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Hello all, Me and my friend would like to start practicing chemical preparation. Neither of us have done that before. We were mainly wondering what types of commercially available fossils are fit to practice this on? I know of limestone fossils like Keichousaurus, but that seems quite expensive for a first try. Neither of us lives close enough to a fossil location to reallistically obtain this way. So I tried to make a list of items that are not too hard to find unprepared. My friend has quite a bit of experience with working with chemicals, but doesn't know what chemicals would work with what rocks. It has also never been my strong side. Do you think chemical preparation would work on any of these fossils? -Schlaifhausen ammonites blocks -Khouribga fossils (don't think I've ever seen chemical preparation on this) -Spirifers from Barvaux, Belgium (been here a couple of times so have quite a few of those) Would love to hear more suggestions if anyone has any? We do not have the room to afford the other tools for mechanical prep, hence why we want to try it this way.

I am writing a short manual on preparation methods for our club and I am including a short section on chemical preparation. This is most commonly done with acids on carbonate rocks. For many newbies, chemical preparation is attractive since all you need is a weak acid that everyone has in their kitchen (vinegar or lemon juice) and don't have to buy expensive equipment. I try to avoid it if at all possible since it works on a very narrow class of matrices, you have relatively little control over it, you may dissolve the fossil itself if it hasn't been silicified and its irreversible. Consequently, I don't have much experience with it. I have tried brushing Muriatic Acid (concentrated HCl) on limestones and immersing them in weak acids like household vinegar with mixed results. I have a few questions: does acid preparation only work on carbonates (limestone CaCO3, dolomite CaMg(CO3)2 or siderite FeCO3) or are there other fossiliferous matrices that can be prepared using acid? Are there other legitimate ways to prep using acids other than brushing it on or immersing a fossil in a weak solution? I am aware of using organic solvents to prepare tar pit fossils, but this is something outside of most amateurs. Are there other chemical preparation methods other than organic solvents on tar pits or acids?

I was interested in the process of cementation bivalves use to attach. I used the internet to research and couldn't come up with much information. I don't know if I am using the right search terms or if there isn't that much information. I thought this was the best avenue to find the answers. Maybe @doushantuo could help but any help would be appreciated!

PART 1. Greetings all, it has been quite a while since I've posted here. I recently purchased some potassium hydroxide (KOH) flakes from Amazon for fossil preparation purposes. I was told about this chemical as a substitute as Quaternary-O by my friend Gabe Ward. This stuff is basically a really strong base that works (I think) through oxidizing ogranic compounds in a rock. This makes it particularly effective on shales and siltstones, but not so much with most limestones, especially crystalline varieties. I wanted to write a post about this stuff because it seems like it has the potential to be a cheap alternative to air abrasion or scribing in some cases. Safety: The first thing to know about KOH is that it is a pretty powerful base, meaning this stuff is pretty hydroscopic and reacts readily with water. It is very toxic, and eye-wear and gloves should be worn when handling. Don't allow this stuff to make contact with your skin. I am a bit lax with how I handle it, and have gotten it on my arms on one occasion. You don't feel it at first, but after several minutes you will feel it burn and blisters will develop. It seems to have even burned off some of the hairs off where it made contact. This was pretty minor, seeing as I caught it, all burning and blisters went away about half an hour after washing it, but this should give you an idea of what it can do. The container on my KOH says that it produces fumes. I've noticed no ill effects, but it's something to keep in mind. This is all I wanted to do regarding safety, just give an idea of what this stuff can do. Usage: The potassium hydroxide I purchased came in the form of pellets. I apply it by taking tweezers and placing the flakes on the matrix covering the fossil. When left out, the KOH will react with water in the air and start to dissolve. During this time it reacts with the matrix, and you may depending on the lithology, see some evidence of the reaction during this time. Depending on the reaction speed, I may leave the fossils out for one to eight hours. Here is one example, a set of Pentremites conoideus from the Somerset shale fm. of Kentucky. The photos aren't great, but hopefully illustrate what this stuff can do. These are separate specimens, but the one on the left illustrates a very similar "before" condition, that the one on the right was in. My next reply will address some adverse effects, and some other thoughts.