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plaster-msg - 3/17/99


Use of plaster in period. References. How to use.


NOTE: See also the files: casting-msg, frescoes-msg, painting-msg, tiles-art, pottery-msg, block-printing-msg, masks-msg.





This file is a collection of various messages having a common theme that I  have collected from my reading of the various computer networks. Some messages date back to 1989, some may be as recent as yesterday.


This file is part of a collection of files called Stefan's Florilegium. These files are available on the Internet at: http://www.florilegium.org


I  have done  a limited amount  of  editing. Messages having to do  with separate topics  were sometimes split into different files and sometimes extraneous information was removed. For instance, the  message IDs  were removed to save space and remove clutter.


The comments made in these messages are not necessarily my viewpoints. I make  no claims  as  to the accuracy  of  the information  given by the individual authors.


Please  respect the time  and  efforts of  those who have written  these messages. The  copyright status  of these messages  is  unclear at this time. If  information  is  published  from  these  messages, please give credit to the originator(s).


Thank you,

    Mark S. Harris                  AKA:  THLord Stefan li Rous

                                          Stefan at florilegium.org



From: ALBAN at delphi.COM

Newsgroups: rec.org.sca

Subject: Plaster of Paris

Date: 13 Mar 1998 22:58:17 -0500


Constance De LaRose said

>I learned that the most common ceramic form material used is

>plaster of paris.  Guess what, plaster of paris is out of period so

>it was back to the research to learn that they used porous

>earthenware molds.  


Not that I would ever suggest that someone not do research on

better materials for mold making, but, um, er, Constance? Plaster

of Paris _does_ seem to be period:

General reference: The Encyclopaedia Britannica, 15th ed. (1981),

vol. VIII, p. 30: "Used since ancient times, plaster of paris is so-

called because gypsum was early used near Paris to make plaster

and cement."


Specific reference: Cennino Cennini (in his _Il_ _Libro_

_dell'Arte_, trans. by Daniel V. Thompson, jr., New York;

Dover Publications, Inc., 1960. ISBN 486-20054-X; the original's a

mid-fifteenth century Italian work) uses Plaster of Paris for the

making of molds from life. "Have the man or the woman

stretched out; and have him put these little tubes into the

nostrils of his nose, and have him hold them himself, with his

hand. Have some plaster of Paris ready, made and roasted, fresh

and well sifted. Have some tepid water near you in a basin, and

put some of this plaster briskly on top of this water. Work

swiftly, for it sets fast; and do not get it either too liquid or not

enough so. Take a glass: take some of this preparation, and put it

on, and fill in around the face with it."


Of course, whether it was used for Constance's purpose in

period, I do not know - but at least the stuff itself is period.


(And for those of you wanting to cast from life with PoP, don't. It

gets hot to the touch, ver

y hot; I once measured a batch with a

thermometer, and it topped at 125 degrees Fahrenheit. There are

other ways of life casting. . . )


Alban, whose database of shtuff amazes even him. . .



Date: Tue, 2 Feb 1999 16:27:53 -0700

From: "J. A. Smith" <jasmith at caverns.com>

To: <sca-arts at raven.cc.ukans.edu>

Subject: Re: Plaster on Wood?


From: Rikki Mitman <esmitman at ghg.net>

>Has anyone made a plaster cast of a wooden object to use as a mold? Would

>the plaster stick to the porous wood as badly as I suspect?


>Teleri ferch Pawl


A friend of mine suggests using vaseline, much like you do when you make

casts of people.


Lady Renna of Battersea, Caer Mithin Halle, Outlands



Date: Wed, 3 Feb 1999 02:24:47 -0600

From: Roberta R Comstock <froggestow at juno.com>

To: sca-arts at raven.cc.ukans.edu

Subject: Re: Plaster on Wood?


On Tue, 02 Feb 1999 17:13:53 -0600 Rikki Mitman <esmitman at ghg.net>


>Has anyone made a plaster cast of a wooden object to use as a mold?

>Would the plaster stick to the porous wood as badly as I suspect?


>Teleri ferch Pawl


I haven't tried  it, but would probably want to put somethingon the wood

to keep the plaster from sticking.  Or maybe try making a clay impression

of the wooden object and then a plaster cast from the clay?





Date: Wed, 03 Feb 1999 11:56:49 -0800

From: Lady Eleanor <hekav at gte.net>

To: sca-arts at raven.cc.ukans.edu

Subject: Re: Plaster on Wood?


A lot of art supply stores and craft stores carry mold making

materials.  There is a material...which I can not remember the name of

at the moment..., but I believe there are several brand names on the

market, that is rubbery and flexible when set.  It peels right of the

positive that you are casting, and is specifically made for molds that

have heavy undercuts, and such.  If you wish, I will see if I can find

the name for you.  I think this might cause you a great deal less

aggravation than starting right from plaster, which is brittle, heavy,

and very well might stick to a number of places on your original even

with careful application of vaseline or some other release material.


After you have your rubber-ish mold, then you would cast your plaster

copy in that.


I hope this is of some help.


Eleanor, Lady Leycestershyre



Date: Wed, 03 Feb 1999 12:45:30 -0800

From: Lady Eleanor <hekav at gte.net>

To: sca-arts at raven.cc.ukans.edu

Subject: Re: Plaster on Wood?


I can't find my art supplies catalogs at the moment...(arrrgggh!)...but,

here is one product that I've heard works well...never used it myself.

It's called Instamold...mixes with water and sets in 2 minutes.  Here's

a web page that carries it.  I'll see if I can find more for you.







Date: Wed, 03 Feb 1999 13:13:05 -0800

From: Lady Eleanor <hekav at gte.net>

To: sca-arts at raven.cc.ukans.edu

Subject: Re: Plaster on Wood?


Further source info...


Check this site...



Go to the "Catalog" button (the yellow crayon, at the bottom of the

screen).  Then go to #16 Clays, Casting, Sculpture and, Molding

Supplies.  This will download a .PDF file for you (380K, I think).


Some of the products you want to look at are, Pliatex Mold Rubber,

Moulage (good for face casting), and Silicone RTV Mold Making Rubber.


Also, you might want to look at this link for a huge variety of art

supply houses.  You might find other products or better prices at some

others.  I get Texas' catalogs frequently...but haven't placed an order

yet, so don't know how their customer service may be.  I'd check several

sources before you decide.  :-)




Lady Eleanor



Date: Wed, 3 Feb 1999 15:50:05 -0800 (PST)

From: sion warwick <lostboy_sion at yahoo.com>

To: sca-arts at raven.cc.ukans.edu

Subject: Re: Plaster on Wood?


Another consideration is RTV (room temperature vulcanizing) rubber.

Its usually available at commercial plastic suppliers.  I use GTE's

RTV11, which may be difficult to get (gives off dangerous fumes and is

supposed to only be available to contractors - just tell them you are

a contractor and use a little bravado and they should sell it to you -

works for me).  There are also other versions available. You just

need to make sure they are rated to ~700 degrees or so for pewter.  It

is a two part mixture like epoxy.  Just make sure that it is in a well

ventilated area while curing.  It takes about 24 hours to harden and

about 1 week to completely cure.  I've found that when it is heated

during the casting process it gives off some fumes, so I always have a

fan going.


Here's a quick way to make a mold of an object:  build a frame using

legos thats about twice the size of the object and put it on a board.

Put a layer of clay in the bottom of the frame and sink the object

halfway into the clay.  Build a sprue with clay from one side of the

object to the lego frame.  Mix RTV and fill the lego frame, making

sure the object is covered by at least 1/4 inch of rubber. Let cure

24 hours, then lift lego frame from board and remove clay, leaving

only enough to form the sprue.  Slather it all in vaseline (the RTV

cures to itself really well!), then fill that side with RTV, again

making sure the object is covered by 1/4 inch rubber.  Let cure 24

hours, then remove from frame and let cure 1 week.  When casting with

the rubber mold, use something rigid (like masonite pieces) to

sandwich the mold when you are holding it, or it tends to gap and leak

hot metal.  Also, I recommend pressing a small lego piece bumpy side

down into the clay before pouring the first RTV half to create

registration marks.  Helps hold the mold together without it slipping.


Any other questions, feel free to contact me

Lady Sion



Date: Thu, 04 Feb 1999 15:44:48 -0700

From: Curtis & Mary <ladymari at cybertrails.com>

To: sca-arts at raven.cc.ukans.edu

Subject: Re: Plaster of Paris may be period


plaster was molded and carved and used to decorate and elaborate the frames

for Altarpeices in the church.  I believe also some secular works.


Mairi, ATenveldt



Date: Thu, 4 Feb 1999 22:11:15 -0500

From: "Helen Schultz" <meistern at netusa1.net>

To: <sca-arts at raven.cc.ukans.edu>

Subject: Re: Plaster of Paris may be period


Slaked plaster (a purified form of plaster of paris) was used to make one of

the gilding bases for Gold Leafing in manuscripts.


<proudly spoken like a long-time scribe  :-)>


Katarina Helene



Date: Wed, 17 Feb 1999 03:04:26 EST

From: <EalasaidS at aol.com>

To: sca-arts at raven.cc.ukans.edu

Subject: Re: Plaster on Wood?


On Tue, 02 Feb 1999 17:13:53 -0600 Rikki Mitman <esmitman at ghg.net> writes:

>Has anyone made a plaster cast of a wooden object to use as a mold?

>Would the plaster stick to the porous wood as badly as I suspect?


>Teleri ferch Pawl


I'm running behind and someone may already have mentioned this, but in making

plaster casts of items for use with clay slip, we use "green soap" - it's

liquid soap and it stops the plaster from sticking to your original.  You

should be able to get it at a good ceramic/pottery supply store.


As for someone's comment about being sure you can get the original out - build

yourself a wooden frame as deep as your mold needs to be, coat the sides and

bottom with green soap.  Fill it half full and press your original object

halfway into the plaster.  You will have to support it until the plaster dries

enough that it doesn't sink.  After the plaster is totally hard, coat the

surface with green soap and fill the frame the rest of the way with plaster.

This gives you a mold that will easily split in half without destroying the



You didn't mention what you were going to use the mold for (or I missed it -

I"m speed reading...).  If it's to pour something liquid (like slip), you need

to work a channel into the mold (I use a dowel, or make a clay plug that butts

up against the original).  If your original has pokey out parts, you have to

plan carefully, otherwise you end up with a mold that won't open after

you've poured your casting material into it.




<the end>

Formatting copyright © Mark S. Harris (THLord Stefan li Rous).
All other copyrights are property of the original article and message authors.

Comments to the Editor: stefan at florilegium.org