PC-TEA suggestions

[thomsonrc]

HI,

I have just ordered some TEA with the intention of making PC-TEA, but there a couple of things I am wondering about having looked at old threads on this developer.

1. Patrick Gainer posted in 2005 saying that it can be made with water to avoid heating the TEA, but in the just released edition of the Darkroom Cookbook the recipe is the original without water. Does anyone know if there were keeping problems with the water version?

2. There was a thread stating that PC-TEA caused increased fog and suggesting additives, but only 3 people commented on this. Is it really a problem?

3. any tips on making or using it?


Cheers

Ritchie

 

[ntenny]

Hi Ritchie,

I did the same thing a few months ago, and found that my level of worry was way out of proportion to the actual difficulties. I had the same worry about fog, but I haven't found it to be a problem at all.

What I found unexpectedly useful was a little water heater intended for warming baby bottles (an electric kettle with a thermostat would work as well). With something like that, it's quite easy to keep the temperature of the TEA up without resorting to the microwave. I dissolved my phenidone in propylene glycol in the interests of preserving it, so I haven't had to worry about the phenidone dissolving in the TEA, but raising the temperature helps a lot with dissolving the vitamin C.

That said, I still always add the vitamin C too fast and end up with some clumps on the bottom. They reduce over time and can be stirred in a bit if I heat up the jar again. Someone more patient could probably get it all stirred in nicely to start with.

I would assume that a version in water wouldn't keep well---as I understand it, the point of using organic solvents like TEA is to keep water away from the P and C.

I really like this stuff; it's pretty much become my everyday developer.

-NT

 

[gainer]

The ruckus about using the microwave had to do with the flashpoint of TEA. Flashpoint occurs generally below the boiling point and is the emperature at which the partial pressure of the TEA is great enough the be ignitable by an open flame. Now, if you cover the containing vessel with microwave-safe plastic wrap such as Glad Wrap, so that the plastic is slack in the center and is tightly sealed at the edges, the TEA will have to be above its boiling point in order for the plastic to rise. That point is much, much higher than the flashpoint. At the flashpoint, the vapor pressure will not be high enough to lift the plastic, so there will be no contact between vapor and the imagined open flame.

Phenidone in the amount required is easily soluble in TEA. 90 grams of ascorbic acid per liter are sufficient. Once it is dissolved, it can be stored at room temperature. The difficulty with dissolving is caused by lower molecular motion, and cold TEA is quite viscous to boot. Heating reduces viscosity and vigorous stirring replaces molecular motion.

TEA is, of course, a fairly strong base when dissolved in water.

 

[martyryan]

Concerning point 2, I am one of the few people that seem to have a problem with increased base fog, .5 to .6 grams of potassium bromide per liter has solved the problem for me

Marty

 

[Murray Kelly]

Concerning point 2, I am one of the few people that seem to have a problem with increased base fog, .5 to .6 grams of potassium bromide per liter has solved the problem for me

Marty

I was reading-up about latensification the other day and it was along the lines of 'wash the film in a weak ammionia in isopropyl alcohol and dry'. It was more of a hypersensitivity they wanted.

So following that up in google there was another reference to triethanolamine being used for the same purpose. I couldn't get any further with that one - only a short one liner almost, in a rambling patent description. It all left me wondering if the TEA is more than a solvent and alkaline pH supplier for the developing agent (phenidone in this case)?

Could it be an active latensifier which I have never seen discussed and doing more than one might be led to think?

It might explain the fogging somehow. Do you 'flash' your films or something? The extra latensification of TEA, if it exists, might be pushing the film into the fog range.

Just a thought.

Murray

 

[thomsonrc]

The ruckus about using the microwave had to do with the flashpoint of TEA. Flashpoint occurs generally below the boiling point and is the emperature at which the partial pressure of the TEA is great enough the be ignitable by an open flame. Now, if you cover the containing vessel with microwave-safe plastic wrap such as Glad Wrap, so that the plastic is slack in the center and is tightly sealed at the edges, the TEA will have to be above its boiling point in order for the plastic to rise. That point is much, much higher than the flashpoint. At the flashpoint, the vapor pressure will not be high enough to lift the plastic, so there will be no contact between vapor and the imagined open flame.

Phenidone in the amount required is easily soluble in TEA. 90 grams of ascorbic acid per liter are sufficient. Once it is dissolved, it can be stored at room temperature. The difficulty with dissolving is caused by lower molecular motion, and cold TEA is quite viscous to boot. Heating reduces viscosity and vigorous stirring replaces molecular motion.

TEA is, of course, a fairly strong base when dissolved in water.

Thanks for your comments, from which I take it that if I follow the 'clingfilm' method its as safe as using the water method and it will last longer. Have you ever noticed any 'fog' problems Mr Gainer?

 

[gainer]

The fog problems I have had were attributable to the film I was using. I presume you are not referring to base density of some 35 mm films that is used to prevent or minimize light piping through the tongue, and in some cases to minimize halation. The base density of HP5+ 35 mm is greater than either HP5+ 120 or sheet film.

You could test the TEA latensification hypothesis by mixing some PC-Glycol and using a metaborate activator solution as is used with PMK.

HP5+ is usually not a high contrast film. Any effort to get a CI greater than 0.6 by extended development is likely to produce more fog than contrast. It may seem contrary to intuition, but increasing the concentration of PC-TEA to 1+25 may get the contrast you want with less fog. It works that way with Rodinal.

 

[P C Headland]

I've mixed up a few batches of PC-TEA now. I find it easiest to disolve the phenidone in some alcohol (methylated spirits), and the vitamin C in some water. I then heat the TEA in the microwave so it is "warm tea hot", then mix the phenidone solution, then add the vitamin C solution.

I've not had any problems with longevity, or noticed any other ill effects from doing it this way. Adding phenidone powder to the TEA required a lot of stirring and keeping the TEA warm....