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Mammoth tooth stabilization


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Hello everybody,

 

So, a friend of mine gifted me a mammoth molar he's had for sometime now (he's not into fossils, got it himself from somebody else). The molar was found a long time ago, is as it was found (not stabilized), and in 3 pieces. 2 of them fit nicely together, one seems to be missing some smaller bits but could still go glued together. The molar itself is pretty stable, while there are occasional exterior pieces falling it is not a very fast degradation, but still, i would like to stabilize it. Somebody gave me a quick hint that i could use epoxy to glue the pieces together and then soak the mammoth molar into a solution of watered PVA glue, so that i can get into every hole and stop the degradation process. 

 

I was hoping some of you guys might give me a bit of a more detailed approach to this. Mostly, i am interested what is the ratio between the PVA glue and the water in the watered PVA glue solution and how much should i leave it soaked in it. Also, in case you guys know of an alternative stabilization method i am open to suggestions. I also attached some pictures of the tooth in question.

 

Thank you very much!

 

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Im sure there a few glues that could handle this but for myself I would simply use a thick viscosity super glue for the big chuncks and some thin viscosity super glue for the smaller cracks.  Good luck

 

RB

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Harry Pristis

Consolidate the three pieces first, then glue them together.  Fill in gaps with epoxy putty.

Here is a workable technique for consolidating fossils.

Polyurethane will not give the desired penetration of the fossil. This resin is very difficult to remove. Putting polyurethane on a fossil is usually a bad idea.

I recommend against white glue (polyvinyl acetate) as a consolidant because there are better materials available.* (Normal prep lab dilution of white glue is one part water to two parts glue.) Rarely, a specimen cannot be dried without it crumbling, and white glue is the only reasonable answer. In my experience, white glue is messy and never looks good when the specimen is fully-prepared.

A much better material for bone is a polyvinyl butyral plastic such as Butvar B-76, but that material may be hard to find in small quantities. I have used this plastic, dissolved in acetone, for many types of fossils. (I have used it successfully on Silurian-age shales with brachiopods, for example.) It penetrates well, and in the proper dilution it produces a "damp-looking" finish with no gloss.

Butvar B-76 (but not other Butvar varieties) is also soluble in alcohol. (I assume that is denatured alcohol that you can buy in gallon cans.) I have never tried this solution for consolidation. The alcohol takes considerably longer to boil off the treated specimen.

Butvar B-76 and other suitable plastics, such as Vinac, are more frequently available on the Internet these days. But, if you can't find Butvar-76 or Vinac, you may want to fall back on a solution of Duco Cement (clear, like model airplane glue) in acetone. Duco Cement is not a first choice, or even a second; but, it will hold a fossil together while you consider other options.

Dilution? Start with a tube of glue dissolved in about five or six ounces of acetone in a glass jar with a metal screw-top. Shake well.

(From this point, the techniques are the same for any plastic consolidant you choose.) Adjust the dilution with more acetone until, after shaking, the tiniest air bubbles are just slightly retarded in their rise to the surface.

I usually heat specimens with an infra-red lamp to drive off moisture just before dipping the fossil. I do this with all sorts of fossils, and have never had one damaged by the heating. The untreated specimen is always at least as wet at the relative humidity of the air around it, I surmise. (A microwave oven may be as effective, but I've only dried glass beads for my air-abrasive unit.) Residual moisture may cause a white film to develop on the surface of a fossil after dipping in the consolidant.

Here's how the white film forms: As the acetone in the consolidant evaporates, the temperature at the surface of the specimen chills abruptly, lowering the dew-point at which ambient water vapor condenses.

 

And, that's my theory -- that the white film has two potential sources: residual interstitial moisture and ambient humidity condensing at the surface chilled by evaporation.

   Think about a plastic bag of food placed into a freezer, where frost is moisture and bag is the film of consolidant. Frost can form on either or both sizes of the plastic bag, inside frost from moisture in the food and outside frost from atmospheric moisture.

   My solution is heating the specimen to drive off residual moisture, and consolidating while it is warm to increase the dew-point at the specimen's surface, inhibiting condensation as the acetone boils off.

Do NOT heat the acetone solution directly. The acetone solution will get warm after dipping a number of heated fossils. You must have good ventilation to deal with the fumes!

I use a long-jawed forceps -- ten-inch tweezers, really -- to dip and/or retreive the fossils from the jar.

Ideally, you would submerge the dry specimen in this consolidant for a brief time (say 10-30 seconds, or until the specimen stops fizzing). Set each wet specimen aside to dry on cardboard (I use a beer-flat because that cardboard is absorbant and doesn't readily stick to the fossil).

To avoid pooling of consolidant which may drain from a bone, I rotate the bone once or twice in the first minute or two after placing it on the cardboard. This helps avoid a "drip-bead" of consolidant near the lowest point of the bone.

For a specimen too thick to be submerged, you can use a turkey-baster to flood the difficult areas. I treated an adult mammoth tibia that, because of its size, I dried in the Florida sun, then used the baster to pump consolidant into every opening of the bone.

I use a RubberMaid-type container to hold the consolidant for this basting step - that plastic seems to be impervious to the acetone. Get 'em at your local dollar-store.

Acetone evaporates very quickly. Replenish the consolidant mixture with a bit of acetone if you are using it on many specimens. Store it in a tightly sealed glass jar. Even if some acetone evaporates away between uses (it always does, it seems), you can reconstitute the solution by replacing the acetone.

Acetone is a nasty solvent. The fumes are explosive. The fumes are toxic. The liquid penetrates the skin-blood barrier. It's best to use gloves. Use in a well-ventilated area.
--------------Harry Pristis

* Here's what 'oilshale' had to say about white glue (wood glue is just another polymer formulation):

"Don't get me wrong - Elmer's White glue is a great stuff for glueing wood and can be also great for "hardening" crumbly fossils!

"But I fully agree with Harry's opinion (even so I am a polymer chemist and my job is to develop white glues and other latices....): I would never use a white glue unless the fossil is wet, crumbly and the substrate is porous and can't be dried before consilidation!

"There is no way to remove this white glue once dried (not even with solvent). It will form a dense polymer layer on the surface without penetrating much into the substrate (white glue are tiny polymer particles dispersed in water with a particle size of around 1µm, so the penetration depth won't be much).

"Butvar, a Polyvinyl butyrate (the company I am working in is also producing these polymers, of course different brand names) in this respect is much better (will penetrate better and can easily be removed by solvents).

"I do have a couple of fossil fish which were mistreated by someone else in such a way. Since the substrate was almost nonporous (diatomaceous earth!) and quite soft (and may be also the amount of white glue and concentration used was too high) there is now a thick slightly yellowish polymer film on top. Unfortunately, this is not all: The film shrinks and now peels off (with bones attached to the polymer film of course)!
Thomas"

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Thank you all very much for your answers and Harry Pristis, thank you for taking the time to write such an in depth explanation! I understand the reasons for avoiding PVA glue and will inquire as to where i can get some Butvar B-76. Sadly, i live in an apartment with my wife and my 3 cats, so ventilation is not exactly a strong point. :( If i just glue the pieces together with epoxy/super glue without consolidating, will the mammoth tooth keep breaking apart, or will it stabilize by itself, eventually? The rate of decay is pretty low, honestly, only very few small outer layer pieces sometimes fall apart, but very rarely...

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Harry Pristis
1 hour ago, Frog Dude said:

Thank you all very much for your answers and Harry Pristis, thank you for taking the time to write such an in depth explanation! I understand the reasons for avoiding PVA glue and will inquire as to where i can get some Butvar B-76. Sadly, i live in an apartment with my wife and my 3 cats, so ventilation is not exactly a strong point. :( If i just glue the pieces together with epoxy/super glue without consolidating, will the mammoth tooth keep breaking apart, or will it stabilize by itself, eventually? The rate of decay is pretty low, honestly, only very few small outer layer pieces sometimes fall apart, but very rarely...

 

The mammoth tooth will not stabilize by itself.  Eventually, the tooth will split again along the plane of cementum.  Mammoth teeth are notorious for this destruction.  If you have a table fan and an open window, you can control the acetone fumes.  Acetone is quite volatile and will not linger, if you use the fan.  You don't have a garden, a balcony, a patio?

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Paraloid B72 is soluble in ethanol and more readily available than PVA (Vinac).

 

Ethanol will take longer to “dry” than acetone but the fumes aren’t as offensive.

 

 

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Hey guys,

 

Sorry for the late reply, I've been away with my work. :(

 

@Harry Pristis - I have a balcony, but it is enclosed with windows, and no, no garden or patio. However, i do have a house in the countryside which is closed for the winter but I could go there when spring comes and try the procedure in the garden. I did find some Butvar here https://www.talasonline.com/Butvar-Resin?quantity=1&weight=7&Form=24 and plan on ordering some from the US. 1 pound should be enough? Also, what's the best way to keep the molar safe until i can stabilize it? I keep every piece wrapped up tightly in bubble wrap and all the pieces inside a closed bag...

 

@Ptychodus04 - Thank you for your suggestion. So i can pretty much follow Harry's suggestion but replace the Butvar 76 with Paraloid B72 and the acetone with ethanol?

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That is correct. You can directly substitute the two. All other processes should be the same. 
 

The dissolving of the Paraloid can take a long time. There’s a technique many use where you wrap the Paraloid in cheesecloth and suspend in your solvent to speed the process. I tend to be less technical about it when making smallish batches. I make mine in small pickle or olive jars. Measure out the required solvent and Paraloid. Add solvent to the jar and then pour the Paraloid pellets into the solvent. Close the lid tightly and shake it up.

 

It takes a long time for the Paraloid to fully dissolve so shaking every couple hours helps. It may take a few days for the plastic to fully dissolve in the ethanol. I have never used it as the solvent so I m not entirely knowledgeable there. It takes several hours using acetone.

 

1 pound will last you your entire life. I prep fossils daily and it takes me around 2 years to use a full pound of plastic. 
 

On another note, Paraloid makes a wonderful, slightly flexible, non degrading glue for repairing old books. I’ve even mixed it up in a thick consistency and used it as a binding agent to make a few paperback books.

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Thank you very much, Ptychodus04! I actually managed to find some Paraloid B72 nearby. Will order the substances and make the logistical preparations for the consolidating the molar. Thank you all very much for your help!

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