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Posted in response to diamond grease tables from ellie on December 05, 2004 at 07:30:31:

Re: diamond grease tables

Hi Ellie,, To understand how to make a grease table, it is important to understand why they work. Knowing this, it will be simple to build one. First imagine a level window pane whth a tiny bead of mercury on it. Tilt the pane and the mercury bead rolls off without leaving a track behind. In this case the mercury did not wet the glass surface. Now imagine the same experiment but this time using a drop of water on the pane. When the glass is tilted, the water rolls off but this time wets the glass as it rolls, and thus leaves a trail behind. The reason for this is a physical property called surface tension. Surface tension is measured by placing a liquified drop of any material between two probes. The probes are pulled apart until the surface of the drop parts. The force to accomplish this parting is measured by a sensitive machine, thus the surface tension numbers. If the surface tensions of two materials are similar, they will wet each other. If they are dissimilar they will not wet each other.

Now as to diamond,,, the tensions of diamond and water are dissimilar, water will not wet a diamond, even if the diamond is submerged. Water will not wet grease for the same reasons. Place a bead of water on a grease covered plate and it will run off like the mercury did on the glass. Knowing this,, if you make a shallow trough, any dimensions,, and coat the smooth floor with grease like vaseline, you have a grease table. You flow water gently down the slightly sloping trough. The flow needs to be just enough to gently move the sands and small gravel down and out the bottom end. When a sample of material is placed into the trough, the wetted sands and gravels do not stick to the dry but underwater grease surface. However the dry but submerged diamond will stick to the dry but submerged grease surface. As with most processes like this,, the closer you can screen the feed material to the same small size, the better the process works.

Happy trails,, Bill

From William Anderson - December 08, 2004 at 11:01:44

Message: 35148

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Bob Keller