Sandstone dust has a very salty taste. Does that mean I should dip my stone blanks in acid before I engrave them to protect them from further erosion? A scary thought!
When stone masons lay flagstone flooring, they often clean the unwanted calcium carbonate deposits off the stone using dilute sulfuric acid and a scrub brush. But I have always been afraid to use H2SO4 on my stones, fearing that it might damage the stone internally or cause the sedimentary stone layers to separate. I worry that this possible damage might take years to show itself. (But I observed no immediate damage to the stone when I experimented with H2SO4, and it did do a very good job of cleaning the stone.) So you also have to be a chemist to make sundials, huh? John John L. Carmichael Jr. Sundial Sculptures 925 E. Foothills Dr. Tucson Arizona 85718 USA Tel: 520-696-1709 Email: [EMAIL PROTECTED] Website: <http://www.sundialsculptures.com> ----- Original Message ----- From: "Edley McKnight" <[EMAIL PROTECTED]> To: <[email protected]> Sent: Tuesday, October 29, 2002 5:34 PM Subject: Re: Eroded rock > Hi Dialists, > > Awhile back, researching machining on vitreous ceramics, I came upon the statement > that most rock/ceramic surfaces have a much lowered surface strength when the > surface was alkaline and a much greater strength when acidic. (It was in a NASA > report, but I don't remember the number ) Experiments showed that indeed drilling > speed was up to 7 times faster on alumina ceramics while in a solution of a mild > base such as borax than on a neutral surface. A mild acidic solution such as boric > acid doubled the time of drilling. Shear testing and microcrack examination showed > that the acid surface actually was both stronger and healed many microcracks. Even > mild acetic acid made a great degree of difference. > Shaping with sand-blasting obeyed a simular effect. i.e. The surface chemistry of > the etched lines and their surrounds may be acidic enough to hold up to erosion > longer. > > Just a thought. > > Edley McKnight > > - > -
