I have experienced casting defects and don’t know the reason.
Using high grade investment purchased in 2003 and stored in
carefully fastened plastic bag in a plastic pail bucket, the sterling
belt buckle casting was defective.
The casting exhibits a rough texture on surfaces that should have
been flat and smooth.
The molded investment surface seemingly broke down and the resultant
casting surface is rough over 50% of the total surface.
The 38/100 mixing ratios were carefully followed measured to the
gram. The water was pure rain water. The temperature was a little
cool with investment setting time ~ 15 minutes in a 65 F room.
The flask was burned out completely with the opening being white
with no trace of carbon. The flask was ramped to 300 f then 700 then
1350 and cooled to 850 and soaked for half an hour. The total cycle
was 5 hours. The burnout began approximately 16 hours after
investing. The invested flask was stored at approximately 45 F
The flask was not dropped or jolted. The sprues were not tightly
bent. The casting is 66% new metal. The flask was cast with a good
solid 30 im on the vacuum gage
Although the soak temperatures are published, the ramp times are
not. Heating too rapidly is a cause of defects. Are there suggested
ramp times to 300, 700, 1350, cooling to 850?
Smaller castings with same investment and similar procedures but
lacking the extensive flat surfaces of a buckle don’t have the noted
Orchidian thoughts as to cause for the defects would be appreciated.