Preserving Mastodon Tusk

[AroHed]

I treated a section of mastodon tusk with shellac and denatured alcohol. It appears like I did not use enough of one/both. Can I re-treat it?

[jpc]

That is a tough call. Tusks are notoriously nasty, and shellac is also notoiously nasty. By the time you donate this ti your grandkuds the shellac (which never truly sets) will have turned yellow and attracted a ton of micrscopic dust, leaving a permanentlt dusty tusk.

[RJB]

Ive never worked on a mammoth tusk before, but many years ago a fellow told me to use Elmers on mammoth teeth. Not sure if it works or not.

RB

[jpevahouse]

Denatured alcohol is strong stuff. Don't think I'd use it on fossils. Fishermen who dredge fossils from the NJ continental shelf often use marine varnish. It seems to give a hard protective layer but is very glossy and I don't know how it will look 20 years from now.

I've been using a solution of Elmers glue and water. The advantages are it does give a protective coating and being water based can be removed later if there is age discoloration. I have stuff with Elmers glue from 20 - 25 years ago that still holds well and no noticable discoloration.

[Harry Pristis]

I am surprised anyone would recommend white glue after all the discussions we've had about it.

Denatured alcohol is not destructive to fossils . . . I don't know where that idea comes from. It's poisonous if you make a highball with it. It is the alternate solvent for Butvar B-76.

I don't have any experience with shellac on fossils . . . that is far out of mainstream preparation these days. This challenge may be hopeless already; but, here's what I might do: I'd go to this page to learn about using plastic consolidants http://www.thefossilforum.com/index.php?/user/42-harry-pristis/

Then, I might mix up a substantial batch of plastic in acetone. I might then soak the ivory for an hour or more (until after the surface shellac has disappeared into solution). I'd gently remove the ivory from the solution (or decant the consolidant solution). Allow the ivory to dry.

If the ivory has come apart in the process, let dry, then use the white glue to put it back together as best you can. You probably should not further use the consolidant which is (we hope) contaminated with shellac.

Let us know how you proceed and what results you achieve.

[jpevahouse]

Elmer's Glue becomes transparent when dried. I have used it for more years than I can remember with no adverse affects. It simply applies a clear hard water based coating to protect the fossil which can easily be removed at a later time. Other substances and techniques may not be so easy to remove later on if desired.

Denatured alcohol is a solvent commonly used for cleaning and refinishing. It can dissolve lots of stuff like varnish on old furniture.

Edited February 23, 2016 by jpevahouse

[Harry Pristis]

Elmer's Glue becomes transparent when dried. I have used it for more years than I can remember with no adverse affects. It simply applies a clear hard water based coating to protect the fossil which can easily be removed at a later time. Other substances and techniques may not be so easy to remove later on if desired.

Denatured alcohol is a solvent commonly used for cleaning and refinishing. It can dissolve lots of stuff like varnish on old furniture.

Well, one of us is wrong. 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 gluing 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" [emphasis added]

[amour 25]

Tusk is nasty if allowed to dry as will curl.

I have found pieces biggest one say 20 inches and 12 around at back, but I used a Butvar to glue it up, you can use it wet will leave a white film, water causes that , but can be made to do away after a full dry just re brush with acetone.

So good luck with it, I have used white glue on Bison skulls very diluted no problem so far, about 16 years back now.

Edited February 24, 2016 by amour 25

[paulgdls]

I've used dilute PVA on ice age fossils such as large tusks for 20 years with very good results. If the fossil is wet it is the best consolidant.

Paul

[Ptychodus04]

Elmer's Glue becomes transparent when dried. I have used it for more years than I can remember with no adverse affects. It simply applies a clear hard water based coating to protect the fossil which can easily be removed at a later time. Other substances and techniques may not be so easy to remove later on if desired.

Denatured alcohol is a solvent commonly used for cleaning and refinishing. It can dissolve lots of stuff like varnish on old furniture.

Easily removed is definitely a subjective phrase. It is easier to remove than some things used in the past, but it is not what I would consider easy. I just worked on a mammoth tooth that had been covered in white glue. It had started to yellow and a glue joint had completely failed. The owner wanted it repaired and the white (now yellow) glue removed. I had to soak the whole thing in acetone for 2 days and then spent the next few days picking slightly tacky glue boogers off it.

Unfortunately, I also had to deal with the thing falling apart. A bit of Paleobond took care of the breaks and the whole thing got a generous helping of PVA. Apoxie Sculpt filled the cracks and we now have a stable fossil.

If you need an emulsion to deal with wet fossils, you can make one with PVA or Butvar which is much more stable.

[Harry Pristis]

Thank you for the testimonial, Ptychodus04. It has been a long time since I undertook to remove white glue from a fossil; but, I remember the time-consuming mess.

White glue (a water emulsion of polyvinyl acetate) is inexpensive, readily available, and non-toxic to use. However, it is not the material to use to consolidate vertebrate fossils (with the possible exception of wet, crumbly bone or ivory which can't be dried before consolidation).

More expensive, less-easily available, and less easy to use materials are the choice of professional and advanced-amateur preparators. If a vertebrate fossil is to look good now and a hundred years from now, state of the art materials should be used for consolidation.