Is It Safe To Clean Suspected Crab And Lobster Material In Diluted Vinegar?

[claire01]

I know it isn't safe for some material so I thought I'd ask the experts before I proceed. I have tried googling this but the search usually takes me to tasty recipes which is not helpful in this case. I don't see it addressed specifically here either.

I'm using a dental pick until I come to even a tiny bit of resistance so as not to loose the fine detail, but this leaves a film of matrix that no amount of soap and water seems to remove. Any advice?

[mammothhunter]

I would give it a try, with a q-tip.

It depends on how much of the chitin has been replaced and if the matrix is something like limestone, which is calcium carbonate.

So, in theory, if the original chitin is still relatively present, it will be more resistant than the limestone to the acid, much more so, since chitin is a protein.

But I think trying a little bit on a q-tip shouldn't hurt much.

[JimB88]

knowing the type of matrix would help in determining the best prep methods. Vinegar for instance only works on limestone (and dolostone to a lesser extant.)

[claire01]

Thank you so much, you guys. Shale and limestone? They are from the Britton member of the Eagle Ford formation in Texas.

[CH4ShotCaller]

Indeed, the matrix surrounding the specimen has a lot to do with prep method(s). If the chitin is reasonably intact, I use a rotary dremmel with a small wire wheel (not brass) to help take some of that sticky material of the surface. But, that doesn't always apply for mine either. That last crab I prepped was 'powdery' and would not take a wheel or any other solvent. Sometimes, you'll have to just leave 'em as they are with some matrix attached... gives 'em a wee bit of character.

[FossilDAWG]

I think you should try it with a specimen you wouldn't care about if it ended badly. Every situation is a bit different, so the only people who will be able to give you solid advice are people who have experience with those Britton nodules/cobbles. Personally, all I have found that works is very slow patient scraping with a sharpened needle, under the microscope. However, I haven't tried any form of acid treatment on them. You could also take a piece of the matrix (without any fossil in it) and submerge it in the acid and see if it bubbles. If it does, the rock is at least partly carbonate and will dissolve, if it isn't the method won't work. I recall those hard nodules are ironstone, not carbonate, so the acid probably won't do anything, but I may be wrong. Nothing like an actual experiment to find out for sure.

One thing I would worry about, even if the crab/lobster shell is resistant to the acid, the acid will enter any crack or break in the shell and hollow out the matrix from the back (that is, if the acid works at all). The fossil will then be so fragile it will crumble at the slightest touch. The only way to avoid this is to inspect the fossil frequently during the etching process, and seal up any cracks with wax to keep the acid from entering. At the end of the process the wax can be removed with acetone. Needless to say this is a very slow tedious process.

Don

[claire01]

Thank you all so much for the great advice. I've always admired the skill and patience crab preppers possess and now having tried a tiny bit of it myself, my respect for y'all has reached a new level. I think I may just stick to trying to stumble onto the ones nature has prepped for me. I did buy an electric engraver a while back, but even it seems heavy handed when it comes to these little crabs I sometimes find. Thank you again, I sincerely appreciate your willingness to share your expertise.

[jpc]

One thing I would worry about, even if the crab/lobster shell is resistant to the acid, the acid will enter any crack or break in the shell and hollow out the matrix from the back (that is, if the acid works at all). The fossil will then be so fragile it will crumble at the slightest touch. The only way to avoid this is to inspect the fossil frequently during the etching process, and seal up any cracks with wax to keep the acid from entering. At the end of the process the wax can be removed with acetone. Needless to say this is a very slow tedious process.

Don

Don... you remove wax with acetone? I have never heard of this working. I would coat the fossil with Vinac or somesuch, and then at the end remove that with acetone, if needed. But yes, if the acid works on this, microscopic cracks in the crab will allow acid into the crab and weaken it from the inside unless it is protected.

[claire01]

I've put this idea on the back burner for now. The last thing I want to do is compromise the structural integrity of any of my fossils. I do remember reading somewhere, probably here, that a soak in baking soda after using vinegar neutralizes the acid. Will do a little more reading on the subject before doing anything rash. Thanks again, you guys

Edited May 16, 2014 by claire01