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11 minutes ago, CactusPots said:

I wouldn't rely on a head stock alone.  I'd want a tail stock supporting the blank.  Plaster doesn't have the strength, I think, to be gripped by a jawed head stock the way metal or wood could.  Definitely wouldn't hold screws.  Let us know how it works out.

I still don't get why.  What can you make by turning that can't be a thrown form?  Rae's comment about using the turned form to make a silicon mold to cast plaster is giving me brain freeze.  You're making a plaster cast of a plaster model?  The only reason I can think of is if you want a slip mold ultimately, but have no access to thrown forms.  We are assuming clay is in here somewhere, right?

People turn plaster for making masters for casting.  Although a lathe isn't required, have seen plenty of people turn plaster on a wheel.

You can cast a silicone master afterward that doesn't have the same durability issues that plaster does, in case this is a form you want to cast for years to come.  

As to why plaster instead of clay, plaster is smoother and stronger than clay when making a mold, doesn't deform, etc.  It's a tradition in France and other regions in Europe.  It's also easier to be more exact than when throwing clay.

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On 3/1/2020 at 3:40 PM, CactusPots said:

I wouldn't rely on a head stock alone.  I'd want a tail stock supporting the blank.  Plaster doesn't have the strength, I think, to be gripped by a jawed head stock the way metal or wood could.  Definitely wouldn't hold screws.  Let us know how it works out.

I still don't get why.  What can you make by turning that can't be a thrown form?  Rae's comment about using the turned form to make a silicon mold to cast plaster is giving me brain freeze.  You're making a plaster cast of a plaster model?  The only reason I can think of is if you want a slip mold ultimately, but have no access to thrown forms.  We are assuming clay is in here somewhere, right?

I have some silicone molds that were produced to make ice sculptures. Couldn't use them for clay, but I did cast a nice plaster leaping trout!

Edited by Rae Reich
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  • 7 months later...

I work with wood and ceramics, and am looking to get into making masters/models/positives out of plaster on my woodturning lathe as well. My plan is to turn a "plaster chuck" out of wood, then pour the plaster cylinder blank directly onto that. The pics I've seen of plaster chucks seem to just be shallow bowls on one end (the plaster end) and a tenon on the other end that your lathe can grab onto. I'll try drilling some pits or carving some grooves into the bowl to give the plaster more to grab hold of. I'm also planning to add 1/4 cup of pva glue to the water I mix my plaster with, as I've seen it recommended for strengthening casting models. One point, I'm pretty sure you would want to work at a lower rpm with plaster but I'll figure that out as I go. Might not work at all, we'll see! This thread is several months old, so if anyone's followed through I'd love to read about any lessons learned.

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Just to mention turning boxes where you mainly turn wet/setting plaster against a profile.

TurningBox.jpg.8b549784f30155847c9bf2bc8fe601a4.jpg

This is FIGURE 6.5.1-E Plaster turning box with a profile of a vase to be modeled.
From Forming Techniques for the Self-Reliant Potter  https://tinyurl.com/y5y6keh9

This is a wooden frame which is fitted with a metal shaft that can be rotated by a hand crank. It is used in combination with a profile. The metal shaft is first prepared by wrapping it with paper or cloth, and providing it with a metal pin. The paper prevents plaster from sticking to the shaft, and the pin is fixed so that it keeps the plaster from spinning freely while working, but it can be removed when finished so the plaster can slide off the shaft. Plaster is first built up on the shaft by applying it and rotating at the same time. When it is a little smaller than the profile, more plaster is applied, and the profile shapes it to the final form. WARNING: This seems like a simple device, but in fact requires a lot of skill to operate correctly. It is not recommended unless you can find an experienced person to teach you

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