SkyCeramic@aol.com on tue 26 jan 99
Hi out there,
I've been making molds of bisque pieces and they keep sticking together (the
bisque sticks to the plaster).
I'm using pure lube which I got from my supplier. Is there anything better?
Has anyone tried vaseline, that seems like it might work.
Also, is there a certain length of time you should wait between pouring each
section?
Thanks,
Ruth Jacobson
skyceramic@aol.com
Ross Hartman on wed 27 jan 99
Sky;
Have you thought about making molds of glazed pieces?
That makes it very easy!
Anytime you use a substance like vaseline you leave a residue in the casting
face of the plaster mold itself. In a case like this mold makers (e.g. me :-)
might suggest a sizing of some kind. That might be shellac, or something of
that nature. Possibly a parting compound that would fill the pores in the piece
(assuming non-vitreous bisque).
I've seen others on the list make suggestions of this nature, I think some may
have mentioned the kind of parting compound you would use on polyester molds.
The problem there being that parting compound is not a sizing, i.e. won't
necessarily fill the pores.
If your piece could be fired to be vitreous this would also make it easier.
As a mold maker I would make a mold from a glazed piece (unless the surface
detail or texture was something that _had_ to be transfered as well) and add
detail to intermediate pieces I refer to as plugs. Since a plug is a cast piece
of plaster (usually hydrocal or a mixture of Hydrostorne and pottery #1) it us
very easy to carve, sand, and then polish with mold soap which is actually a
parting compound and a sizing as far as function is concerned.
FWIW...
L8R/Ross
SkyCeramic@aol.com wrote:
> ----------------------------Original message----------------------------
> Hi out there,
> I've been making molds of bisque pieces and they keep sticking together (the
> bisque sticks to the plaster).
> I'm using pure lube which I got from my supplier. Is there anything better?
> Has anyone tried vaseline, that seems like it might work.
> Also, is there a certain length of time you should wait between pouring each
> section?
> Thanks,
> Ruth Jacobson
> skyceramic@aol.com
the Gallaghers on wed 27 jan 99
If you are making plaster molds off of bisque you need a good mold release,
and you need to be sure there are no undercuts to hang the plaster up on.
Vasoline does work quite well with plaster, or you can also try tincture of
green soap, available at any pharmacy.
As soon as the plaster has heated up and set hard you can coat that section
with vasoline and pour the next section.
Cut out "keys" first, by making little indentations where the sections join
together, a spoon or carving tool works well for this.
No need to wait any longer than that, when all sections are set, say 20 min
after the last goes hard, then you can clean up the mold by removing any
sharp edges.
After cleaning the edges, it is advisable to let it rest and not handle the
plaster too much until it cures fully at this point, it can break easily
while there is still moisture in it.
Michelle
In Oregon
Georg =?iso-8859-1?Q?R=F8nning?= on wed 27 jan 99
Hi!
I have made moulds for many years, and in my experience you should avoid making
moulds from bisque. Two reasons, most important is surface in my opinion. I feel
that a mould made this way often has a poor surface , requiring quite a lot of
sanding and polishing to obtain a glossy surface. As long as the mould surface
is smooth and glossy, casts require less trimming. Secondly, the biscue is very
porous, and you should be very lucky to find a slip really sealing pores
properly to avoid sticking onto bisque. I'm still looking ..
I think you will run into trouble very often, wasting time and creating lots of
irritation. Oh, have I tried ...
I find the best way is to glaze the item with a plain glaze, then you normally
get a very smooth surface and you do not have to struggle with plaster and model
sticking together. If the model in question could be turned, I normally turn a
plaster model, use the original UK Crown Soap as slip and have no problems.
Best of luck to you.
Georg
SkyCeramic@aol.com wrote:
> ----------------------------Original message----------------------------
> Hi out there,
> I've been making molds of bisque pieces and they keep sticking together (the
> bisque sticks to the plaster).
> I'm using pure lube which I got from my supplier. Is there anything better?
> Has anyone tried vaseline, that seems like it might work.
> Also, is there a certain length of time you should wait between pouring each
> section?
> Thanks,
> Ruth Jacobson
> skyceramic@aol.com
Georg =?iso-8859-1?Q?R=F8nning?= on wed 27 jan 99
Sorry,
I forgot the question of time between casts. When the cast has crystallized and
lost most of the resulting heat you can normally remove the barriers, soap and
make a new cast. It is very important that the plaster isn't too dry, so there
is no need to wait.
Making a new mould from a dried plaster model will normally give you lots, and
lots of throuble. Even if you soap an resoap, you are still in trouble. Sticking
like .. This is because the dry plaster sucks water from the batch of plaster
you just made, trough the slip. To avoid this, soak the plaster model / mother
mould in water until you see no air bubbles comming out. Then follow your normal
procedure applying slip.
Good luck.
Georg
SkyCeramic@aol.com wrote:
> ----------------------------Original message----------------------------
> Hi out there,
> I've been making molds of bisque pieces and they keep sticking together (the
> bisque sticks to the plaster).
> I'm using pure lube which I got from my supplier. Is there anything better?
> Has anyone tried vaseline, that seems like it might work.
> Also, is there a certain length of time you should wait between pouring each
> section?
> Thanks,
> Ruth Jacobson
> skyceramic@aol.com
Debby Grant on wed 27 jan 99
Dear Ruth,
You would be better off if you made the molds from damp greenware,
rather than bisque. Then you wouldn't even have to use mold soap.
But if there is some reason you must use bisque you could try tincture
of green soap or vaseline, both of which you can buy in a drug store.
Good luck, Debby Grant in NH
orion on wed 27 jan 99
I don't know of many good alternatives to standard mold soaps (like
"greensoap"), but one thing I have come to appreciate IS that it's important
to apply more than one coat to the original (master) piece before making a
plaster cast.
In "Mold Making for Ceramics," the author (Firth) makes quite a point that
you should apply numerous coats of soap -- drying and buffing each coat
until the surface is definitely well sealed.
I've had much better luck with clean, sharp releases since switching to 4-5
(buffed) soap coats -- without changing to a different mold soap. In my own
experience, there seems to be a greater risk of difficult unmolding and
certainly losing surface detail when using vaseline, WD40, edible cooking
sprays, and other oil coatings.
Ellen Baker -- Glacier, WA
(where I've been hustling in the garden to protect early-early sprouting
plants from our morning dusting of snow! Ee-gads!)
Jonathan Kaplan on thu 28 jan 99
I would strongly caution against usuing vasoline as a parting compound for
plaster work for a number of reasons.
1.You may need to remove the pating compound from the plaster at some time,
and vasoline doesn't remove easily as it is not a water based material,
2.It does not enter into the microscopic pores of the plaster, or for that
matter, clay, wood, etc. and will always leave a residue on the surface
that will transfer over into the newly cast piece.
3. It is a chore to apply.
So, spend some money and don't be cheap. Use the Right Stuff for the Right
Job!!!
I would suggest PUP (polyurethane parting compound) from Permaflex Mold CO.
in COlumbus Ohio.
It is a standard for the industry.
Also, Crystal Soap is a good parting compound, as is a make it yourself
type using Fels Naptha Soap and water. Murphys Soap is a good alternative
also.
Do not use WD 40 or other similar distilates. Use water based materials as
they are easy to remove.
Jonathan
Jonathan Kaplan, president
Ceramic Design Group LTd/Production Services
PO Box 775112
Steamboat Springs, CO 80477
(970) 879-9139 voice and fax
http://www.sni.net/ceramicdesign
Brian Crocker on thu 28 jan 99
G'day Ruth,
Hope I'm not Boasting I've made lots'n'lots of molds, It was one of my
teaching subjects for quite a few years and then in Industry.
I tried many release agents Vacelene included, it gives great release but
the Mould is'nt worth a Penny after , all the pores of the plaster are
clogged up and the mould wont work, only good for a door stop.
The best thing I have found is the Old simple Bar soap like Grandma used to
use, no perfume, no colour and a pH of 7 or a little alcaline.
Just get the Bar soap grate it up into a bowl add a little water and let it
stand for a while come back later and give it a stir, it takes time but what
you eventualy want is a gell not too thick just brushable.
Dampen the Pot with a sponge, make sure it is not too wet, brush on the gell
with a 'soft' brush, leave it to dry, only a little, and rub off any excess
with your hand, fingers can 'see' lumps your eyes will never pick up. A
Blind friend once told me that " You sighted people are often hindered by
sight " .
Now leave the soap film to dry then Burnish it with a cloth similar to an
"old" child's nappy [daiper],[no fluff]. Cover and allow to dry a little
more. Gently
brush on more soap and wipe off the excess and so on. Do this three times,
ensure there is no build-up in corners or concaves. Now leave to thoroughly
dry then burnish untill you have a shine. The Pot or Model is ready to make
a plaster mould from. Cast the mould and when thoroughly dry use it for slip
casting press moulding or what ever, the first one or two parts wont be so
good but after that you have a workable mould..
I have the above info and more, in an attachment, so if you are interested
let me know and I will send it in an e.mail.
Kind regards, Brian C.,
At 07:51 AM 26/01/99 EST, you wrote:
>----------------------------Original message----------------------------
>Hi out there,
>I've been making molds of bisque pieces and they keep sticking together (the
>bisque sticks to the plaster).
>I'm using pure lube which I got from my supplier. Is there anything better?
>Has anyone tried vaseline, that seems like it might work.
>Also, is there a certain length of time you should wait between pouring each
>section?
>Thanks,
>Ruth Jacobson
>skyceramic@aol.com
>
>
Brian Crocker
4 Erica Street,
Tea Tree Gully 5091,
South Australia,
Australia.
{e.mail} crocker@dove.com.au
"Never loose sight of the bigger picture,"
"Never loose sight of what you set out to achieve."
NAB.
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