Hi Jim, #1…Only GOD is perfect. #2…I am your (the artists)
servant. #3…I have found (after many years and thousands upon
thousands of castings) that 90% of the solution is spruing. We at
J.A. Henkel Co.,Inc. are so engaged with this notion that the
by-line of our ad in Metalsmith magazine reads “Taming Of The
Sprue”. Get a pair of degree calipers. Measure every spot on your
wax. Draw a map. You will see some areas that are thicker than
others. You need a sprue at each of these “Hot Spots”. Use a
sprue that is slightly (.2mm-.5mm) thicker. You may have
several. Try to keep them to about 3/4" and gather them to one
spot. Weld them to a plug of wax that is slightly larger than the
bundle of sprues. Make the plug as high as it is wide. Weigh this
assemblage for your usual wax to metal ratio. Add 15g for gold
and 25g for silver. If you are using hard carving wax, your first
burn-out temp stage should be 200F for 3hrs (I know, all the
books don’t say this, neither does Kerr, but it works!).
Everything else is common sense: clean crucible, clean metal(50%
new), clean everything!, new investment, etc. J.A.