Hello John B and others: >> If brass numbers are epoxied to marble stone, will >> their different coefficients of thermal expansion >> break the bond?
You certainly went into great detail explaining and calculating the different coefficients of thermal expansion of metal and stone. You concluded that the difference is quite small. It has been my experience that marble, sandstone and limestone contract and expand to a far greater extent based on how much water they contain. These stones act like sponges and absorb large quantities of water, expanding as they do so. While I don't know the exact percentage of expansion due to the absorption of water, the expansion is quite evident to the naked eye. When I make a cut in wet stone with my diamond blades and burrs and then look at the cut the following day, the gap and depth of the cut has shrunk upon drying, requiring me to recut the stone even deeper and wider. The stone sort of "self heals" upon drying. Drying the stone sundial face in the sun and then sealing with dilute polyeurathane prevents water expansion of the finished sundial face. If one decides not to seal the stone, then I would imagine that silicone would be the adhesive of choice since it is so flexible. John Carmichael Tucson Arizona.
