I have it sealed tightly, but suspect that it has still absorbed
moisture. I ended up with fins on edges of casting. I never had
this unless not measuring H2O and weighing investment. I am pretty
sure the issue is not metal or alloy. I'm stumped
It it sets up properly and solidly, in an appropriate amount of
time, then likely the investment is still OK. You might try to seal
the container, and roll it around a bit, to make sure the mix of
componants is still uniform. Investment can sometimes settle out
unevenly (especially in shipping, I was told), so rolling it around
to make sure it’s a uniform mix, can help.
Also, I prefer to weigh both the investment AND the water, rather
than measuring the water in some graduated container. Weighing is
more accurate. Pay attention to water temperature, and how it relates
to gloss off time. If it sets more slowly than it should, then
perhaps the investment isn’t so good any more.
Also, I’d suggest allowing the invested flask to set, quietly, for
at least two hours or more, before starting the burnout. That allows
it to reach full strength.
And skip the debubblizer. It can cause as many, if not more,
problems than it claims to solve. Also take care if using those
“orange oil” wax cleaners. If not totally dry and clean, those can
really screw up some investments. Personally, I don’t take a chance
with them any more. The platinum investments seem especially weakened
by that stuff, causing very rough surfaces if it’s at all still wet,
or even if there’s too much and fully dry.
And try to use a slow temperature rise during at least the first 400
degrees F of the burnout cycle. If you don’t have a programmable
burnout controller, set the furnace so it takes at least an hour or
so to get those first 400 degrees. Crystobalite undergoes a
structural change within that temperature range that causes an
expansion to take place. If the flask is rising in temp too fast,
this can be uneven, resulting in increased risk of cracking, which is
what it sounds like you’re getting. Also, don’t use a larger flask
size than you need. Smaller flasks are more forgiving of overly rapid
temperature changes.
And finally, if you’re still unsure whether the investment is good
or not, and don’t have the time or energy to fuss with
troubleshooting it, there’s the other simple solution. Get a new
container. fortunately, the stuff isn’t as pricey as metals have
become. Use the new for “important” flasks, and save the old stuff
for things that might not be as important to have them come out
perfect. In my shop, that might include things straight from rubber
molds, with little labor in the wax, so if it doesn’t cast, one just
shoots another wax from the mold and does it over…
Hope that helps.
Peter Rowe