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Wax Fabrication for Lost Wax Casting - Questions

Our club is recently reviving lost wax casting. Equipment has been upgraded and beginning classes are underway. I have several questions owing to our recent experience.

1 - A fair number of beginning projects are having issues with filling the cavity completely. The project was a single pre-cast wax ring in a single small casting flask - not multiples on a tree. Basic cylindrical rings casted well. Signet-style rings all had serious issues.

While there were no issues during fabrication using the pre-cast rings (we just added sprues), a key blame is being placed on the wax as being “old”.

While the variety of wax material (rings and sprues) are up to 10 - 20 years at most, all are pliable, melt well, and do not crack. (e.g., has not melted or has not crystalized). The fix is proposed as throw out all wax and buy a complete new supply. As the ‘old’ wax has not been tested against new wax, I’m anxious about this as the sole issue.

Can others point to issues with old wax that we should be aware of?

2 - I suspect a key issue is improper or inadequate spruing. (We’re all beginners.) Can folks suggest an excellent book or two that give practical information on spruing for different scenarios?

Many thanks to everyone!

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Rather than use centrifugal casting, you might look at sand casting. Craig Dabler’s DIY Castings Group fb should get you started. It’s far less scary and cheaper to do. He has totally changed how sand casting works. Nice not grainy results. You can cast from waxes and many other things. Just a thought.
Judy Hoch

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I recommend Practical Casting By Tim McCreight, it tells you everything you’ll need to know.
Happy casting and healthy sprues to you!

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I don’t think the wax is the issue. Do you have adequate sprues? Have you made a paste of the investment to paint on and fill more intricate areas before filling the flask? Is the investment the right consistency? Was your silver fluxed and heated to the right temp for the casting process?
Did you properly weigh for the right amount of silver to fill the space? Did you have the right amount of rotations enough centrifugal force?
These questions are important before questioning the wax. And one more reminder, it’s cast, not casted.

I agree with Pbkaren. I think you needed to add sprues to signet rings and make sure you have the proper amount of metal. Also, sprue failure can be an issue. I use “Perfect Purple” to attach my wax sprues to both the piece and the main sprue. I tried just melting the sprue wires, but some of them would partially detach during investing and vacuuming. It’s expensive, but worth it. I use wax that is really old and haven’t had problems with it.

Thanks all for the replies and sorry fro late reply of mine.

The group did some checking and found 2 issues - which I ssupected.

1 - Bad seal resulted in poor or no vacuum. THus gravity fed only.

2 - The amount of silver was incorrectly calculated and so could not fill even if sufficient vacuum.

Thanks for the Perfect Purple recommendation - looking into that!