Brian James Maguire Posted July 13 Share Posted July 13 Hi guys i was wondering if anybody could give me advice on acid prep for some of my more delicate fossils , i would love to try it , can it be done without dissolving the fossil as well? Link to comment Share on other sites More sharing options...
TqB Posted July 13 Share Posted July 13 (edited) Not if they're calcite. Silicified stuff works well - I've been doing quite a lot from my local Great Limestone (basal Namurian ) in NE England. Edited July 13 by TqB 1 2 Tarquin Link to comment Share on other sites More sharing options...
izak_ Posted July 13 Share Posted July 13 Do you have any photos of the specimens? Always experiment on an unimportant specimen first if you're unsure if they're silicified or not! 1 Link to comment Share on other sites More sharing options...
Brian James Maguire Posted July 13 Author Share Posted July 13 1 hour ago, izak_ said: Do you have any photos of the specimens? Always experiment on an unimportant specimen first if you're unsure if they're silicified or not! Hi izak, i have done a bit more research and i dont think i can do it on my fossils as they are all silicified, it would be for more bone or teeth etc or where there is a difference between the fossil and the matrix Link to comment Share on other sites More sharing options...
Thomas.Dodson Posted July 13 Share Posted July 13 38 minutes ago, Brian James Maguire said: Hi izak, i have done a bit more research and i dont think i can do it on my fossils as they are all silicified, it would be for more bone or teeth etc or where there is a difference between the fossil and the matrix To be clear, silicified fossils are suitable for acid prep. As TqB mentioned earlier, calcite fossils are not. Do you mean the limestone is heavily silicified? 1 1 Link to comment Share on other sites More sharing options...
Brian James Maguire Posted July 13 Author Share Posted July 13 3 hours ago, izak_ said: Do you have any photos of the specimens? Always experiment on an unimportant specimen first if you're unsure if they're silicified or not! All my fossils are in the album “ Carboniferous ireland” Link to comment Share on other sites More sharing options...
Brian James Maguire Posted July 13 Author Share Posted July 13 57 minutes ago, Thomas.Dodson said: To be clear, silicified fossils are suitable for acid prep. As TqB mentioned earlier, calcite fossils are not. Do you mean the limestone is heavily silicified? Yes the limestone is heavily silcified Link to comment Share on other sites More sharing options...
Brian James Maguire Posted July 13 Author Share Posted July 13 If i was to do a test on a few unimportant bits what acid should i use Link to comment Share on other sites More sharing options...
Kane Posted July 13 Share Posted July 13 A high percentage acetic acid (~80%) might do the trick. Alternatively, you can use caustic potash (KOH: potassium hydroxide), which is sold as flakes. Both processes take some time. Unless you have access to a chemical supplier, it may be tricky to get your hands on the high purity acetic acid, but if you don't mind waiting and swapping out the container every once in a while, most grocery stores sell cleaning vinegar which is rated 10% (about double of normal vinegar one would put on their fish and chips, with the added bonus that you can use it as a household cleaner if you or any in your household suffer from multiple chemical sensitivities). ...How to Philosophize with a Hammer Link to comment Share on other sites More sharing options...
TqB Posted July 13 Share Posted July 13 1 hour ago, Brian James Maguire said: If i was to do a test on a few unimportant bits what acid should i use I've tried both hydrochloric (about 5%) and acetic acid (about 10%) on my silicified stuff and there's usually no difference in results except that the hydrochloric is a lot faster. That said, for a couple of teeth I did use acetic to be on the safe side. The hydrochloric is just patio/brick cleaner which is roughly 10% (they say "less than") diluted 50/50. It can be a good idea to coat the base part of the block with a few coats of rubber solution to provide a plinth (sold for mask making etc.). 1 1 Tarquin Link to comment Share on other sites More sharing options...
cngodles Posted July 16 Share Posted July 16 (edited) On 7/13/2024 at 10:47 AM, Brian James Maguire said: Yes the limestone is heavily silcified If it is silicified, you have a rarer limestone ripe for acid prep. Some of the most incredible fossils to study are from silicified remains. I have black carboniferous (late Pennsylvanian) limestone here, which is not silicified. Acid only dissolves the fossils. The only way to acid-prep calcite fossils is to coat their surface with an acid-resistant/blocking substance, and even that is patient work that is not for me. The only acid-resistant fossils that I can hope to recover are conodonts. The acid pros can prove me wrong, but you should be able to dunk any broken or discarded piece into vinegar and witness the fossils (calcite-replaced shell pieces) dissolve away in a day or two. You get some nice molds or steinkerns if you are looking for that. I have some naturally acid-attacked limestone at the margins here, and some very detailed molds are post-acid. You likely have some brachiopods with spines. The photo below shows what they can look like if they are silicified. Silica minerals replace the original shell, not calcite. I believe the Glass Mountains in Texas have places to recover fossils like these. The name comes from selenite crystals that sparkle at the tops in places. Photo source: https://woostergeologists.scotblogs.wooster.edu/2014/07/18/woosters-fossils-of-the-week-silicified-productid-brachiopods-from-the-permian-of-west-texas/ Edited July 16 by cngodles 1 Fossils of Parks Township - Research | Catalog | How-to Make High-Contrast Photos Link to comment Share on other sites More sharing options...
Brian James Maguire Posted July 16 Author Share Posted July 16 17 minutes ago, cngodles said: If it is silicified, you have a rarer limestone ripe for acid prep. Some of the most incredible fossils to study are from silicified remains. I have black carboniferous (late Pennsylvanian) limestone here, which is not silicified. Acid only dissolves the fossils. The only way to acid-prep calcite fossils is to coat their surface with an acid-resistant/blocking substance, and even that is patient work that is not for me. The only acid-resistant fossils that I can hope to recover are conodonts. The acid pros can prove me wrong, but you should be able to dunk any broken or discarded piece into vinegar and witness the fossils (calcite-replaced shell pieces) dissolve away in a day or two. You get some nice molds or steinkerns if you are looking for that. I have some naturally acid-attacked limestone at the margins here, and some very detailed molds are post-acid. You likely have some brachiopods with spines. The photo below shows what they can look like if they are silicified. Silica minerals replace the original shell, not calcite. I believe the Glass Mountains in Texas have places to recover fossils like these. The name comes from selenite crystals that sparkle at the tops in places. Photo source: https://woostergeologists.scotblogs.wooster.edu/2014/07/18/woosters-fossils-of-the-week-silicified-productid-brachiopods-from-the-permian-of-west-texas/ Thank you so much for such a detailed and useful post, i will be doing some experimenting shortly when i get my holidays from work and will let you know how i get on Link to comment Share on other sites More sharing options...
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