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Hello, i have a few fossils like the one in the picture, they are all shells in limestone. I want to clean them and i have had some success with acetic acid. I just wondered if someone had any tips or a better way to clean them, also if anyone knows whats the best concentration to clean them, mine is 25% acid but this seems a little high. I can post a picture of a relatively clean one if it helps to identify the best way to clean them.

fossil.PNG

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I wonder if you might have better luck using potassium hydroxide flakes (KOH). I'm not sure about the chemical composition of the material you are working with, so I would advise doing some research first before potentially ruining good specimens using the wrong agent. Chemical cleaning can be a fairly lengthy and repetitive process. It may be more efficient to look into air abrasion. 

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You want to use 5% acetic for fossil prep. It will go much slower but the acid is less likely to etch the fossils.

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1 hour ago, Ptychodus04 said:

You want to use 5% acetic for fossil prep. It will go much slower but the acid is less likely to etch the fossils.

What is the general guideline , using either KOH or acetic acid, for when to refresh the flakes or solution? If left in for days, it seems the acid or base would be neutralized. Silly question that may not have real answers!!!

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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2 hours ago, minnbuckeye said:

What is the general guideline , using either KOH or acetic acid, for when to refresh the flakes or solution? If left in for days, it seems the acid or base would be neutralized. Silly question that may not have real answers!!!

 

KOH is good for clay based matrices. Acid for most others. I add KOH flakes every day. Cover the specimen, let it react, next day, rinse and repeat.

 

Acid prep is more involved. Soak for a day, soak in water for a day, dry the specimen, coat exposed bits with Paraloid, repeat until desired prep is achieved. The main thing with acid prep is to remember to soak in clean water at least as long as the time in the acid. There’s more to acid prep but that’s the general nature of the process.

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3 hours ago, minnbuckeye said:

@Ptychodus04, do you change the acetic acid each time you rinse?

Yes

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