Thank-you for the responses regarding my investment casting fail.
So, I’ve learned the following:
Investment powder is likely to degrade if old or allowed to pick up
moisture. So, I’ll stop buying those small lots of investment that
come in baggies that originate from larger packages broken down by
The mix ratio of water to powder has to be exact, no more adding
just a little more water to make it easier to pour.
The flask must be perfectly still while “glossing off”; the
investment is beginning it’s initial set and any slight motion will
degrade the strength of the cavity.
Allow enough time for the flask to set after pour to give it some
strength before burn-out.
Ramp up the inital temperature in the kiln from zero to 300. I was
putting the flask in at 300-400.
Gradually ramp temperature from 300-1350. I may have gone over 1350
so that may have contributed to the cracks in investment. I also have
to check that temperature guage on the kiln for accuracy.