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Preserving Lignite Fossils With Polyethylene Glycol


LoneRanger

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Lignite fossils are typically found in wet clays and sands. These fossils aren't very popular because, after being removed from the clay, they dry up and disintegrate as the moisture comes out of them.

I've been collecting some interesting lignite pieces in North Carolina, but couldn't find good info about preserving them on the forum or other websites. I tried coating lignite with polyvinyl acetate (PVA, aka Elmer's glue and other PVA-based wood glues) and it doesn't work well. PVA doesn't block moisture; you can clean it up with water, or add water to it to make it more workable. So, moisture slowly leaks out of the inside of lignite through the PVA coating, and the fossil shrinks and cracks. I've had to put on multiple coatings, to the point where you can see the whitish PVA over the lignite. I've had better luck spraying shellac on lignite, as it's waterproof. But the downside is that it leaves a surface gloss.

Finally, a professional paleontologist recommended polyethylene glycol (PEG). She had access to PEG through her university, but that wasn't an option for me. On the internet, I found that the Rockler Woodworking website sold PEG in 10-pound buckets. I ordered a couple of buckets, and got instructions for working with green wood. But I found that these instructions also work for lignite.

PEG is a solid that's like waxy ice. You need a hammer and chisel to break pieces out of the container, and you mix these with water. I make the solution in a 5-gallon bucket from a hardware or paint store. The water needs to be hot -- as hot as possible out of the hot water tap, because PEG dissolves more quickly in hot water. It still takes 12 to 24 hours to fully dissolve. The instructions are for making 30% or 50% solutions, and I've cut the difference in half and make a 40% solution. Basically, the more concentrated the solution, the shorter the time the piece needs to be immersed.

I put the lignite fossils in a plastic tub and pour PEG solution into the tub -- just enough to cover the fossils. I then cover the tub with clear plastic to prevent evaporation. Slowly, the PEG replaces the water inside the lignite. The instructions give a rough idea of how long a piece needs to be submerged for replacement to happen. The bigger/thicker the piece, the longer it takes.

Here is a photo of a couple of compressed Cretaceous pine cones that were in PEG for 18 days. Small and thin pieces like this are finished pretty quickly. They're still fragile after PEG treatment, but they're stable and don't disintegrate.

post-3634-0-71804100-1299539450_thumb.jpg

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did the PEG darken them?

"Your serpent of Egypt is bred now of your mud by the operation of your sun; so is your crocodile." Lepidus

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That was interesting. I wonder if it would work on wet paper shale (which get crumbly when dry)

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Good info; thank you very much!

"There has been an alarming increase in the number of things I know nothing about." - Ashleigh Ellwood Brilliant

“Try to learn something about everything and everything about something.” - Thomas Henry Huxley

>Paleontology is an evolving science.

>May your wonders never cease!

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Those are magnificent coalified cones. I don't recall seeing North Carolina fossil flora before.

Can you tell us about the formation and any other associated fauna or flora from that locality?

Thanks again for posting your spectacular cones !! :)

image.png.a84de26dad44fb03836a743755df237c.png

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i have been aware of PEG for some time but have never used it. here is a link regarding stabilizing wooden archaeological artifacts.

the way in which you described your experience with PVA puzzled me a bit. the issue with waterlogged/unstable wood is the shrinkage and structural collapse. inasmuch as the things you're trying to stabilize are fairly small, i'm wondering if an aqueous emulsion of PVA that's relatively thin wouldn't penetrate over time if a specimen were immersed in it and left covered to soak in it for a few days, and then slowly dried. the only reason i'm mentioning it is that you indicated the specimens remain fragile subsequent to the PEG treatment.

don't know. anyway, if you've found something that works for you, then that's a good thing.

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Thank you, 'Lone Ranger', for sharing your experience with PEG. The museum functionaries in Florida use PEG to preserve dugout canoes when these come to light.

I have never worked with PEG, though I should have on one or two occasions. Here's more info on PEG:

http://pristis.wix.com/the-demijohn-page

 

What seest thou else

In the dark backward and abysm of time?

---Shakespeare, The Tempest

 

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Interesting, I have some petrified wood I picked up last summer from a NC river, in addtition to the petrified pieces there are some lignite logs, branches,and bark, I imagine they're from the Cretaceous but they were found as float so I can't say for sure.

I've had them sitting in a large tub of water since last summer, not quite sure what I was going to do with them. Yesterday, I had pretty much made up my mind to give them the Elmer's Glue treatment since it's cheap and these things are large: 2 ft x 6" x4"; and probably not worth (to me) the cost to treat them with a better preservative. Sounds like you would advise against the Elmer's?

How much is PEG, enough to make 4 gallons or so?

I guess for the moment, I'll add some more water to the tub, keep thinking about it, and try not to look at that corner of the garage.

"There is no difference between Zen and Purgatory and Time Warner Cable, and they are trying to tach me this, but I am a dim impatient pupil."

----- xonenine

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Good to hear that the info is helpful. To answer a couple of the questions that came up:

- The PEG doesn't darken the lignite; the dark color in the photo is the natural color.

- Maybe saying that the PEG treated pieces are fragile is a little misleading. It's just that PEG doesn't harden or strengthen lignite. The pine cones are thin and easily broken right when taken out of the clay matrix, and PEG treatment doesn't do anything to strengthn them.

- I've never tried the method of immersing in PVA for days and then slowly drying out; maybe that would work better than just covering the piece in PVA using a paint brush (which is what I've tried). With the "paint brush" method, I have to reapply PVA again and again to stabilize the lignite.

- A 10-pound bucket of PEG costs $45, and a 40% solution makes almost exactly 4 gallons. The instructions don't cover a 40% solution, so I just split the difference between 30% and 50%.

- Sooner or later I'll put up a post about other plant and insect fossils from this site.

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Interesting thread... thank you for the information...... just a thought what would happen if one were to clean lignite fossils encrusted with clay and place them in a ultrasonic cleaner unit with 40% PEG... one would then pulsed the ultrasonic cleaner every 5 to 10 sec intervals ... the clay would go into suspension leaving the lignite fossils hopefully intact and pickled in 40% PEG.....

PL

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I've had pretty good luck with some carbonized cones/wood. I immersed them in acetone for a week to drive out all the water. Then immersed them in very dilute Vinac for 2 weeks. After removing from the Vinac and letting them dry, they have been pretty durable.

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PEG is also called Carbowax. You can order a free sample from Dow Chemicals. (I have web site bookmarked at work, but not here at home). I wrote a paper on its use to make temporary supports to work on delicate fossils published as part of the Tate Museum's 15th Annual Conference Guidebook. Available to you from me (at work) for a mere 15 bucks. (plus shipping). There are a bunch of other prep papers in there, but if anyone wants a pdf copy of my paper on carbowax, let me know. But hte fifteen bucks goes to the Tate Museum and will help us collect this darn T rex this summer.

Enough of the shameless plug. I love the stuff and use it a lot for microprep work.

You can also melt the carbowax on a hot plate then add it to your hot water... instant dissolvation! Keep in mind that carbowax is water soluble, so LoneRanger, keep those cool pine cones away from water.

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You can also melt the carbowax on a hot plate then add it to your hot water... instant dissolvation! Keep in mind that carbowax is water soluble, so LoneRanger, keep those cool pine cones away from water.

Thanks for that reminder jpc, I was thinking about keeping my lignite logs outdoors as yard art. Guess I'll have to go with PVA or something.

Or, maybe I should just take them back to the river and release them this summer!

"There is no difference between Zen and Purgatory and Time Warner Cable, and they are trying to tach me this, but I am a dim impatient pupil."

----- xonenine

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Great thread.. I've also had luck with a long soak of the PVA (Elmers 50/50) mix for some lignite. long soak, dry,-- long soak, dry, --long soak, dry.

Would like to try the PEG and see.

It's hard to remember why you drained the swamp when your surrounded by alligators.

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One last thought -- there's no harm in leaving the lignite piece in PEG for a longer time period than what may be necessary. The pro paleontologist told me that she put pieces in PEG for 6 months (just to be sure that they're fully stable), so you can just go with an extra long time period for soaking.

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