Triethanolamine (TEA) -- What does it actually do?

So I've used a lot of TEA, it's kind of a wonder chemical in my mind. However, I'm not 100% sure of everything it actually does. Things I've seen claimed:

* Silver solvent (but how much of a solvent compared to sulfite?)
* Alkali / pH buffer (best for pH of ~10 depending on dilution)
* Chelating agent (makes shelf life better according to one researcher?)
* Sensitizing agent (ie, used in emulsion making for initial sensitization)
* Hypersensitizing agent (often used in holography, but also in some astronomy use cases)
* Preservant solvent for developer formulas (contains no water and capable of dissolving most developing agents without oxidizing them)

I've personally witnessed a lot of weird stuff with TEA concoctions. TEA in presence of excess sodium chloride or potassium iodide in developer will stain prints yellow. As a prebath TEA in presence of potassium bromide will chemically fog ortho litho emulsions and will chemically reduce speed and blacks of some RC paper emulsions. I'm talking about fairly dilute amounts too, less than 10ml per L of solution. I've also heard that it has some weird effects when used in fixer (Kodak didn't like it apparently?) and TEA or similar is an often essential ingredient in color developers, but without any good explanation I've seen. TEA is of course a solvent capable of dissolving most developing agents and making a shelf-stable solution, but honestly there seem to be very few formulas which make use of that property. (though some notable ones like PC-TEA)

I'm trying to understand this chemical more and it's rather baffling. It comes up a lot in patents and papers (or other similar -amines) but without any great explanation why it's used specifically. It seems like the silver solvent effect is rarely used and indeed despite HC-110 being quite TEA heavy, it is not considered a particularly fine grain developer. The alkali buffer effect is used some, but honestly less than I would've expected (typically both TEA and another alkali is present in formulas). Chelating agent effect is only used by one researcher as far as I can tell. It's very often used for sensitization and hypersensitization.

Can anyone help me understand why TEA is often used in very dilute amounts in various developers, especially color developers?

not being the "mix-it-yourself" type, using only manufactured chemicals, i found your question and discussion interesting and lucid. Almost makes me want to run out and get some scales and TEA! thanx.

Puts me in mind of Pat Gainer who said that when he espoused spoon measurements one of his friends went out and bought some scales.

Add to your list TEA is also a copper getter. Copper in water can cause havoc with some organo-chemicals in color work.

earlz said:

and TEA or similar is an often essential ingredient in color developers, but without any good explanation I've seen.

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I have not yet seen an established color developer formula in which TEA is used. Some E-6 CD formulas use Ethylenediamine. Is this what you meant with "TEA or similar" ?

Rudeofus said:

I have not yet seen an established color developer formula in which TEA is used

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It's commonly present in RA4 developer. So far I have always assumed it played a role in pH buffering, but maybe there's more to it.

I'm following this thread with interest; so far I was aware of the use of TEA as a solvent for concentrates and as a pH buffer in working solutions, but e.g. its use as a chelating agent or sensitizing agent is something I did not know.

I'm also kind of surprised concerning the remark of its use (or lack thereof) in fixer, as it doesn't seem like a particularly likely candidate for a fixer ingredient, especially since most commercial fixers are acidic.

Jacobson & Jacobson discuss the use of TEA in hyper-sensitising film and plate. They recommend a two minutes bath in 0.5% solution of TEA at 55°F. The reason they give for hyper-sensitising property of TEA is that it removes slight excess of potassium bromide present in emulsions. They say bromide helps in keeping fog low but slows down the film. The sensitising bath removes bromide and increases speed. It needs to be done before the exposure.

TEA seems to be a chelating agent, and helps create complex Ag molecules
It is used in the fabrication of Ag nano particles and to help deposit pure forms of silver and silver oxide/peroxide

I don;t know the role in the developer, but form what I read it will be a developer agent (reducer) as well as a solvent to keep the grain small

titrisol said:

TEA seems to be a chelating agent, and helps create complex Ag molecules

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It is indeed a weak silver solvent (read: it will fix Silver Chloride), but when people refer to its chelating property, they mean Copper. Copper, like Iron, is a common impurity in tap water and many chemical ingredients used in photo chemistry, and it accelerates decomposition of many development agents in solution. Ryuji Suzuki used TEA (binds Copper ions) and Salicylic Acid (binds Iron ions) to keep this under control.

titrisol said:

I don;t know the role in the developer, but form what I read it will be a developer agent (reducer) as well as a solvent to keep the grain small

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TEA is not a known development agent. It is a weak silver solvent, and if used correctly, it may reduce graininess.

Here is a formula containing TEA believed close to Agfa Studinol or Rodinal Special:
http://photoclub.od.ua/viewtopic.php?f=38&t=1634
While it might be possible to replace the TEA by sodium bicarbonate as an alkali, TEA has also the property of being a silver solvent, a rather unique property combination at this pH.

Mostly, it is just a liquid alkali useful for making liquid kits! The solvent action for Silver Halide that is attributed to it is generally due to impurities such as DEA. It is a very weak solvent and a very weak chelating agent. It is very good for making water free liquid kits such as HC110.

PE

Raghu Kuvempunagar said:

Jacobson & Jacobson discuss the use of TEA in hyper-sensitising film and plate. They recommend a two minutes bath in 0.5% solution of TEA at 55°F. The reason they give for hyper-sensitising property of TEA is that it removes slight excess of potassium bromide present in emulsions. They say bromide helps in keeping fog low but slows down the film. The sensitising bath removes bromide and increases speed. It needs to be done before the exposure.

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I find that rather interesting. One of my most "weird" uses of TEA is "PFS-4", a dilute TEA+bromide prebath done just before development for ortho litho films which will increase the shadow speed of the film by several stops as well as soften the extreme toe typical with a lith emulsion, though also has a tendency to fog the film. It only has any real effect on ortho litho films though and is quite sensitive to the grade of TEA that is used (yellow easily frozen grade will add ~1/2-1 stop more than clear harder to freeze grade)

Alan Johnson said:

Here is a formula containing TEA believed close to Agfa Studinol or Rodinal Special:
http://photoclub.od.ua/viewtopic.php?f=38&t=1634
While it might be possible to replace the TEA by sodium bicarbonate as an alkali, TEA has also the property of being a silver solvent, a rather unique property combination at this pH.

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If that's the case, why not use sodium sulfite though?

Many people mistake the solvent capacity of TEA to impurities with rather "bad" TEA.

PE

Photo Engineer said:

Many people mistake the solvent capacity of TEA to impurities with rather "bad" TEA.

PE

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How can one actually judge the quality of their TEA? I bought some from some art supply type place that was yellow and froze easily. The stuff I have from FPP is clear and will not freeze as easily. I always assumed FPP provided photo grade 99% TEA, but maybe I'm wrong about that

Edit: at least according to the SDS the FPP provides, it matches up to >= 99% purity and/or "gas chromatography" (GC) grade? Honestly looking at the prices at sigma I don't see how FPP provides TEA for so much cheaper. Direct prices are over double what FPP's are. I'd assume they don't dilute their solution or anything like that

Here are product descriptions for 4 types:
http://msdssearch.dow.com/Published...fety/pdfs/noreg/233-00267.pdf&fromPage=GetDoc
I had 99% from ebay,

Try here: https://en.wikipedia.org/wiki/Triethanolamine

TEA visually looks like water and pours like honey. It becomes a solid at about 20C or 70F. If it does not crystallize at that temperature, and/or is colored, it is not pure.

It is odorless.

PE

Photo Engineer said:

Try here: https://en.wikipedia.org/wiki/Triethanolamine

TEA visually looks like water and pours like honey. It becomes a solid at about 20C or 70F. If it does not crystallize at that temperature, and/or is colored, it is not pure.

It is odorless.

PE

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I have all of those properties except for the melting point. My basement where I keep it varies from 68-74F and I’ve yet to have this batch of TEA crystallize. Maybe the less pure batch I has just has a higher melting point by a few degrees and thus can freeze at my basements room temp. If impure grades can be up to 15% DEA and DEA has a melting point of 83F then I suppose that would make sense. Also wonder if air pressure can make a significant difference. Elevation of my house is 6000ft. Either way I’ll stick with my assumption that FPP is pure enough for my purposes and one of the cheapest sources for it

If you look in the references, there are mixtures that melt and pour differently. This is why the references list different quality products.

PE

earlz said:

I have all of those properties except for the melting point. My basement where I keep it varies from 68-74F and I’ve yet to have this batch of TEA crystallize. Maybe the less pure batch I has just has a higher melting point by a few degrees and thus can freeze at my basements room temp. If impure grades can be up to 15% DEA and DEA has a melting point of 83F then I suppose that would make sense. Also wonder if air pressure can make a significant difference. Elevation of my house is 6000ft. Either way I’ll stick with my assumption that FPP is pure enough for my purposes and one of the cheapest sources for it

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Triethanolamine is very hygroscopic, meaning it will readily absorb water from the atmosphere. It probably doesn't take much water content to significantly alter the melting point.

One interesting additional property I found for TEA is that it can function as an antioxidant for "animal fats", ie, preservative for foodish things or something? I wonder if any of these antioxidant properties can extend to developing agents.

Chemical Book says melting Point is 21.2C (69-70F) so you are in the range of solidifcation at 68-74F
https://www.chemicalbook.com/ChemicalProductProperty_EN_CB9852620.htm

earlz said:

I have all of those properties except for the melting point. My basement where I keep it varies from 68-74F and I’ve yet to have this batch of TEA crystallize. Maybe the less pure batch I has just has a higher melting point by a few degrees and thus can freeze at my basements room temp. If impure grades can be up to 15% DEA and DEA has a melting point of 83F then I suppose that would make sense. Also wonder if air pressure can make a significant difference. Elevation of my house is 6000ft. Either way I’ll stick with my assumption that FPP is pure enough for my purposes and one of the cheapest sources for it

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Raghu Kuvempunagar said:

Jacobson & Jacobson discuss the use of TEA in hyper-sensitising film and plate. They recommend a two minutes bath in 0.5% solution of TEA at 55°F. The reason they give for hyper-sensitising property of TEA is that it removes slight excess of potassium bromide present in emulsions. They say bromide helps in keeping fog low but slows down the film. The sensitising bath removes bromide and increases speed. It needs to be done before the exposure.

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I can’t believe how quickly this thread stopped and the seeming apathy, or at least disinterest towards the whopper of relatively easy hypering with TEA.

Several questions arise:

How is it best performed?

Is it combinable with other kinds of hypering, like hydrogen hypering?

Is it “only” applicable to B&W film?

There are several papers on the web about using TEA on holography stock. Are the basic techniques the same for all film?

What is this Jacobson & Jacobson book you speak of?

Helge said:

What is this Jacobson & Jacobson book you speak of?

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https://archive.org/details/developingnegati17jaco/page/n251/mode/2up

Just an update to further findings with TEA. It definitely is such a weak silver solvent that a formula I made, EXG1, is a rodinal-style coarse grain developer despite having ~20ml/L of TEA. Also, TEA has some interesting chemical properties in developers, especially with hydroquinone. I once mixed 1g of hydroquinone with 100ml of TEA and topped it to 500ml with water. Despite being quite alkaline and even the developer quickly going mud brown, it continued to be an effective developer for over 24 hours, something unheard of for a hydroquinone developer with no sulfite. Also, unlike a typical hydroquinone no/low sulfite developer, there was absolutely no infectious development when I diluted it a bit further, added some carbonate and bromide and used it as a paper developer (with the solution that sat for 24 hours). It produced a rather boring neutral tone print without deep blacks. I believe this action is because hydroquinone decays into radicals and peroxide, both of which go on to accelerate auto-decay of the remaining hydroquinone in solution. The TEA kept these reactions from happening and so I guess hydroquinone became a much more stable developing agent as a result, maybe similar to glycin or something else that can actually last more than a few hours with no sulfite.

Also TEA and alcohols I've found to affect the diffusion of developer into emulsion layers. I believe this may be the reason for either to be used in color developers. I believe TEA increases diffusion into lower color layers and alcohol actually decreases it, but I may be wrong about that. I don't exactly have a good method of testing this precisely

As for hypersensitization action. I recall seeing reports that it works with Acros (the old stuff) but the biggest problem was it removed the antihalation layer. The film also needed to be dried and used within 2 hours or so as the hypersensitization effect faded quickly. I have no idea how this actually works. I haven't seen any real documentation or explanation as to how hypersensitization by any method works though, including the old, dangerous, and apparently more effective mercury vapor method. All of the methods required quick working though and the effect faded within a few hours. The only idea I have is that similar to making silver bromide etc, maybe these hypersensitization methods create an unstable silver complex that is also sensitive to light, to a further extent than the typical silver bromide/chloride etc. The silver complex must decay into something either not light sensitive or breaks off from the silver so that it creates fog.

I've never heard of hypersensitization being used for color films honestly. I expect that you'd have color balance problems though due to unbalanced speed increases across the color layers.

TEA seems to be often used for holography for aspects not really applicable to normal photography. Things like more distinct etching and such that matter for holography viewing but make no real difference with scanning or printing. Also holography emulsions are quite different from traditional photography emulsions, even if they are both backed by similar chemistry.

Oh, hypering was indeed used for colour. Both slide and negative. And with great success.

You always hear the same platitudes, about hypering not working on modern emulsions (I can see where at least one of them probably originates with the J.& J. book), or only making a very small difference.
Or that it is only worthwhile for long exposures to compensate for reciprocity failure, giving only modest speed increases with normal exposure times.
That might be correct.
But:
A. A small difference of one or a few stops can also be very useful, especially if you are pushing film and are looking for lifting of the shadows.
B. Two or more techniques can be combined, for a more dramatic difference.
That is possible because the hypering works on different parts of the physical processes in the emulsion.

For example, combining pre-flashing (or concurrent flashing (CPA)) and hydrogen hypering can result in a far faster film.

Where you would have a gotten very high contrast and crushed shadows, if you pushed the film to 1600 or 3200 and large grain too, without any special treatment, you instead get results that are not a lot different from the base 400 speed.

Helge said:

A. A small difference of one or a few stops can also be very useful, especially if you are pushing film and are looking for lifting of the shadows.
B. Two or more techniques can be combined, for a more dramatic difference.
That is possible because the hypering works on different parts of the physical processes in the emulsion.

For example, combining pre-flashing (or concurrent flashing (CPA)) and hydrogen hypering can result in a far faster film.

Where you would have a gotten very high contrast and crushed shadows, if you pushed the film to 1600 or 3200 and large grain too, without any special treatment, you instead get results that are not a lot different from the base 400 speed.

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Have you gotten these results, or do you just think you'd get them based on your theory. Call the advice handed out by knowledgeable people here "platitudes" all you want, maybe these folks actually know a thing or two.

Looking forward to seeing great results from you with TMY @ EI6400. Can't be that hard, can it?

PS: I am aware of Dan Lee's promising results with preflashing, and realistically that's the best you'll get. Good luck proving us all wrong.