Isolation of Tannic Acid from bark

[htmlguru4242]

I know that tannic acid / gallic acid developers were used the past for developing film (pyrogallol is, obviously, still used today).

Does anyone know how to isolate tannic acid from the bark / nutgalls of oak trees? I have a lot of oak trees around and gallic and tannic acids are expensive to purchase commercially ...

Any ideas how to do this?

 

[noseoil]

I wouldn't try to re-invent the wheel. Once you have isolated the tannin, you still have to come up with a formula to work with it in a developer. Photographer's formulary sells PMK pyro kits, or for that matter, pyrocat, both of which are superior developers.

Seems to me you would be spending more time in rendering the oak galls than in taking pctures and developing them. Why set up a lab when the finished product is in no danger of going away commercially? tim

 

[htmlguru4242]

I see what you mean here, though I think that it would be a neat exercise; I live playing around with chemistry, to me, it's an interesting process to make developers.

 

[Photo Engineer]

Dry acorns, grind them and boil in water. Save the water and filter out the solids.

The water can be concentrated by gentle heating to get tanins.

PE

 

[htmlguru4242]

Ah, thank you, PE, I'll try that, though I didn't realize that it was so simple ...

What should I be looking for as far as a basic formula for a develoepr after this?

 

[Donald Qualls]

I'd start with one of the old gallic acid formulae from the 1870s-1880s. Google for developers for use on dry plates, you should find what you want. What you get by evaporating acorn tea will be of low purity relative to gallic acid, so you'll probably have to use a good bit more of it than those formulae call out.

BTW, you can also extract tannins from black tea, though I don't know if the yield is high enough to be worth paying for the tea (even at only a couple cents a bag) compared to picking up acorns in the park (or your front yard).

 

[Photo Engineer]

BTW, that reminds me.

The acorns, once boiled free of tannins can be dried, shelled and ground to make a flour for breads and cakes that is supposedly quite tasty. At least the Native Americans thought that to be so.

They served it with venison stewed in maple syrup. At least that is according to one menu that I read years ago. Spices included 'greenstick' or sassafrass.

PE

 

[Kino]

You can also leach tannic acid directly from the leaves of oak trees. Take a wooden barrel, fill with leaves, and acorns and pour boiling water over the leaves. Let the it steep for a week or so and decant. Boil down gently with good ventilation) for higher concentration of acid.

The tip about the eating the acorns are true; you can make some interesting pancakes from acorn flower and they are good to munch on after 3 changes of boiling water and "candied" with melted sugar.

 

[Kirk Keyes]

Ah, thank you, PE, I'll try that, though I didn't realize that it was so simple ...

What should I be looking for as far as a basic formula for a develoepr after this?

Are you trying to make pyrogallic acid from the tannins? If so, you need to first fermant the oak galls and let them mold, and then extract them with water saturated ether and then carefully dry the extract. It's very flammable!

Heat the tannin extract with either strong acid or base to make gallic acid. Then you need to heat the gallic acid with 3 times its weight of water in an autoclave to make pyrogallic acid. (According to my Hawley's Condensed Chemical Dictionary.)

Actually, I've seen an online reference to an old photo manual from around the 1880s that has really nice descriptions of how to prepare chemicals like this from basic materials. Perhaps someone else here knows the reference and can link to it for us?

If you are looking for tannic acid, it is actually realatively cheap commercially. 100g for $30 at Photographers Formulary, and 1 lb for $49 at Artcraft Chemicals.

Anyway, I've played around with using tannic acid as a developer - at least a couple of tries to see how feasable it is. It works. It actually stains pretty nicely too. Visually (and that's all the further I've taken it) it's similar to Pyrocat HD. I can't find my notes at this point, but try substituting tannic acid for pyrocatechol in the Pyrocat formula, but use 5 or 10 times more tannic acid for a start. Using a formula like this, I processed some FP4+ for 10 minutes by tray at about 25C and I got a visual CI of 0.66 and a blue CI of 0.73. The base+fog was nice and low - 0.11 and 0.12 respectively.

So it does work. I was intruiged by the idea that tannic acids, while similar to pyrogallol and pyrocatechol, are a much larger molecule. THat should have an affect on a couple of different areas that I could think of. Safety and the physical action of the developer.

Tannic acid is not one specific compound, but rather, a mixture of very closely related compounds. They usually have a molecular weight of around 2000 AMU and it is often given a molecular formula of C76H52O46. Or I should say group of molecules. They used to be classed as glucosides as they have sugars that hold the componants of the tannins together via esters, but nowadays they are considered a class of chemicals on their own right - tannins are now classed as a polyphenolic compound. And that is what related them to compounds used in "pyro"-type staining developers. Think of the biggest, hairyist molecule you could make by linking together dozens of pyrocatechol and pyrogallol molecules, with all the -OH functional groups hanging out into space to do their magic on all your AgX crystals in the film. And even though it is such a large molecule, tannic acid is very soluble in water, so making the developer is not going to be an issue. (One thing I've noticed is that tannic acid usually dissolves incompletely - even though it is very soluble in water, there are still some dregs left behind - about 1% maybe. I suggest you filter the solution before you actually try using it on some non-test images.)

The other thing I thought interesting was that if the molecular size of tannic acid is so large, then that may help make it a "safer" staining developer. It should be less absorbed by your skin. And the MSDS data bears this suspicion out.

While tannic acid has a Health Rating of "2 - Moderate", it actually has a Contact Rating of "1 - Slight" and is said to be only a "Mild Irritant". It is neither a known or anticipated carcinogen. See: http://www.jtbaker.com/msds/englishhtml/t0065.htm

Compare this with pyrogallol having both a Health and Contact Rating of "2 - Moderate" and it is listed as a skin "Irritant". See: http://www.jtbaker.com/msds/englishhtml/P7973.htm

Pyrocatechol is has a Health and Contact Rating of "3 - Severe", and is listed as "Corrosive" under Skin Contact. See: http://www.jtbaker.com/msds/englishhtml/P7896.htm

Of course, those listing are for the dry powders, but these properties will probably be reflected the these compounds while in solution.

So tannic acid is significantly less hazardous by skin contact. And I know we all try to use gloves when handling our developers these days, I'm sure there are still some people out there that use bare skin when developing by tray. So I was thinking that a tannic acid developer would greatly reduce the risks associated with this practise. (Tannic acid also has a lower Oral LD50 than either pyrogallol or pyrocatechin, but this advantage may be lost by having to use more of it in the developer since tannic acid seems from my few tests to be a little less active.)

And the last thing I thought interesting about trying a tannic acid based developer is that it may not penetrate very deeply into the emulsion - as I said, it is considered to have a molecular weigth of around 2000 AMU. That's huge compared to most other developer compounds. It seems to me that it will inhibit transport deep into the emulsion. And I'm guessing it will bind to the gelatin in the emulsion with all those -OH functional groups hanging off of it. I suppose that's why James and Mees list tannic acid as one of the strongest staining developer agents (ahead of pyrocatechol but behind pyrogallol), so that seems like an another reason to try this.

Anyway - I would skip ahead from making some tannic acid and buying some for yourself and try a few developer fomulas with it. I think it holds a lot of promise, both from a staining viewpoint, as well as a safety one as well.

For something simple, try a PMK based formula but with 5 times more tannic acid than pyrogallol for starters.

Let me know what you find!

Kirk - www.keyesphoto.com

 

[Donald Qualls]

If you are looking for tannic acid, it is actually realatively cheap commercially. 100g for $30 at Photographers Formulary, and 1 lb for $49 at Artcraft Chemicals.

Ummm. Your definition of cheap doesn't match mine, or likely that of htmlguru either (he's in college, last I checked). Formulary has Metol for about 1/4 that price (a pound is barely more than 100 g of tannic acid), which IMO doesn't put tannic acid in the "cheap" category. The Artcraft price is closer to reasonable, and there are probably other suppliers who can beat that.

And I suspect part of the idea here is related to the "making photo chemicals from common materials" meme -- making developer from acorns has a lot more cachet, even if the resulting developer is inconsistent, than making it from technical grade tannic acid that arrives in a plastic bottle. Heck, I've got enough acorns in the yard that this tempts me (though I might have missed out for this season, since the squirrels have probably long since collected the good ones).

BTW, you can extract tannins from oak bark, too, just as from the leaves. There are manys streams in the northeastern United States that look like tea as they flow in their beds, due to tannins picked up from oak roots and leaves. I'm guessing those aren't popular to drink from...

 

[Photo Engineer]

BTW, you can extract tannins from oak bark, too, just as from the leaves. There are manys streams in the northeastern United States that look like tea as they flow in their beds, due to tannins picked up from oak roots and leaves. I'm guessing those aren't popular to drink from...

Donald;

I don't like the idea of extracting tannins from oak bark as it can be more destructive to the living tree. Using leaves or acorns is much better, and in the case of acorns can yield a tasty food.

Just watch out for acorns with holes. They have worms.

PE

 

[htmlguru4242]

I do agree with not removing the bark, though if I find a felled tree, it's not too bad to take the bark

I do have a few gallon freezer bags full of acorns from about a year ago when they were collected (who knows why), so perhaps those will be useful.

Someone mentioned fermenting the oak galls ... how is this accomplished? And I'm assuming that acorns could be used instead / as well?

 

[Kirk Keyes]

Someone mentioned fermenting the oak galls ... how is this accomplished? And I'm assuming that acorns could be used instead / as well?

I think that was me. I'm not sure acorns would be a suitable substitute for galls. They are not the same.

Galls are irregular plant growths which are stimulated by the reaction between plant hormones and powerful growth regulating chemicals produced by some insects or mites. Galls may occur on leaves, bark, flowers, buds, acorns, or roots. Leaf and twig galls are most noticeable. The inhabitant gains its nutrients from the inner gall tissue. From: http://www.uky.edu/Ag/Entomology/entfacts/trees/ef408.htm

My understanding is that any plant material will release tannins as the material decomposes, but there are some things, like the galls, that are higher in tannins and that's why those sources were preferable.

As to the definition of inexpensive, I go by the motto, "Time is Money". If it takes me a lot of time to accomplish something that I could have just gone out and bought, then I see that as a possible bad use of my time. And the money it took to use that time...

But I too remember those days in college, like when we tried to make rocket engines from a couple pounds of ammonium nitrate fertilizer and suger, or the time we made SCUBA diving weights from a gallon bucket full of wheel-balancing weights. (I actually still use the diving weights for things like keeping the Xmas tree from falling over, or light stands. I think I've almost recovered the time expense from that project after 20 years.)

 

[Kirk Keyes]

how is this accomplished?

Oh yeah - I almost forgot. I think you simply soak the galls in water and cover them and then let them sit. They will start to mold eventually. I suspect the mold helps to break down the lignin in the woody material and release the tannins.

 

[Richard Wasserman]

If you can find a copy of "The Silver Sunbeam" by J. Towler 1864 (it was reprinted in 1969 by Morgan and Morgan) there are complete directions for making Tannic Acid from oak galls using ether. You can also make gallic acid from decomposed and moldy nut galls, but his takes about 3 months for everything to get good and moldy. The gallic acid can then be made into pyrogallol by heating it in oil This evidently was the best method in the 1860's and was widely used. I suppose I could copy the instructions if anyone is interested. This book is a very interesting look at the state of the art of photography in it's early years. Boy, do we have it easy!

Richard Wasserman

 

[Kirk Keyes]

If you can find a copy of "The Silver Sunbeam" by J. Towler 1864

THAT'S IT! The book I mentioned earlier. No need to scan it, it has already been done. See: http://albumen.stanford.edu/library/monographs/sunbeam/

 

[Photo Engineer]

Oak leaf galls are little balls or bubble like structures, usually found at the base of the leaf where it joins the stem. It is caused by an 'infecton' of the leaf stem. If you squeeze them, they pop. They usually appear to be empty, but there are small 'thingies' living in them.

PE

 

[htmlguru4242]

OHH - that's where that is; I knew that there was some old photo manual out there, but not what or where. That is good to know; their idea about using ether for tannin extraction sounds good.

Now just to find the ether - I'm imagining that that won't be a hardware store find ... does anybody here in the US know of where to get ether other than a chem. supplier?

 

[Photo Engineer]

Be very careful. I have been involved in more than one explosion with ether. It is very flammable and dangerous. If it is kept on the shelf too long, it forms peroxides which can explode just by moving the container.

The vapor travels for dozens of feet remaining flammable and liable to explosion and that is what caught me unaware. I was carrying a beaker of ether past a hotplate (about 5 ft away in a hood) and the draft from the hood drew the ether vapor across the surface of the hotplate igniting it and causing an explosion. Friends told me I was surrounded by a blue flash of light like an aura, and I lost a lot of hair including eyebrows. From my standpoint it looked like a flashbulb had gone off and I felt a burning sensation over all of my exposed skin. I was lucky!

PE

 

[htmlguru4242]

Ah, i realized that tehre were dangers, but I didn't realize that much. These experiments will probably be conducted out of doors, so I have the ultimate ventilation ...

 

[Kirk Keyes]

Now just to find the ether - I'm imagining that that won't be a hardware store find ... does anybody here in the US know of where to get ether other than a chem. supplier?

Most chemical supply places will think you are making illegal drugs if you ask for ether. SO I suggest you go, not to the hardware store, but the auto parts store. Look for "starting fluid" - it's usually ether. Check the label for "diethyl ether".

It is very flammable. And it has narcotic properties. So be careful!See:http://www.jtbaker.com/msds/englishhtml/E2340.htm

 

[Kirk Keyes]

The vapor travels for dozens of feet remaining flammable and liable to explosion and that is what caught me unaware. I was carrying a beaker of ether past a hotplate (about 5 ft away in a hood) and the draft from the hood drew the ether vapor across the surface of the hotplate igniting it and causing an explosion. Friends told me I was surrounded by a blue flash of light like an aura, and I lost a lot of hair including eyebrows. From my standpoint it looked like a flashbulb had gone off and I felt a burning sensation over all of my exposed skin. I was lucky!

WOW! You were lucky. That's a great story.

I never have cool lab accidents like that (fingers crossed). Last thing I did was break off a pastuer pipette that was in some partially digested manure compost leachate and then ram the glass into the end of my thumb. 6 stiches... and a tetanus shot.

 

[htmlguru4242]

Last thing I did was break off a pastuer pipette that was in some partially digested manure compost leachate and then ram the glass into the end of my thumb. 6 stiches... and a tetanus shot.

Oops ... broken Pasteur pipes can be surprisingly sharp ... and manure leachate ...


I didn't realize about the starting fluid, I'll check on that.

 

[Photo Engineer]

One day, I was entering the lab and was pushing open the stainless steel safety door when I felt a 'thud' and something hit the door and knocked it back at me nearly hitting my face.

I went forward again and the door bottom scraped on broken glass on the floor. I walked in to find a broken high pressure hydrogenation bottle lying on the floor, and there was about a 2" deep depression in the door at waist height.

It seems that the HP hydrogenator blew up just as I was walking in the door. The explosion was such that it destroyed the safety cage around the bottle, but did not disturb anything to the sides or behind the apparatus. It was all directed one way, towards the door, just like a shaped charge. If I had been about 1 second earlier, I would have probably not survived. Nothing was harmed except for the safety cage, bottle and door (which was only dented). I do believe in miracles!

Neither this nor the incident above happened at EK. These were both in graduate school.

PE

 

[Mark G MacKenzie]

Ether Flash

Hi. Fascinating reading. My own profession (art conservation) has used ether for a variety of treatments in the past. We were always warned that diethyl ether has a flame trail or flash back capability of nearly 35 feet. That is an open flame or ignition source 35 feet away from an open can of ether will cause it to ignite. Kind of scary.

Some of the early treatments involved refluxing archaeological artefacts in a bath of boiling/distilling ether. In glass no less.

Well, back to setting up my wet plate equipment/chemicals.

Mark MacKenzie