is still liquid.

PE

John Wiegerink · Aug 17, 2016

Yes PE, I have to warm my 510-pyro a little before I mix it with H2O or I can't even pour it to measure. Funny that batches are that much different. I must have gotten one of the thicker batches I guess.

stormpetrel · Aug 17, 2016

Gerald C Koch said:
Adding ascorbic acid to hot TEA can cause a very energetic reaction and might be dangerous. Best to add it first and then warm if necessary.

There might be an exothermic reaction but it is not measurable with the thermometer. At 150°C, it takes ~5min to fully dissolve the ascorbic acid crystals which explains why there is no energetic reaction. If the crystals were dissolved instantaneously, it would be very energetic indeed!

At 80°C it took me HOURS of magnetic stirring to fully dissolve the ascorbic acid. I have increased the temperature of the TEA by 10°C steps up to 140°C-150°C and found that it was the right temperature for me. I always heat the TEA in a lab beaker with a thermometer so I know when it is time to remove it from the hot plate.

We all agree that ascorbic acid degrades very quickly with the temperature in air however, I wonder if the ascorbic is not too much affected by the temperature when dissolved in hot TEA poor in oxygen?
Anyway, I could not see any difference between film developed in my first batch of PC-TEA prepared @ 80°C and the last batch prepared @ 150°C.

For people playing with TEA, I would highly recommend to read this datasheet from DOW
www.dow.com/scripts/litorder.asp?filepath=amines/pdfs/noreg/111-01375.pdf
There are very useful information about this chemical (pH, degradation temperature...)

stormpetrel · Aug 17, 2016

Photo Engineer said:
One thing to remember is that TEA is often a solid at room temperature depending on a number of factors. I have seen entire batches of TEA solidify while another batch next to it is still liquid.

PE

The proportion of MEA might affect the viscosity & freezing point ?
Viscosity of MEA @ 30°C 20 Centipoise, freezing point 10°C
Viscosity of DEA & TEA @ 30°C 400 Centipoise, TEA freezing point 21°C

Photo Engineer · Aug 18, 2016

Actually, some samples of TEA sold for photographic use are quite impure and may contain all 3 amines.

PE

Gerald C Koch · Aug 18, 2016

I buy TEA from the Chemistry Store. They include an MSDS so I know the purity of the product.

LarsAC · Aug 19, 2016

I used glycole only to make a stock solution for Phenidone (1+10 in glycole which facilitates measurement).

I read different approaches to heating, the original source said to heat up quite warm. Later, I found other sources (Pat Gauner himself IIRC) where he recommended 150F or even simple warming to ease stirring.

Lars

Photo Engineer · Aug 19, 2016

Lest we return to old arguments, remember that all of these organic solvents are flammable to some extent and they have a flash point that should not be ignored.

Many are toxic and so should not be heated in pots or pans intended for cooking food.

Be careful.

PE

Gerald C Koch · Aug 20, 2016

One really needs to know just what they are using. Read the MSDS that should have been sent with the TEA. The seller is required by law to supply one. Unless the sample is pure TEA then the pH will be off.

PC-TEA gone bad (crystals) ?

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