I have experienced problems for some time with rough surfaces on
heavy castings. I was treated by Orchidians to several lengthy and
informative pieces that provided several tips that have been
implemented.
It seems that light and medium weight castings seem to be allright
and do not exhibit surface problems. I recently cast two medium belt
buckles that are considerbly heaver than the successful pieces. The
surface is very rough and details are covered with a fine rough
texture. The surface of the mold seems to have broken down during the
casting process.
In a complete evaluation of my casting process, I discovered that
the vacuum pump induces considerable vibration into the vacuum
casting table and have taken steps to reduce the induced vibration to
near 0. It does not slop around but movement is quite apparent.at the
button before it freezes.
The mold was dewaxed and calcined at 1250 F. The investment was
precisely mixed to the gram of investment and mililiter of water, The
dewaxed flask was cooled and held at 750 F for 30 minutes before
vacuming and pouring the silver. The investment is less than 1 year
old and is stored dry and turned once in a while.
Does it seem reasonable that a heavy charge of liquid silver in a
mold subject to vibrational movement cause the mold surface to
degrade?