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Lyme Regis plesiosaur propodial with pyrite disease - how to treat


pachy-pleuro-whatnot-odon

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Hi all,

A couple of years ago I acquired a lovely pair of plesiosaur propodial bones from Lyme Regis. It was a matched pair of both humerus and femur. Today, when I was looking to make space in my cabinet for a new acquisition I had made, I discovered some odd dust next to the humerus that, on inspection and to my horror turned out to be pyrite bloom! I immediately removed the specimen from the cabinet, checked the other podial and nearby fossils, and used a tooth brush to brush of the most direct traces of pyrite decay. But the question is: what now? How do I ensure the propodial's preservation, and make it safe for display again. Should I store affected piece in an open or closed container? I suspect the latter, together with silica beads to consume any excess moisture might be best right now. But how do I get to the point where I can take it out again? Any suggestions are welcome.

 

From my own thread on this topic I know of the existence of pyrite stopper, which sounds ideal for this situation. But I've also been warned that this is quite a hazardous solution and am therefore afraid of trying this out myself. So, part of the question would be whether someone offers pyrite treatment as a service, of knows of someone who does.

 

Thanks in advance for your help!

 

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@Ptychodus04 @DanJeavs @paulgdls @RuMert and others

 

 

Edited by pachy-pleuro-whatnot-odon
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'There's nothing like millions of years of really frustrating trial and error to give a species moral fibre and, in some cases, backbone' -- Terry Pratchett

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try to clean it out as much as possible and then seal it with paraloid B72 . I can't guarantee it will work, but that's what I would do.

 

once the decay has started there is not much els you can do I think.

Edited by Manticocerasman
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growing old is mandatory but growing up is optional.

 

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Apart from the pyrite stopper, I've also heard of people just blasting or prepping the decay product of and then indeed sealing it, to prevent further decay. Since I bought this piece from a befriended seller three years ago, and this UK-based seller also provides preparation services, I decided to also get in touch with them to see if they might offer services to help stabalize the decay. I'm still awaiting a response. But with the Oxford Show taking place this weekend, it may be a while before I get an answer. There a couple of other UK-based preparators that I might give a try in case the original seller can't help me. But as I can't blast the spot myself (I lack the equipment) and don't want to dig a hole in the bone, getting someone from the UK with experience in Lyme Regis material involved doesn't seem like a bad idea at this point... Especially since the propodials are a matching pair, it would be a real shame to loose one of them. Moreover, the morphology of the specimen is relatively unique to the early stages of the Jurassic, so it's the only specimen I've got and not easy to replace...

'There's nothing like millions of years of really frustrating trial and error to give a species moral fibre and, in some cases, backbone' -- Terry Pratchett

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Pyrite decay is a slow process. It won’t hurt the specimen to sit for a few weeks until prep can be done as long as you isolate it from the other fossils. The sulphuric acid produced by the decay is pretty indiscriminate.

 

 

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43 minutes ago, Ptychodus04 said:

Pyrite decay is a slow process. It won’t hurt the specimen to sit for a few weeks until prep can be done as long as you isolate it from the other fossils. The sulphuric acid produced by the decay is pretty indiscriminate.

 

Thanks, Kris! Good to know, as I do hope to find someone who can help me with this and that may take some time, especially if I need to have the specimen shipped... I've already isolated the specimen (though haven't added silica gel yet, as I don't seem to have any packs lying around! :o Hopefully I can pick up some nearby or order some online. I've also cleaned the spot with a moistened kitchen towel. Hopefully that'll be enough to clean up any traces of the sulphuric acid and make the shelf save for storing other fossils on again (the shelf is laminated)...

 

Other than that, any recommendations on how to deal with or treat this kind of affliction? I mean, I might not need to act immediately, but I will need to act eventually...

Edited by pachy-pleuro-whatnot-odon
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'There's nothing like millions of years of really frustrating trial and error to give a species moral fibre and, in some cases, backbone' -- Terry Pratchett

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A little pyrite dust is not a verdict:D Lots of specimens are for years exposed to different weather conditions and get afterwards covered by grayish dust but nothing happens to them. I have many pyritized specimens but didn't lost anything apart from 2-3 vertebrae sets which were already in poor condition

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13 minutes ago, RuMert said:

A little pyrite dust is not a verdict:D Lots of specimens are for years exposed to different weather conditions and get afterwards covered by grayish dust but nothing happens to them. I have many pyritized specimens but didn't lost anything apart from 2-3 vertebrae sets which were already in poor condition

 

While true and something a lot of museums with collections from pyrite-rich deposits work based upon, such external symptoms of decay belie the decay going on inside such pieces. Agreeably, the decay may go very slow, but it's likely to still take place and pose a risk to other specimens. That's why museums continuously remove and treat such visible traces of pyrite disease...

'There's nothing like millions of years of really frustrating trial and error to give a species moral fibre and, in some cases, backbone' -- Terry Pratchett

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1 minute ago, RuMert said:

For example, a pyritized ammo I found a year ago. It was exposed to everything and already covered with gray dust. Guess what? Nothing happened to it

IMG20201011132621.jpg

 

I guess, though, there might be a difference between a specimen that had already reached a stable state of decay, versus one that has just started showing signs of it, after having been stable for three years or more...

'There's nothing like millions of years of really frustrating trial and error to give a species moral fibre and, in some cases, backbone' -- Terry Pratchett

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Neutralization of the sulphuric acid and low relative humidity are the most important factors. Coating / Sealing with Polyvinyl acetate, Shellac or Polybutyl Methacrylate (Paraloid) is not effective and not recommended anymore.Pyrite Oxidation Review and Prevention Practices.pdf

Edited by oilshale
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Be not ashamed of mistakes and thus make them crimes (Confucius, 551 BC - 479 BC).

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6 minutes ago, oilshale said:

Neutralization of the sulphuric acid and low relative humidity are the most important factors. Coating / Sealing with Polyvinyl acetate, Shellac or Polybutyl Methacrylate (Paraloid) is not effective and not recommended anymore.Pyrite Oxidation Review and Prevention Practices.pdf

 

That's what I've heard as well... As I understand it, there's no guarantee of an airtight seal, you might lock in humidity and/or sulfuric acid and either continue or exacerbate the decay, and complicate further future treatment.

 

12 minutes ago, RuMert said:

With valuable specimens I'd 1st heated them on a stove (kills bacteria), then covered with Paraloid or varnish. A popular method here is boiling in paraffin, I've never practiced it

 

I recently got a batch of fossils that had been treated with paraffin fifteen years ago. I can't say I was overwhelmed by the results. The fossils were dark with little detail visible, and felt brittle to the touch. Obviously the paraffin was holding the specimens together as a surface coating, but hadn't had any penetration. So I removed the paraffin (as best I could), heated the specimens up, and dunked them in Paraloid. The result is that a lot more detail is visible now, and the fossils no longer feel as brittle...

 

Your suggestion of heating the specimen in an oven might be worth a try, though :b_idea:

'There's nothing like millions of years of really frustrating trial and error to give a species moral fibre and, in some cases, backbone' -- Terry Pratchett

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21 hours ago, Manticocerasman said:

try to clean it out as much as possible and then seal it with paraloid B72 . I can't guarantee it will work, but that's what I would do.

 

once the decay has started there is not much els you can do I think.

 

I agree. Clean it by grinding the bloom off to a smooth surface (this gives minimum surface area), wipe with a rag soaked in acetone to remove the dust, then apply a couple of layers of thick paraloid. This has worked on a number of my fossils where the pyrite decay isn't too bad. Often the surface layers are the worst affected and once they are removed (which can take repeated removal over a number of years) the fossil is stable. 

 

all the best

 

Paul

 

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49 minutes ago, paulgdls said:

 

I agree. Clean it by grinding the bloom off to a smooth surface (this gives minimum surface area), wipe with a rag soaked in acetone to remove the dust, then apply a couple of layers of thick paraloid. This has worked on a number of my fossils where the pyrite decay isn't too bad. Often the surface layers are the worst affected and once they are removed (which can take repeated removal over a number of years) the fossil is stable. 

 

all the best

 

Paul

 

Thanks, Paul! Will give this a try!

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'There's nothing like millions of years of really frustrating trial and error to give a species moral fibre and, in some cases, backbone' -- Terry Pratchett

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Just read that Paraloid B-67 might be better as a sealant after removal of the bloom, for its hydrophobic properties, but that it does tend to turn yellow with exposure to sunlight/UV. Anybody have any experience with this product? @Harry Pristis may be?

'There's nothing like millions of years of really frustrating trial and error to give a species moral fibre and, in some cases, backbone' -- Terry Pratchett

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Okay, so at least I've now got my packs of silica gel, which, together with the closed container and having brushed away most of the surface bloom should buy me some time, at least, while I figure out what exactly to do... Using a pyrite stopper may still be on the table after having received a link to this blog-post. Haven't read it yet, but it looks both informative and hope-giving.

'There's nothing like millions of years of really frustrating trial and error to give a species moral fibre and, in some cases, backbone' -- Terry Pratchett

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  • 3 weeks later...

The following article may be informative on the practical application of ethanolamine thioglycollate (a.k.a. pyrite stopper), following procedures used at the British Museum of Natural History. It also illustrates how far back application of the treatment goes, and demonstrates its professional support. However, from discussions with Kate Acheson-Dumbravă and Paul Davis (who has dealt with pyrite cases at the BMNH) it has since become clear that 1) pyrite occurs in two crystalline forms - stable and unstable - and that 2) while ethanolamine thioglycollate is able to stabilise unstable pyrite crystals, 3) a specimen, more often than not, contains only one form of crystallization but not the both, thus 4) requiring continuous monitoring following treatment, as well as repeat treatments. In other words, even with pyrite stopper, pyrite decay seems unstoppable, and can only be slowed down.

 

From discussions with Kate and Paul it has furthermore become apparent that cleaning/grinding off the decayed surface will only slow down the decay process (but not temporarily halt it, as with ethanolamine thioglycollate) for the same reasons as above, being that the crystalline structure of the pyrite is of uniform type throughout a specimen, and therefore causing it to be equally susceptible to decay. In contrast to using pyrite stopper, however, the decay products are not stabilised and removed, nor is the sulphuric acid, meaning that, unbeknownst to the outside observer, pyrite decay may continue inside the specimen to the point of the latter, at one point, simply crumbling to dust when it becomes just an outer shell.

 

All of this hasn't really helped me figure out how to treat my current specimen yet, but they're steps on the path getting there... The enclosed article, for example, mentions that

 

Quote

[d]espite [...] [the] fairly low toxicity [of ethanolamine thioglycollate], precautions should be taken against the possible hazards associated with its use. Its corrosive action necessitates the wearing of PVC gloves and goggles for eye protection, and its use should be restricted to a well ventilated area (preferably a fume cupboard).

 

The aforementioned blog-post also warns about a bad smell, so it's probably best to attempt this in an outside and well-ventilated area (yet out of the sun, since we are dealing with alcohol, after all).

 

Ironically, I'm coming to the realisation that this is pretty much the same information Johnny already gave me way back. But having spoken to more people in the know, I now feel like I've got a better understanding of the treatment. To be continued...

780819112_Cornish1987PyriteTreatmentEthanolamineThioglycollate.pdf

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'There's nothing like millions of years of really frustrating trial and error to give a species moral fibre and, in some cases, backbone' -- Terry Pratchett

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Another interesting finding to come out of my conversation with Paul Davis is the understanding that, contrary to popular belief, pyrite decay is not transmissible: although it is true that the sulphuric acid given off by the decay of an unstable specimen will affect labels, trays and even wood cabinets, nearby specimens containing pyrite's stable crystalline form will not be affected. Specimens that are made up of the unstable crystalline form, like the decaying specimen itself, however, may start to decay more rapidly by exposure to the sulphuric acid.

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'There's nothing like millions of years of really frustrating trial and error to give a species moral fibre and, in some cases, backbone' -- Terry Pratchett

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  • 2 months later...

It's been a while, but I thought I'd follow this story up with its conclusion, so that others way learn from or, otherwise, look back on my experiences.

 

So I decided to send the humerus over to a preparator in the UK who's got extensive experience in professionally (museum-level) dealing with pyrite-affected pieces. While this definitely wasn't the cheapest option available to me (treatment ended up costing me more than the specimen had originally), this is primarily due to the cost of the 99.9% pure ethanol needed to wash the piece in between subsequent treatment cycles. However, I felt the expense was worth it due to the rarity of the bone. In addition, the treatment should also put me in the clear for hopefully a decade or so (if not more), which made the expense worth the investment.

 

After having received my specimen, the preparator first recorded it's current state and send me a few lines and photographs by way of report. Turns out that both ends of the humerus were affected by pyrite - something I had actually already discovered myself when packing the sample for shipment - leading to concern whether the decay could run all through the length of the piece, making my choice to have it professionally looked at all the better. There were also some old restorations that I was warned could come undone during treatment due to the prolonged exposure to alcohol. We agreed that if this would happen, he would apply new repairs. This report coincidentally proved a good moment for me to do some research into the provenance and conservation history of the specimen to try and figure out what materials had been used to conserve it previously, although in the end it didn't make much of a difference.

 

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Treatment with ethanolamine thioglycollate (C₄H₁₁NO₃S, commercially known as "pyrite stopper") takes time, as the specimen under treatment undergoes multiple cycles of immersion in a 3%-solution on the basis of isopronanol (Propan-2-ol, CH₃CHOHCH₃) and is rinsed in ethanol (CH₃CH₂OH) at the end of each cycle. Dry application is possible, but less effective, as treatment can only go as deep into a specimen as capillary processes will allow the solution to penetrate. In my case, therefore, full immersion was applied at 10 cycles of four hours, followed by 24 hour washes in ethanol.

 

Once this treatment was complete, one of the old repairs had indeed become undone, which, however, was fixed easily enough. The break, however, did allow inspection of the bone's internal structure, which, luckily, proved unaffected. Previous glues, varnishes and paints were removed from the surface; the surface lightly air abraded with Fe-powder; and the break repaired with epoxy resin and milliput epoxy putty. The specimen then received some new water based acrylic paints to touch it up, and the surface consolidated with Butvar B-76 dissolved in Methyl Ethyl Ketone (MEK, CH₃COCH₂CH₃ Butanone). Pictures below are before application of the Butvar-consolidant.

 

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The preparator then vacuum packed the humerus in vapour barrier film with oxygen scavengers and a silica gel moisture absorber (a more expensive option that mine is to go for Escal vapour barrier film and RP5 scavengers), which is how I received the specimen earlier this week together with a complete description of the treatment that had been applied. An Oxygen Indicator Eye has been stuck directly next to the specimen and will turn deep purple to blue when the oxygen scavengers need to be replaced, whereas the silica gel will change from orange to yellow/clear when that needs to be replaced. Of course the specimen can also be taken out of the barrier film (although it will then not be able to be repackaged without a vacuum-machine), but will last longest inside the film.

 

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All in all I'm quite satisfied with the result and feel confident that the specimen should last me for quite a number of years to come :)

 

(all photographs posted with permission)

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'There's nothing like millions of years of really frustrating trial and error to give a species moral fibre and, in some cases, backbone' -- Terry Pratchett

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