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Green Soap And Drape Molds


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I am trying my first experiments using a drape mold. 

 

There seem to be a number of options:

1. Bisque the mold then lay the clay over it

2. Bisque the mold then rub a layer of green soap on it before laying the clay over it

3. Fire the mold to glaze temp with no glaze then lay the clay over it

4. Fire the mold to glaze temp with no glaze then rub a layer of green soap on it before laying the clay over it

5. Fire the mold to glaze temp with glaze then lay the clay over it

6..Fire the mold to glaze temp with glaze then rub a layer of green soap on it before laying the clay over it.

 

 

What are my trade offs for these strategies? Or is there a better way to go? Or????

 

Thanks

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You want your mold to absorb some of the clay moisture so the clay holds its shape. So, that puts you in the bisque options -- more porous than firing the mold to glaze temps which would be more vitrious and less water absorbent. And, I'd forgo any glaze -- that would preclude any absorption from the mold. I don't see a need to use soap or mold release, either, on a bisque mold. I'm partial to #1. What is important is the claybody used for the mold. If you want a smooth clay surface, use a smooth clay body for the mold; if you like some texture, grain, then use a clay body with some grog or sand to give a rougher feel.

 

Other options are plaster, wood, and the pink/blue house siding insulation from Lowe's or Home Depot. The insulation can be formed with surforms, knives/saws, and sanded.

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If you are talking about a bisque mold form then you should be able to just drape the clay over it with no soap or prep. You just have to watch out and get the clay off when it is set up but not yet shrunk enough to crack.

 

Actually, if you are only going to use the form a few times you don't even have to fire it. Just make your shape from solid clay, let it surface dry a bit and use. When done, re hydrate and use the clay.

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Whenever I make a mold from plaster I coat the surfaces of object and clay 1/2 with green soap or mold release like pure lube from Laguna/axner. If pouring plaster into metal bat tins I use green soap.

If your mold is made of clay just bisque it and drape it.

I prefer slump molds over hump molds as it srinks away(does not crack) and does not need as much monitoring as a hump mold.

Mark

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I use Murphy's Oil Soap which you can buy at the grocery stores. Comes in a spray bottle, so you just spray the plaster mold or wooden cottles with it.

I wouldn't use any soaps or release agents on a bisque mold-too messy.

TJR.

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I am trying my first experiments using a drape mold. 

 

There seem to be a number of options:

 

 

 

What are my trade offs for these strategies? Or is there a better way to go? Or????

 

Thanks

 

 

Option 7 - cover the mould with two layers of cling-film/dry-cleaner bags before humping.  Layer 1 sticks to the mould, layer 2 sticks to your clay, and they can be separated easily.  This way you can use moulds made of anything.  Only issue is you will get creases on your clay unless you can stretch/drape layer 2 carefully.

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Whats so special about this soap? I use any oil that is to hand.

 

As I understand the original craft process.

Real soft soap (i.e. the more soluble potassium soap as found in potter's soap) applied in

the old-fashioned multi-coat way reacted with plaster surfaces to form a thin layer of calcium

stearate (calcium from the plaster and stearate from the soap). This was reputedly particularly

effective in preventing fresh plaster adhering to old plaster.

 

Personally I use a 50:50ish mix of Fairy Liquid and water when casting plaster moulds for slip-casting.

It's ready to hand and works well enough.

 

Perhaps the old mould makers (with their extensive use of both plaster masters and block moulds) had

larger plaster-to-plaster surfaces to worry about -- or needed to achieve higher standards of finish.

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Oh, can really tell who's a brit by the language in some of these posts. Chilly's comment about what she does with molds/moulds I'm not touching, fairy liquid is dishwashing liquid for anyone who's unsure of this term for it. 

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Oh, can really tell who's a brit by the language in some of these posts. Chilly's comment about what she does with molds/moulds I'm not touching, fairy liquid is dishwashing liquid for anyone who's unsure of this term for it. 

I'm not British. I'm Canadian.The pros use Green soap. Who knew why. I prefer yellow soap myself.

T.

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about a hundred years ago when i was first buying pottery supplies, i got a bottle of green soap.  i think it is still on some shelf somewhere, never opened, never used.  i did notice that it separated into layers inside the bottle.  do you think i should sell it on ebay?

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  • 2 months later...

I use WD40 on non absorbent surfaces so clay doesn't stick, mainly thing like cookie/tile cutters.  Never used it when making moulds.  

 

The best advice I have seen is in the book "The Essential Guide to Mold Making & Slip Casting (Lark Ceramics Books)where they list various model materials and what to use as mould release.

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  • 2 months later...

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