OctoDude Posted January 8, 2017 Share Posted January 8, 2017 Hello, Long time occasional lurker, first time poster; I hope this is the appropriate place and method for posing this question, and I apologize if it is not! I have some limestone blocks containing conodont teeth and shark teeth, which I would like to break down with acetic acid. From what I have read, adding a buffer to the acid solution would greatly help in preventing damage to the teeth (and especially the roots), but I have no idea what buffers are readily available (and from where they would be available) and commonly used (and how much is needed). Can anyone advise? Any experience you've had with buffering acetic acid for dissolving limestone matrix to retrieve small teeth that you'd be willing to share would be greatly appreciated! Much thanks! :-) Link to comment Share on other sites More sharing options...
JohnJ Posted January 8, 2017 Share Posted January 8, 2017 You might try to see if hydrogen peroxide has any effect before you try the acid. Varied matrix from formations will react differently to acid. Diluting with water could be a good way to start. I would begin with a slightly acidic solution first, then view the effects on the fossil material under the microscope to see if the soak time or acid concentration was too great. 2 The human mind has the ability to believe anything is true. - JJ Link to comment Share on other sites More sharing options...
OctoDude Posted January 8, 2017 Author Share Posted January 8, 2017 Thank you for your response, JohnJ! I have used hydrogen peroxide on a number of different matrices with varied results (from extremely successful to almost no change at all); this limestone matrix seems to be impervious to disaggregation by it. If I can't find an appropriate buffering agent, then greatly diluting the acid might be my only option. Thanks again! Link to comment Share on other sites More sharing options...
Ptychodus04 Posted January 8, 2017 Share Posted January 8, 2017 I regularly use white vinegar (5% acetic acid) to dissolve limestone blocks with shark teeth. No buffer and no damage to the teeth with soaks (replacing acid every couple days) lasting over a month. 3 Regards, Kris Global Paleo Services, LLC https://globalpaleoservices.com http://instagram.com/globalpaleoservices http://instagram.com/kris.howe Link to comment Share on other sites More sharing options...
OctoDude Posted January 8, 2017 Author Share Posted January 8, 2017 Thank you for your response Ptychodus04! Maybe I am just worried over nothing; I have been told multiple times that acetic (even in low concentrations like in vinegar) could eat teeth (especially the roots), so I wanted to be extra careful... Do you replace the acid when the solution stops bubbling, or just every couple of days as a matter of course? And do you rinse or soak the matrix in water between acid soaks, or just go straight from one soak to the next? When a tooth is partially exposed on a block, do you cover it with something to protect it from the acid, or not worry? Sorry for all the questions, and thank you again for your response! Link to comment Share on other sites More sharing options...
Doctor Mud Posted January 8, 2017 Share Posted January 8, 2017 Hi Octodude. I did a lot of reading and a few experiments a while back to work out the best protocol for teeth I was extracting from a calcerous matrix. See this post: I based my protocol on a couple of detailed papers by Jeppsson. Back then the upload limit was to low for me to upload the papers but I can do that now. I found that I was fine using off the shelf white vinegar for dissolution, but after a certain amount of the matrix was dissolved the acid started attacking the teeth. Jeppsson suggested using a buffered acetic acid solution of pH 4.5 (from memory, I'll need to check the papers). The acid was made up of leftover solution from dissolving the matrix during previous extractions. A solution dubbed "acetate soup" by Jeppsson. You basically take a block of your matrix and dissolve it until no dissolution takes place, then adjust to the required pH using fresh acetic acid. I tested a range of pH levels on common teeth from 3.5 to 4.5 and these were all fine. You may be ok just using white vinegar if the concentration of teeth is low - I.e the ratio of matrix to teeth is high. That way there would always be plenty of other carbonates to buffer the teeth against dissolution by the acid. That seemed to be the case with my samples. They were from a concentrated tooth/bone horizon so once a lot of the matrix was dissolved the acid started attacking the teeth. I would try some experiments first if you have spare matrix. Ill post the papers soon. 5 Link to comment Share on other sites More sharing options...
Doctor Mud Posted January 8, 2017 Share Posted January 8, 2017 Hi there - here are the Jeppsson papers on extracting tooth or tooth like elements using acid Jeppson et al 1985 Acetic acid and phosphatic fossils.pdf Abstract: Dilute acetic acid is shown to be highly destructive to conodont elements. A solution containing about 7% acetic acid and 2% calcium acetate is nondestructive. It can be produced by mixing 7% concentrated acetic acid, 63% water and 30% of the solution left after the dissolution of previous samples. A regular testing of the effect of the solution used is recommended. Samples previously considered to be barren should be rechecked. It is necessary that reports on frequencies of any kind of phosphatic fossils include information on which dissolution method was used. The adverse effect of ammonium chloride if left on calcium phosphate fossils is noted. Jeppsson et al 1999 Acetate buffered solution for extracting phosphatic fossils.pdf Abstract: When extracting or cleaning phosphatic fossils using acetic acid, the solutions must be buffered with calcium acetate to a pH greater than 3.6 for conodont and many fish taxa, and to a slightly greater pH for some conulariid, shark, and some fish taxa. Diagrams of the changes in pH and density during dissolution, rate of dissolution, and productivity per liter of acid provide a means for selecting the economically optimal process, monitoring the progress ,and adjusting the composition of the solution when necessary. The files actually aren't that large so maybe I did upload them elsewhere. I hope you find them useful! 5 Link to comment Share on other sites More sharing options...
OctoDude Posted January 8, 2017 Author Share Posted January 8, 2017 Outstanding, Doctor Mud, thank you very much for all of your help, and the papers! What kind of pH meter do you recommend? Link to comment Share on other sites More sharing options...
Doctor Mud Posted January 8, 2017 Share Posted January 8, 2017 You are welcome I can't remember which brand I used, but I would make sure it is one that can be calibrated. Mine is packed away since we are in the process of shifting. A good unit should come with a couple of calibration solutions so you can make sure you are getting accurate results an acidic and alkaline solution of known pH. Mine didn't cost the earth - I think I paid less than $100 AUD for it. Also make sure the unit corrects for temperature as pH also depends on this. I did the usual thing and checked online reviews for the brand before I committed. Good luck with the extraction. 1 Link to comment Share on other sites More sharing options...
OctoDude Posted January 8, 2017 Author Share Posted January 8, 2017 Thank you very much! :-) Link to comment Share on other sites More sharing options...
Coco Posted January 8, 2017 Share Posted January 8, 2017 Hi, 8 hours ago, JohnJ said: You might try to see if hydrogen peroxide has any effect before you try the acid. Varied matrix from formations will react differently to acid. Diluting with water could be a good way to start. I would begin with a slightly acidic solution first, then view the effects on the fossil material under the microscope to see if the soak time or acid concentration was too great. The hydrogen peroxide is available only on clayey sediments. To be effective, it is necessary to use it when the clay is very dry. If one dissolution isn't sufficient, it is necessary to rinse the sediment with a fine sieve, to let it dry completely and dip back it into the hydrogen peroxide (often diluted in 10 %). Coco 2 ---------------------- OUTIL POUR MESURER VOS FOSSILES : ici Ma bibliothèque PDF 1 (Poissons et sélaciens récents & fossiles) : ici Ma bibliothèque PDF 2 (Animaux vivants - sans poissons ni sélaciens) : ici Mâchoires sélaciennes récentes : ici Hétérodontiques et sélaciens : ici Oeufs sélaciens récents : ici Otolithes de poissons récents ! ici Un Greg... Link to comment Share on other sites More sharing options...
OctoDude Posted January 8, 2017 Author Share Posted January 8, 2017 Bonjour Coco, and thank you for your response! I have used the hydrogen peroxide technique you describe many times on matrices containing significant clay content, but these limestones are very hard, which is why I was looking for an acid technique to break them down. Thank you also for the library of .pdf files you have uploaded and shared, it has been useful to me several times! :-) 1 Link to comment Share on other sites More sharing options...
Coco Posted January 8, 2017 Share Posted January 8, 2017 It is always with a great pleasure ! Coco ---------------------- OUTIL POUR MESURER VOS FOSSILES : ici Ma bibliothèque PDF 1 (Poissons et sélaciens récents & fossiles) : ici Ma bibliothèque PDF 2 (Animaux vivants - sans poissons ni sélaciens) : ici Mâchoires sélaciennes récentes : ici Hétérodontiques et sélaciens : ici Oeufs sélaciens récents : ici Otolithes de poissons récents ! ici Un Greg... Link to comment Share on other sites More sharing options...
ArrestedBeauty Posted January 9, 2017 Share Posted January 9, 2017 I am so very new at this, I have extra training ground wheels...that being said, I have found a pumice stone from the grocery store (marketed for porcelain) is quite effective at removing the stubborn clay. I also use the5 Purple 3m/Scothb Brite scrubbers given their high mineral content, I have also found a Mr. Clean Magic Eraser to be effective on even heavily desicated clay, it will even remove the softer matrix. It also removes paint "rub off" after a miner "incident" or "inappropriate stroking" of something else. Mind the clear coat though...ithat does dull it, but definitely a better option in many cases. Link to comment Share on other sites More sharing options...
Ptychodus04 Posted January 9, 2017 Share Posted January 9, 2017 22 hours ago, OctoDude said: Thank you for your response Ptychodus04! Maybe I am just worried over nothing; I have been told multiple times that acetic (even in low concentrations like in vinegar) could eat teeth (especially the roots), so I wanted to be extra careful... Do you replace the acid when the solution stops bubbling, or just every couple of days as a matter of course? And do you rinse or soak the matrix in water between acid soaks, or just go straight from one soak to the next? When a tooth is partially exposed on a block, do you cover it with something to protect it from the acid, or not worry? Sorry for all the questions, and thank you again for your response! Most of the time I just change the vinegar every other day (it's done bubbling by then usually). I don't bother coating the teeth that are exposed and I've not had any dreadful consequences... yet. I've had a few teeth fall apart but discovered they were cracked and cemented with limestone. My acid preparation is VERY low tech. 2 Regards, Kris Global Paleo Services, LLC https://globalpaleoservices.com http://instagram.com/globalpaleoservices http://instagram.com/kris.howe Link to comment Share on other sites More sharing options...
OctoDude Posted January 9, 2017 Author Share Posted January 9, 2017 Thank you, Ptychodus04! I greatly appreciate your experience! Link to comment Share on other sites More sharing options...
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