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Subject: Re: Ahh, good point
Name:
 ludicrous
Date: 4/18/2002 8:13:12 PM (GMT-7)
IP Address: 138.67.48.22
In Reply to: Ahh, good point posted by
Ben
Message:
Here's a possibility:
Start with a brick of soft clay, and some sort of flat-edged, wide-blade utensil (a putty knife?).
Section out a brick in the clay that is the size of your heatsink base. Make many close impressions to the approximate DEPTH of the based, then gradually lift that clay out. Smooth out the interior, and you should have your base.
Now work many parallel slots down into the brick along the length of the base, carefully since the blade will push the clay apart slightly, until you have many thin, evenly-spaced fins. Slowly cut the brick just above the depth of your fins, so that they are all of even height, then re-attach a flat piece of clay by "slicking" both sides with water, and slowly working them together.
Fire the clay in a warm kitchen oven (NOT hot -- you want it less than the boiling point of water so you don't blow the clay apart), until it is completely dry. (This may take many hours.) Then gradually heat the COMPLETELY DRY mold to the 500F (or whatever) limit of your oven, and start working with the silver.
Melt the silver in a crucible, and pour it into the mold. Work fast so that it doesn't solidify between pourings (the hot mold should help with this). Once the mold is filled, shove it back into the oven, and let the silver cool in the 500F oven. AFAIK the heat should help prevent crystal sttructures from forming in the metal. Once the silver has sufficient time to "cool" to the oven temperature (an hour?), turn the oven down by steps, giving it time to cool between each step, and then shut it off entirely.
Once the whole assembly has finally reached room temperature, carefully break the mold away, then mill the base flat...voìla, if you're lucky.
If you do try it this way, I suggest having a fire extinguisher handy throughout this project  The ideal approach would be to find someone who has an old oven hooked up in their garage (as people sometimes do for canning fruits and vegetables in the fall), and work there, as a torch and crucible could be a dangerous thing to have in a kitchen.
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