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What's covering my plesiosaur vertebra? How to clean


pachy-pleuro-whatnot-odon

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pachy-pleuro-whatnot-odon
20 hours ago, Ptychodus04 said:

Anything that is a rust remover should work. I would go with the ready made solution over the tablets.

 

Hmm, I think I'd prefer sticking to a tried and tested product, as with brand name specific product composition may also change, which may lead to uncertain results - particularly when talking about the long-term effects of it. Also, if going for a ready-made solution, how would you know if it's properly diluted and not to strong? How would you determine exposure time?

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Ptychodus04
19 minutes ago, pachy-pleuro-whatnot-odon said:

 

Hmm, I think I'd prefer sticking to a tried and tested product, as with brand name specific product composition may also change, which may lead to uncertain results - particularly when talking about the long-term effects of it. Also, if going for a ready-made solution, how would you know if it's properly diluted and not to strong? How would you determine exposure time?


Exposure time and strength are subjective. It’s not a precise formula. All you are doing is cleaning the pyrite. You can simply soak it in the Paraloid bath without treating with the rust remover and it will encapsulate the pyrite, preventing any further decay be eliminating moisture access. The cleaning process make them look nicer.

 

I’ve used CLR as well in the past.

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pachy-pleuro-whatnot-odon

Hi Paul,
 

On 3/4/2021 at 4:31 PM, paulgdls said:

Thank you for all your observations. Very interesting. I'd love to see some of the preserved organic tissue which is normally blasted away on those H. specimens.

 

Unfortunately, I haven't seen or spoken to these preparators for over a year now. But I plan to go by their workshop somewhere in spring, if our daughter allows, to see if they can help me with a tricky prep I'm stuck on. If, when there, I happen to see more of this organic residue, I'll take some pictures :)

 

On 3/4/2021 at 4:31 PM, paulgdls said:

The fossils have been cleaned of residual matrix using a dremel engraver with special tungsten tip (done under magnification, where necessary). Then scrubbed (with nylon toothbrush) with newly diluted glacial acetic acid using very hot water. This only for a minute or so. Then scrub under warm running water until the toothbrush does not show any colour due to matrix being removed. The acid / scrubbing procedure is what I would do on your plesiosaur vertebra to remove any oxidation products and loose material. I then use weakish paraloid painted on with a paint brush.

 

I was wondering about a couple of the peculiars of this procedure, such as how much you dilute the acetic acid and, consequently, how dangerous this procedure is (I don't really have too much experience yet working with acids, other than regular household cleaning vinegar and bleach, both in diluted form): I guess gloves and safety glasses are required, but is more precaution needed? Also, why dilute specifically with hot water? And is rinsing with running and, again, warm water necessary, or would a cold water bath work? I'm asking as the water in our area is, unfortunately, chlorinated, and thus would introduce its own acid... Lastly, don't all commonly available/normal toothbrushes have nylon bristles?

 

On 3/4/2021 at 4:31 PM, paulgdls said:

Love the proximal plesiosaur humerus from Sandsend. That deposit on it is certainly stable.

 

Thanks! It's indeed excellently preserved. I also particularly like the cross-cut at the bottom, as it excellently shows plesiosaur long-bone histology. Normally, the cancellous bone is also not as easy to make out, but in this particular specimen it is. I was very happy to acquire it.

 

On 3/4/2021 at 4:31 PM, paulgdls said:

Yes, I agree the plesiosaur vertebra does look big for a Cryptoclidus  and possibly for Muraenosaurus also. It might be from Peloneustes or another pliosaur. The foramina look too big for Muraenosaurus too.

 

Interesting! I hadn't really considered the size of the foramina. But the idea that this may, in fact, be a pliosaurian vertebra had crossed my mind. Something about the way the centra look, which reminds me of the later Kimmeridgian Pliosaurus macromerus specimens I've seen... I'm not sure whether the vertebra can still be identified, seeing as the one side of the vertebral centrum is damaged and the other is missing, but I'll see if I can have a look into it over the next few days. It may help me decide about what to do with the vertebra. Thanks for the tip!

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On 3/4/2021 at 2:27 PM, pachy-pleuro-whatnot-odon said:

I've grown to associate these kind of stains with pyrite-bloom, i.e. active and on-going pyrite decay. Also, since I've never experienced the spread of pyrite-decay, I don't quite know how much of a risk this actually is...

I've seen many examples of pyrite-bloom on Oxford Clay material and I can clearly see this In your example. Did the seller mention this when purchased, or had this developed over time. 

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pachy-pleuro-whatnot-odon
3 minutes ago, DE&i said:

I've seen many examples of pyrite-bloom on Oxford Clay material and I can clearly see this In your example. Did the seller mention this when purchased, or had this developed over time. 

Yes, that's exactly what's got me concerned. Neither photographs nor seller information at time of purchase mentioned the pyrite-bloom, but I discovered it shortly after having received the specimen. I've since spoken to the seller last week, who made no big deal of accepting the specimen back, almost as if expecting me to contact him about it. All I need to do now is make my mind up about whether or not to keep the piece. I'm still leaning more to returning it and getting my money back, as, in my opinion, the piece will always remain risky - no matter the seller claiming it has been stable for 30 years - but this potentially being a rare Callovian pliosaur vertebra has kind of got me bogged at the moment...

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paulgdls
12 hours ago, DE&i said:

I've seen many examples of pyrite-bloom on Oxford Clay material and I can clearly see this In your example. Did the seller mention this when purchased, or had this developed over time. 

 

@pachy-pleuro-whatnot-odon   @DE&i   Agreed this pyrite decay is a menace and often unstoppable. Just a thought, could the fossil be swapped (perhaps with a bit of uplift) for something more stable? Incidentally, the procedure I outlined above was for cleaning the fossils and does not get rid of unstable pyrite if its embedded (I've had to chuck away whole slabs of fossils due to pyrite decay, others I've managed to stabilise by grinding the pyrite off - a horrible process). For cleaning, pickling vinegar can be used in place of the diluted glacial acetic acid if there are concerns about safety. I decant the glacial using a large syringe, with attached tubing. Its not that corrosive if washed off quickly in large amounts of water. 

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pachy-pleuro-whatnot-odon

Hi Paul,

 

3 hours ago, paulgdls said:

Agreed this pyrite decay is a menace and often unstoppable. Just a thought, could the fossil be swapped (perhaps with a bit of uplift) for something more stable?

 

Unfortunately, I don't believe so. They only had the single vertebra of this morphotype. Moreover, the seller claims the fossil has been stable for thirty years, since it was dug up - a statement that you'd need to take at face value, but that I'm afraid might put the rest of my collection under unnecessary risk. It'll be a pity to send it back, though, as it was a beautiful specimen - and it's not as if I've seen too many Callovian vertebrae up for sale :s_confused:

 

3 hours ago, paulgdls said:

Incidentally, the procedure I outlined above was for cleaning the fossils and does not get rid of unstable pyrite if its embedded (I've had to chuck away whole slabs of fossils due to pyrite decay, others I've managed to stabilise by grinding the pyrite off - a horrible process).

 

This, for me, is exactly the reason I want to send the fossil back. The signs of pyrite-decay as just too clear to ignore. Yet it is uncertain to how much of the fossil's internal structure is affected. I'd rather not find out, though, as in the best-case scenario it'd cost me the purchase price of the fossil, but in the worst-case it would affect other parts of my collection. And while I may be able to remove outward traces of the pyrite-decay (although I care about appearance way less than stability), it wouldn't do too much to change the inherent constitution of the piece...

 

Notwithstanding it's good to know how and to what end these methods of cleaning can be applied, what to expect of them ;)

 

3 hours ago, paulgdls said:

For cleaning, pickling vinegar can be used in place of the diluted glacial acetic acid if there are concerns about safety. I decant the glacial using a large syringe, with attached tubing. Its not that corrosive if washed off quickly in large amounts of water.

 

Thanks, that's good to know! In fact, someone else suggested I use hydrochloric acid to finalize some tricky Triassic preps I've been working on. Hydrochloric acid for household use is quite easy to obtain in supermarkets here. But as I've only had limited experience with chemical preps, I'm always a bit concerned about "just giving it a try". May be that's the bad experience I had as a teenager when, after having helped out with a chemistry demonstration at school, I spoilt some acid on myself while cleaning up. Nothing too bad, but it did give me a bit of a fright. In any case, I still need to give that a try, and I though of using the same simple plastic pippets my wife uses for her essential oils for that...

 

As to the syringe: you mean something like the below? Just a regular plastic syringe and plastic tubing?

 

51W73aqSBuL._SL1000_.thumb.jpg.d78623e34745abd645cd31109260b814.jpg

 

Thanks again for all the help and advise! :D

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