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Techniques for CollectorsOxalic acid - Do's and Dont's

21st Aug 2006 10:40 UTCAymeric Longi

Greetings all !

I have a bunch of cristals that need some cleaning with me, and a pack of powdered Oxalic Acid. This is my first attempt at using it, so would be nice to get a hand. What are the dosages ? Any security measures ?

important thing also, what are the mineral which i should NEVER clean using oxalic acid ?

thanks for help !

Aymeric

21st Aug 2006 21:50 UTCDon Saathoff Expert

First, make sure there is no calcite present in/on your specimen...oxalic acid plus available calcium creates calcium oxalate, in INSOLUBLE ugly yellowish-white coating in/on your specimen. Always test a cleaning liquid on an unimportant sample of your mineral. I use 1/4 cup oxalic to a quart of either distilled or de-mineralized ("RO") water (calcium, again). Use latex/rubber gloves for any 'brush-work' you find necessary. And, there is no panacea here, don't be surprised if you still find yourself doing some "pickin' an' grinnin"!! Keep in mind that oxalic acid IS poisonous if ingested or absorbed through the skin w/ long exposure. PRACTICE CAUTION and have fun tomorrow, too!!

23rd Aug 2006 09:19 UTCAymeric Longi

thanks for your help Don. Should I soak the cleaned pieces in clear water afterwards ?

23rd Aug 2006 09:37 UTCPeter Haas

First of all, you should soak the specimens for about one day in clear water BEFORE applying the oxalic acid solution.

Every specimen will take up liquids through capillary forces. Once these cavities are filled with water, the penetration of any chemical from an outside liquid into the rock becomes negligible (diffusion in a static liquid phase is a very slow process). On the other hand, if the cleaning solution is applied directly, without previous soaking, the solution with all the chemicals dissolved in it will be pulled into the rock. To get rid of them afterwards, by washing with clear water, is almost impossible, since the same principles apply in this situation as in the reverse situation with the chemicals outside and the water inside the rock. In other words, if you don't soak them in clear water before applying the cleaning solution, there will be no use in soaking them afterwards.

23rd Aug 2006 17:02 UTCDon Saathoff Expert

Dr. Haas....thanks for that information!!! I could have saved many good smokey sceptors if I had thought about capillary processes...one more step in the cleaning process!!

24th Aug 2006 11:20 UTCAymeric Longi

wow, that is very important information, thanks a lot Peter !

4th Sep 2006 19:54 UTCPaul L. Boyer

This may be a bit too late for people wanting to know about oxalic acid, but here is the material safety sheet for this compound from JT Baker, a well-known supplier of reagent grade chemicals.

http://www.jtbaker.com/msds/englishhtml/o6044.htm

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