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Vacuum cast - investement sucked

Hi folks!

I did vacuum cast for several times now. The results are quite
satisfying, except there is one problem which returns frequently and
I have no idea why this happens: when I put the flask onto the
vacuumtable and set on the vacuumpump, some of the investement is
breaking off and pulled in direktion of the vacuum sucking hole. I
do burn out the flask accurately.

Do you have any clue, what’s going wrong? I atteched two pictures,
that show the situation clearly. Would be glad, to hear your opinion!

Thanks so far,


I perform both centrifugal and vacuum casting. I follow the
directions on the investment and get great results. I primarily use
Kerr Satin Cast II. I have a paper I will share on how to properly
mix you investment and get the proportions exactly right if you would
like for free. There was a great difference in how I do it now and
how I was taught in a class. I have it in MS Word, so you will need
Word to print it out.

Another thing I do is using a drill about 1/8 inch in dia, I drill
holes in the raw investment once it has set up. I drill the holes
right next to the flask and about half way up the flask on the vacuum
side of the flask. I think it helps pull gases out faster. I drill
them about 1/2 inch apart all around the inside parameter of the

I have only had one blowout since I have had the ability to vacuum
cast and I think that time I had a brain burp on the controller and
it got too hot. Okay it may have been operator error. I think it went
in excess of 1300 deg maybe in the 1600 to 1700 deg range.

Let me know if I can help.

Ken Moore
2901 Pleasant Acres Drive

Hi Ken

I am quite interested in your instructions - I use Word. I’d really
be interested in a copy.

For 15 years I taught both centrifugal and vacuum casting in the
Adult Ed Program. Have taken a “breather” (good pun for wearing a
mask with the investment!) - but am planning to have a vacuum casting
class this summer.

Mine is an Aqua-Vac, not made anymore, but a dandy caster! I never
did have a disaster, but I like the idea of drilling the holes. My
measurements were always good, and sticking to the time limit is a
must. The burnout oven is a Neycraft, but manual - that was a pain,
but worked!

Always love the unexpected suggestions that pop up on Orchid.

Rose Marie Christison

i usually mix my investment w/ as little water as possible and i use
hot water to shorten the curing time. try using less water in the
mix or your investment could be old or have gotten some moisture or
been compromised in some way- goo