John H. Rodgers on thu 5 mar 98
-- [ From: John H. Rodgers * EMC.Ver #2.5.02 ] --
Thin, lightweight, strong shells can be made using fiberous materials in the
plaster. Someone mentioned using open-weave burlap. I often use hemp fiber.
This is some of the toughest stuff ever. It is what the Navy used to have
all of its ropes and hawsers made from. Available from Polytek (on the WWW).
I first coat the model with the plaster to get the detail, then mix another
batch, then (1)place the fiber over the plaster coated model, and work the
fresh wet plaster into it by hand, or (2) add the fiber to the fresh plaster
batch, mush it around until coated and soaked, then apply to the surface.
When all has set, I immediately apply a finish coat to smooth things out.
I use these methods when making the bigger molds.
John Rodgers
In Alabama
Grace Liu on sat 7 mar 98
John H. Rodgers wrote:
>
> ----------------------------Original message----------------------------
> -- [ From: John H. Rodgers * EMC.Ver #2.5.02 ] --
>
> Thin, lightweight, strong shells can be made using fiberous materials in the
> plaster. Someone mentioned using open-weave burlap. I often use hemp fiber.
> This is some of the toughest stuff ever. It is what the Navy used to have
> all of its ropes and hawsers made from. Available from Polytek (on the WWW).
>
> I first coat the model with the plaster to get the detail, then mix another
> batch, then (1)place the fiber over the plaster coated model, and work the
> fresh wet plaster into it by hand, or (2) add the fiber to the fresh plaster
> batch, mush it around until coated and soaked, then apply to the surface.
>
> When all has set, I immediately apply a finish coat to smooth things out.
>
> I use these methods when making the bigger molds.
>
> John Rodgers
> In Alabama
John and otheres who've tried this mould-making method,
Would these kinds of lightweight moulds work for slip casting? If I
understand correctly, the reason why the mould is lightweight is due to
the fact that you can make the mould much thinner than a conventional
mould (without burlap or hemp). If this is the case, then my guess is
that this method wouldn't work too well for slip casting as you would
need the larger mass of plaster to absorb the water from the slip. Yes?
TIA for any comments.
Regards,
Grace
John H. Rodgers on sun 8 mar 98
-- [ From: John H. Rodgers * EMC.Ver #2.5.02 ] --
Grace, when I have used the fiber in the mold for strength, it has mostly
been for molds where the clay will be pressed in. Usually to lighten the
weight of a mold to be used for slip casting the mold is designed to have
areas cut away so there is no excess plaster present tho ad to the toal
weight. Best example I can give, would be like a cylinder mold. The mold
would be first cast in a square form, then the plaster forming the corners
would be cut away so that the contour of the outside of the mold would more
or less conform to the curve of the inner shape, ie the outside would be a
cylinder too. With that approach in mind, to eliminate excess weight and
material consumption, mold makers often produce some strange shaped molds.
You might want to make a mold that has a 1/2 inch surface shell directly
against the model, then on that shell, use hemp or burlap and build it up
just a little more for added strength., then give the mold a try at slip
casting. It may surprise you.
Something you might want to try is to first weigh your pouring bucket and
get the bucket weight or tare. Then weigh your slip bucket with slip in it,
then subtract the bucket tare, getting the weight of the slip without the
bucket. Next pour your slip, completely filling the mold. Weigh the bucket
again. When the mold is ready, drain all excess slip back into the bucket.
Weigh the bucket again. At this point you know how much liquid clay slip was
actually used in forming the greenware shell.
When the mold is opened, weigh the newly formed greenware piece. The
difference in weight between the liquid clay after draining and the weight
of the piece right out of the mold, is the weight of the water absorbed by
the mold. You can get a good indication of whether or not the thinwall mold
is doing its job.
John Rodgers
In Alabama
-------- REPLY, Original message follows --------
Date: Saturday, 07-Mar-98 11:01 AM
From: Grace Liu \ Internet: (asianera@netvigator.com)
To: Clayart \ Internet: (clayart@lsv.uky.edu)
Subject: Re: lightweight plaster molds - Revisited
----------------------------Original message----------------------------
John H. Rodgers wrote:
>
> ----------------------------Original message----------------------------
> -- [ From: John H. Rodgers * EMC.Ver #2.5.02 ] --
>
> Thin, lightweight, strong shells can be made using fiberous materials in
the
> plaster. Someone mentioned using open-weave burlap. I often use hemp fiber
..
> This is some of the toughest stuff ever. It is what the Navy used to have
> all of its ropes and hawsers made from. Available from Polytek (on the WWW
).
>
> I first coat the model with the plaster to get the detail, then mix
another
> batch, then (1)place the fiber over the plaster coated model, and work the
> fresh wet plaster into it by hand, or (2) add the fiber to the fresh
plaster
> batch, mush it around until coated and soaked, then apply to the surface.
>
> When all has set, I immediately apply a finish coat to smooth things out.
>
> I use these methods when making the bigger molds.
>
> John Rodgers
> In Alabama
John and otheres who've tried this mould-making method,
Would these kinds of lightweight moulds work for slip casting? If I
understand correctly, the reason why the mould is lightweight is due to
the fact that you can make the mould much thinner than a conventional
mould (without burlap or hemp). If this is the case, then my guess is
that this method wouldn't work too well for slip casting as you would
need the larger mass of plaster to absorb the water from the slip. Yes?
TIA for any comments.
Regards,
Grace
-------- REPLY, End of original message --------
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