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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.