steel vs. clay mold

[jerry keller]

Steel vs clay...that is the question.
I'd like to make a fixture for putting glass onto, that would have a 1-2" post on a base, so I could put a glass piece onto the post.
If it were made from steel, I assume I'd need fibre paper on the steel to protect the glass from the steel.
If it were from clay, it seems kiln wash would be OK on the surface, and it would be good to fire.
Is this correct, and are there any other options?
Thanks

[Brad Walker]

I assume you're talking about making a mold on which to slump or shape the glass. From your question, I'm not sure if you're also planning to slump so that the steel or clay ends up as part of the final glass piece. (If you are, beware of the different expansion characteristics. Expansion can also be an issue with both steel and clay molds.)

Regarding mold materials, either steel or clay can be kilnwashed and used as mold. To kiln wash steel, you need to heat it to around 500F, then apply the wash.

If you use steel, stainless steel is the best choice. Other steels will spall or cause other problems.

If you use clay, you'll need to take the shrinkage factor in account when forming the mold.

Fiber blanket and a rigidizer will also work, as would a number of other refractory products.

If this is single use, you might also consider a plaster/silica mold.

[Tom White]

If you would supply a little more information about the shape you wish to form we might be able to offer suggestions for a mold. In general usage metal forms are better if you plan to drape glass over the top of them because the metal contracts more than the glass as they cool allowing the mold to be removed easily. Clay on the other hand contracts less than the glass and is more suitable if you want to form the glass by slumping into the mold.

Best wishes,
Tom in Texas

[jerry keller]

My thought was to put a bottle onto a post that was on the floor of the kiln, and get the bottle to drape as it will in a minor slumping.
I'mwondering, would a stainless post welded to a plate of steel,if kiln washed, allow me to take the bottle off the mold when the slump was complete?

[charlie]

My thought was to put a bottle onto a post that was on the floor of the kiln, and get the bottle to drape as it will in a minor slumping.
I'mwondering, would a stainless post welded to a plate of steel,if kiln washed, allow me to take the bottle off the mold when the slump was complete?

yes. i might put a round piece of fiber paper on top of the post so that it would be easier to get off the post. you're going to have to have a tall kiln to do this.

[jerry flanary]

You might also true and taper the SS on a metal lathe or maybe a drill press to make it easier to slide back out.