On Jan 10, 9:27*am, "Maxwell" #$$9#@%%%.^^^ wrote:

How can you mold or sculpt invest foam articles with a simple hobby process,
and then get something as detailed as air cooled fins on a foam or wax
investment to withstand even the most careful ramming process for green
sand, oil sand or air set casting?
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Dear Maxwell,

While there are some pretty sturdy plastic-like waxes that can
withstand ramming-up in a core box, most of the methods using lost wax
begin by DIPPING the wax model in a slurry of high-temperature CLAY,
after all of the sprues, vents gates and supports have been attached
manually. After the clay dries it is BAKED, first at a fairly low
temperature ( ie 200F ), during which it is rotated several times to
get rid of the casting wax, and finally at a higher temperatures, such
as 500F for about two hours. The resulting product is then stiff
enough to withstand ramming.

There are variations to this theme. Some call for several dipping &
baking episodes using different recipes of clay. Dentists are the
best source of information on this procedure. The main down-side is
the HIGH COST of the refractory clay dips.

-Bob