Need help with filtering PC-TEA

aldevo · Sep 24, 2007

Well, I hand-mixed a new 1L batch of PC-TEA and tested it. Unfortunately, my test roll revealed a fair bit of very small particles on the developed frames. Based on the scans, I'd say the particles vary somewhere between 0.5 micron to maybe 2,3,4 micron.

If possible, I'd prefer not to write-off the entire 1L batch (I'd need to order new Phenidone and Vitamin C; a bit pricey) and I was wondering if people had suggestions on how to reliably filter out these particles before use of the working solution.

The PC-TEA stock solution is very viscous so it would seem to make sense to filter the working solution. I dismissed coffee filters because these will introduce paper fibers into the solution based on previous experience.

Any thoughts?

Ian Grant · Sep 24, 2007

Are you sure they are from the developer and not the fix or wash water.

I do use coffee filters to filter my solution and I've never had paper fibre problems. But remember even with proper chemical filter papers it's normal to run some solution through to remove any potential particles on the paper then refilter with the rest of the solution.

Ian

aldevo · Sep 24, 2007

Ian Grant said:
Are you sure they are from the developer and not the fix or wash water.

I do use coffee filters to filter my solution and I've never had paper fibre problems. But remember even with proper chemical filter papers it's normal to run some solution through to remove any potential particles on the paper then refilter with the rest of the solution.

Ian

Great question!

Actually, I'm 99.9% certain it's the developer because the problem does not occurr when I develop film in Pyrocat-MC supplied by the PhotoFormulary. The filter on the tap water used for stop/wash seems to be in good, working order.

The suggestion to pre-wet the filters seems an excellent one; I'll give that a go.

juan · Sep 24, 2007

I think I would pre-wet a filter and set up the funnel so that it could drip all night if need be.
juan

Mike Wilde · Sep 24, 2007

TEA is temperature sensitive -it could freeze overnight

My TEA n the winter sits on top of a heating duct outside the darkroom door. It becomes a solid at 20C, I seem to recall.

My suggestion is to consider gently heating the solution in a double boiler, and then stir to see if you can cause the 'bits' to dissolve into solution.

I store phenidone in a 10% stock solution of prop glycol; it never fully dissolves on heating, but heating allows it to uniformly disperse into the solution. I pop the jar into the microwvae on low for a minute with the lid off, then cap it and gently shake it before syringing or pipetting off the required ammount.

aldevo · Sep 24, 2007

Well I tried a second test roll this evening using a combination of the suggestions from Mike and Ian. To be specific:

1) I heated the PC-TEA stock solution to 175 degrees and vigorously stirred it for 20 minutes before transferring it to a second glass bottle that had been meticulously cleaned
2) I pre-wet three coffee filters with distilled water and then passed the solution through each one

I also changed the final washing step whereby I used the Ilford wash method (which I otherwise don't trust) with each tank-full using distilled water.

Unfortunately, there was no change at all in the processed negatives if the initial couple scans are any indication

I don't think coffee filters will get the job done. Some research I did this afternoon revealed that these really only offer protection on the order of several tens of microns and that's one or two orders of magnitude too large.

P C Headland · Sep 25, 2007

I experimented with filtering the working solution through a coffee filter, and didn't have any problem. I got very clean negatives. I use tap water for mixing the developer, fixer and for rinsing.

I (partially) disolve the Vitamin C in a little warm to hot water, and disolve the phenidone in a small amount of warm methylated spirits (methanol). I then heat the TEA in the microwave, and stir in the two solutions. I give it a good stir, then warm it again in the microwave, then stir, and repeat until everything is disolved.

The developer lasted at least 6 months - which was how long it took me to get through my first batch - with no apparent problems.

Ian Grant · Sep 25, 2007

Regardless of the developer and its being filtered I'm not convinced that the problem lies with the developer in the first place.

For many years I processed in deep tanks, 3 of us shared the same developer and anyone using deeps tanks knows that a considerable build up of dust and other particles occurs. However this never affected any of our negatives. The fixer was similar, the important stage was the washing and drying.

It is highly likely that the particles are either in the wash water you are using, or may even be dissolved salts, if your in a hard water area, that are crystalising out as the film dries, (maybe your distilled water wash isn't sufficient), or the other alternative is dust particles as you film is drying.

You do say scans, if you are scanning the negatives fine dust particles that don't show when you make enlargements (or contact prints) become far more apparent when you scan a negative.

Ian

gainer · Sep 25, 2007

Where did you get the TEA? Are the particles in a colloidal suspension or can you see individual particles by transmitted light? What bothers me is that you could dissolve all the ingredients that are in 20 ml of PC-TEA stock in a liter of water and should not get any suspended particles, even if it contained undissolved phenidone or ascorbic acid. Anything that did not dissolve in the TEA when you made the stock should dissolve in the water of the working solution, and the worst that could happen is some minute variation in strength of the working solution if the undissolved particles are unevenly distributed in the stock.

I am perplexed. I get TEA and ascorbic acid from www.chemistrystore.com and have never had any troubles such as you describe. I get the phenidone from Photographer's Formulary.

gainer · Sep 25, 2007

Let me suggest an experiment that may point to where the problem is. Add 1/2 teaspoon ascorbic acid powder, 1/8 teaspoon phenidone and 20 ml TEA to a liter of water. This mixture should be clear and should develop most films in 8 or 9 minutes at 68 F. There should be no scum or crystals or any other foreign substance on the film when it is fixed, washed and dried. If that is true, then I do not see how the PC-TEA stock could be the cause of your problem. The problem has to be elsewhere.

aldevo · Sep 25, 2007

gainer said:
Where did you get the TEA? Are the particles in a colloidal suspension or can you see individual particles by transmitted light? What bothers me is that you could dissolve all the ingredients that are in 20 ml of PC-TEA stock in a liter of water and should not get any suspended particles, even if it contained undissolved phenidone or ascorbic acid. Anything that did not dissolve in the TEA when you made the stock should dissolve in the water of the working solution, and the worst that could happen is some minute variation in strength of the working solution if the undissolved particles are unevenly distributed in the stock.

I am perplexed. I get TEA and ascorbic acid from www.chemistrystore.com and have never had any troubles such as you describe. I get the phenidone from Photographer's Formulary.

Patrick,

- My TEA is from chemistrystore.com
- My Phenidone is from the Photographer's Formulary
- My Ascorbic Acid crystals are from NOW Foods

All containers remained very tightly sealed prior to mixing the present batch. And the same containers of chemcials used to mix the present batch of PC-TEA were used to mix its predecessor batch - which did not exhibit this trouble.

When I mixed the PC-TEA it was heated to slightly above 200 degrees. It was allowed to cool to approximately room temperature before it was decanted. During this time the Pyrex beaker was covered with plastic wrap to protect the solution from airborne particles. My eye could not detect any particles suspended in the TEA (and I did look) once it had been mixed. And I cannot detect any particles in the working solution once mixed. The particles on the processed negatives are extremely small, numerous, and appear to be evenly dispersed.

The only thing I can think of is that the Ascorbic Acid crystals from NOW must contain some impurities that are not soluble in the stock or working solutions.

Thanks for your help; it remains quite a mystery...

gainer · Sep 26, 2007

Very unlikely that it's the ascorbic acid. I have also used the ascorbic acid from NOW foods. It is after all food grade. If you try my simple recipe, using the same ascorbic acid, you will either get the same stuff on your film or not. I still think that there is nothing in the PC-TEA stock that is not soluble in water. It would also have to be insoluble in stop bath if you use it, fixer and copious wash water in order to remain on the film.

Did you try fixing an undeveloped piece of film, washing and drying it to see if it got the same particles on it?

gainer · Sep 26, 2007

BTW, you didn't mention what film you used.

aldevo · Sep 26, 2007

The film is Kodak 400TX. I use a filtered tap water stop bath. The filter was recently replaced and is of the 1-micron variety. As a side-note, I am also careful to rinse the syringes used to withdraw the PC-TEA stock from its container and I perform a final rinse in distilled water.

Yes, the Ascorbic Acid from NOW is food grade - and they claim it to be 100% pure. But I'm at least a little skeptical that any quantity of powder could be truly 100% pure.

IIRC, food grade signifies that FDA deems the substance, as manufactured and packaged, is safe for food or inclusion in food. Whether that allows for trace particle impurities that are not soluble in TEA, a solvent composed of TEA & water, or Fixer - I've no idea.

How about Phenidone? Certainly not food-grade. I believe photographic-grade is 98% purity with, obviously, restrictions on allowable impurities. My phenidone is about 2 1/2 years-old, but its container has always been sealed save when contents are withdrawn for mixing solutions. That's only happened four times.

I will try this weekend to fix and wash a piece of undeveloped film, as you have suggested.

I appreciate the help!

gainer · Sep 26, 2007

If either ascorbic acid or phenidone have impurities that are insoluble in water, they should either form a suspension or a sediment. If I use a carbonate and my well water, I get a cloudy suspension. I have done so in the past and have never had the kind of problem you report. I have used some Vitamin C with Rose hips, which also makes a cloudy solution, and have not had problems. I have crushed and dissolved ascorbic acid tablets whose binder makes a cloudy solution without problems. One thing I do that you may not. I wipe the washed negatives gently with a paper towel. I used to use a sponge squeegee, but found it hard to keep clean, while the paper towel is fresh each time. I wrap it around my fingers and use them like a squeegee. Your final rinse of distilled water may not be as distilled as it claims to be.

What I'm saying is that I have done my darnedest to cause the kind of problem you are having without success. I hope you can track it down and report it for the rest of us to be cautious about.

aldevo · Sep 27, 2007

gainer said:
If either ascorbic acid or phenidone have impurities that are insoluble in water, they should either form a suspension or a sediment. If I use a carbonate and my well water, I get a cloudy suspension. I have done so in the past and have never had the kind of problem you report. I have used some Vitamin C with Rose hips, which also makes a cloudy solution, and have not had problems. I have crushed and dissolved ascorbic acid tablets whose binder makes a cloudy solution without problems. One thing I do that you may not. I wipe the washed negatives gently with a paper towel. I used to use a sponge squeegee, but found it hard to keep clean, while the paper towel is fresh each time. I wrap it around my fingers and use them like a squeegee. Your final rinse of distilled water may not be as distilled as it claims to be.

What I'm saying is that I have done my darnedest to cause the kind of problem you are having without success. I hope you can track it down and report it for the rest of us to be cautious about.

Thanks for all the suggestions. I will report back once I've carried out some more tests along the lines of what you have proposed.

gainer · Sep 27, 2007

Here is another ploy I have used to make the solution easier. Instead of heating the TEA, mix the ascorbic acid and Phenidone dry and add an equal weight of boiling water. If you are using, say, 50 grams of ascorbic acid, use 50 ml hot water. Add the TEA as soon as the solids dissolve. The TEA will, of course, be easier to measure and pour if it is lukewarm, and impossible to pour if it is below 20 C, although it has a propensity for supercooling, but it need not be hot. The small amount of water will not affect the storage life of the stock.

aldevo · Sep 29, 2007

gainer said:
Here is another ploy I have used to make the solution easier. Instead of heating the TEA, mix the ascorbic acid and Phenidone dry and add an equal weight of boiling water. If you are using, say, 50 grams of ascorbic acid, use 50 ml hot water. Add the TEA as soon as the solids dissolve. The TEA will, of course, be easier to measure and pour if it is lukewarm, and impossible to pour if it is below 20 C, although it has a propensity for supercooling, but it need not be hot. The small amount of water will not affect the storage life of the stock.

Well, guess what? It isn't the developer at all...

In looking at the scans it occurred to me that the spots are a bit too light (dark on the negative) to be invisible when present in developer solution in a clear beaker.

I checked the camera used to shoot the negs and it it's evident that the recent CLA given to the camera failed to replace some of the foam rubber light seal above the pressure plate. Rubbing my finger lightly across that area of old foam rubber caused it to crumble into granules.

It seems that I was the victim of a camera tech who thought he could save a bit of time at my expense and my own inability to remember that film, generally, resides in a camera at some point prior to its processing! To quote an old Dr. Who episode "First things first, but not necessarily in that order!"

Sorry to have wasted your time, Patrick. There's lots of good stuff here that you've posted, though, which should help somebody debug this sort of problem in the future.

Ian Grant · Sep 30, 2007

You owe me a pint
"Regardless of the developer and its being filtered I'm not convinced that the problem lies with the developer in the first place."

Ian

aldevo said:
Well, guess what? It isn't the developer at all...

In looking at the scans it occurred to me that the spots are a bit too light (dark on the negative) to be invisible when present in developer solution in a clear beaker.

gainer · Sep 30, 2007

Don't feel bad. No one wastes any more of my time than I do, and it's not a waste anyway to try to help someone. Glad you found the problem. The hint about mixing at lower temperature is a good one, though. TEA gets dark with high heat, and even though it works fine, it worries some a lot.

Need help with filtering PC-TEA

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