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Investment mix - Hardening time

Hey guys…

Ive been wondering about it for quite a while now since I wanna optimize my time when doing lost wax casting.

When i’ve mixed, vacuumed etc etc. I usually let my mold sit for 1.5 - 2 hours before putting it in my kiln to do the burnout…

However, is there a limit to how long is prefferable to let my mold sit? Can i leave it over night and start the burnout next morning.

Heard that it’s good to have the moisture in the investment since it helps to push out the wax, and it has therefore been my concern if its bad to let it harden too long if all the moisture dissapears?

Best Regards William

Hi William, that is my usual way of casting. I invest in the evening, usually after a long day of preparing waxes, and start the burnout the next morning.

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You can/should leave it overnight. Having moisture in the investment does indeed push the wax out but it also leaves a more grainy texture and adds nothing of value to the burnout.

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Sounds good, Thank you so much for the reply! This really gives me a lot of freedom that I dident have before! :hear_no_evil:

Thank you so much for sharing, and even adding additional knowledge to my question! I’ve been experience some slight grainy texture on my previous cast.s

Actually just casted my best casting so far, which i probably owe to letting the mold sit over night!

Soo stoked!

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Thanks much for these posts. I was also taught to let the invested flask sit for exactly 2 hours (and that’s consistent with the investment instructions as well) before putting the flask in the kiln. It’s a killer because it stretches my casting days an extra 2.5 hours longer. I will definitely try this!

Not trying to be contentious but without knowing what the burnout ramp and soak cycle is being used it is hard to make an informed statement. I normally use an overnight very slow burnout cycle regardless of how long the canister has set after investing.

I can believe the drying time would make a difference if a constant temp burnout is employed without a ramp and soak cycle.
Regards RLW

I always thought some of the concern about letting the flask dry out is that the investment will start to crack internally and you might see finning on some of your pieces.

I usually prefer to have it sit for 4-6 hours before I cast and like others, invest in the evening/night and burn out in the morning so I can cast by the following evening.