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N8 · 02-26-2003, 07:44 PM

I can tell you a truly subjective, non-critical way to measure the flatness. IF you do have a granite flat with the correct paper work to authenticate it's degree of flatness (and your granite flat is in near perfect shape still), you can get a rough estimate of how polished-flat your surface is by how hard it is to pull it back off your granite flat.

Notice I said 'polished-flat'. You can have a really flat surface that is not polished, but it will not suction-adhere to the polished surface of the granite flat. You need two very flat, polished surfaces. I have had polished-flat surfaces stick together that required me to pry a razor blade under them to get them off my granite flat. Remember, this is only an estimate, and gives you no real data. It is purely subjective, but does give you an idea of how polished-flat your surface is. This is just air (lack of air) suction between the surfaces.

You could try this with glass, but glass is not as flat as a good granite flat, plus glass breaks. Glass is really not very flat (in the scientific sense.) One side of a piece of glass is pretty wavy, the other is flatter. Has to do with the way they make glass.

02-26-2003, 07:44 PM	#35
N8 Cooling Neophyte Join Date: Sep 2002 Location: Pullman, WA Posts: 91	I can tell you a truly subjective, non-critical way to measure the flatness. IF you do have a granite flat with the correct paper work to authenticate it's degree of flatness (and your granite flat is in near perfect shape still), you can get a rough estimate of how polished-flat your surface is by how hard it is to pull it back off your granite flat. Notice I said 'polished-flat'. You can have a really flat surface that is not polished, but it will not suction-adhere to the polished surface of the granite flat. You need two very flat, polished surfaces. I have had polished-flat surfaces stick together that required me to pry a razor blade under them to get them off my granite flat. Remember, this is only an estimate, and gives you no real data. It is purely subjective, but does give you an idea of how polished-flat your surface is. This is just air (lack of air) suction between the surfaces. You could try this with glass, but glass is not as flat as a good granite flat, plus glass breaks. Glass is really not very flat (in the scientific sense.) One side of a piece of glass is pretty wavy, the other is flatter. Has to do with the way they make glass.