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1967 Tiki mug mold |
Rain
Tiki Socialite
Joined: May 27, 2002
Posts: 431
From: Providence, RI
|  Posted: 2003-05-30 01:40 am Permalink
i haven't tried anything yet - no molds to use.
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MonkeyPaw
Tiki Centralite
Joined: May 26, 2003
Posts: 59
From: Reno
| Posted: 2003-05-30 12:48 pm Permalink
If you look around on the internet you can sometimes find places that carry discontinued molds. Start with Duncan.. Im sure they can refer you to a company that sells discontinued molds. As far as making a mold.. HMM .. I have not researched that.. But I'll do a little fishing around and see if I can come up with some info...
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Saint-Thomas
Tiki Centralite
Joined: Sep 26, 2002
Posts: 39
From: Knoxhell
| Posted: 2003-06-02 06:36 am Permalink
Molds are easy to make. Just be certain you use the right stuff. Plasters come in many flavors, and you want one with a high compression like Hydrocal.
If you want to keep that 1967 mold, don't use it. Every time the mold gets wet it will be degraded. A typical mold lasts about 100 castings or less. Instead, make a casting from that mold, then make a new mold.
Also, plaster molds need to be kinda wet to work properly. If my mold is completely dry, I will dust it with Talc (magnesium), cast once, then trow away that casting. The mold should be good to go at this point. Just don't cast more than a few times (3 or 4) in a day or it will be saturated and easily damaged.
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suffering bastard
Tiki Centralite
Joined: Feb 08, 2003
Posts: 69
From: Silver Spring, MD
| Posted: 2003-06-02 09:47 am Permalink
Does anyone know if you can make molds for ceramics from silicon instead of plaster? I don't know the first thing about ceramics, but I know silicon (although expensive) is durable, flexible (good for undercuts), and captures detail extremely well. Maybe a silicon mold with a plaster mother mold for support? The only thing is, I'm not sure if the plaster mold interacts with the slip---does it absorb some of the moisture from the slip as part of the drying process? If so, I don't think silicon would do that. If any experienced ceramic people know the answer, I'd really appreciate it.
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MonkeyPaw
Tiki Centralite
Joined: May 26, 2003
Posts: 59
From: Reno
| Posted: 2003-06-02 10:05 am Permalink
Hi ST. Tom -
Thanks for the info. I had no idea that molds did not last very long. I think I will take heed to your advise and preserve the mold. I did notice that when I did use the mold that after one pour the plaster felt pretty damp. It was almost like I felt like you'd have to wait for the plaster to dry up a bit before you pour the next item. Do you know of any company's that reproduce molds? I wouldn't trust myself to do it....
[ This Message was edited by: monkeypaw on 2003-06-02 10:12 ]
[ This Message was edited by: monkeypaw on 2003-06-02 10:13 ]
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MonkeyPaw
Tiki Centralite
Joined: May 26, 2003
Posts: 59
From: Reno
| Posted: 2003-06-02 10:10 am Permalink
Suffering Bastard - I believe the Plaster mold works because it is h2o soluable.. the slip you pour into the mold is basically liquid clay. The plaster absorbs the excess h2o which helps the clay firm up. I tried a plastic mold one time with a cement type mix and it did not work as well as I thought.. there was no where for the h2o to go. Something other than plaster that would be h2o soluable seems the way to go...but what? Hmmmm
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suffering bastard
Tiki Centralite
Joined: Feb 08, 2003
Posts: 69
From: Silver Spring, MD
| Posted: 2003-06-02 12:29 pm Permalink
I thought that might be the case----bummer.
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Saint-Thomas
Tiki Centralite
Joined: Sep 26, 2002
Posts: 39
From: Knoxhell
| Posted: 2003-06-02 6:26 pm Permalink
MonkeyPaw---
It's supposssed to be damp. that way the clay doesn't stick when you remove it. A totally dry mold will cause problems with absorption rate. However, it should be allowed to dry somewhat between castings.
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Silicon doesn't sound like a good idea to me. (I assume you mean the gooey kind in the tube.) There are several latex products out there which will take a higher detail. Generally they are used for creating other plaster molds, or, for non-hollow pieces with undercuts. Yes, a mother mold of plaster is used for support. For slip casting, you pretty much need something to absorb water, ie. plaster. You can make an unlimited number of pieces to accommodate the undercuts as long as each part is keyholed. Complicated shapes I've seen used as many as six or seven parts for the mold.
There are a couple of consulting services:
www.ceramicdesigngroup.net and Contact Reach Molds, 20 Camp Rd. 41, Ogdensburg, NY 13669, (315)393-6065. I don't know what they charge, but your local pottery studio or ceramics supply house might offer these services also.
I have considered jobbing out my mold making to someone, but it really is very inexpensive to do it yourself. If anyone wants me to recommend some books on how to do it, I'll try to dig up a title or two. I just don't have that info right now...
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Saint-Thomas
Tiki Centralite
Joined: Sep 26, 2002
Posts: 39
From: Knoxhell
| Posted: 2003-06-02 6:33 pm Permalink
Oh, I forgot this info--sorry for the double post!
Plaster is not water soluble. It is a hydrate of calcium. That water does not go away unless you break the molecular bond by heating to a certain temperature. In theory, you could "revitalize" old plaster by heating it in an oven. Same goes for a mold. If you were to heat it up to, oh, say about 500 degrees, it would fall apart as the H2O is driven off.
The reason plaster molds absorb water is due to the porous nature of the molecular structure. The water is actually going into the spaces in between the plaster molecules.
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MonkeyPaw
Tiki Centralite
Joined: May 26, 2003
Posts: 59
From: Reno
| Posted: 2003-06-03 12:39 am Permalink
St. Tom - Thanks for the science lesson. No joke... I had no idea how complicated all this could be. You are truly the Alton Brown of Ceramics. Do you make your own molds? I'd like your recommendation on "How to" books. Are you self taught?
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Saint-Thomas
Tiki Centralite
Joined: Sep 26, 2002
Posts: 39
From: Knoxhell
| Posted: 2003-06-03 8:54 pm Permalink
HEy Monkey,
Yes I am self taught. I actually read a chapter in a book about it once while drinking coffee at Borders, so I had kind of a head start. That book is called "Big Book of Ceramics" by Joaquim Chavarria.
HE also writes other books including a couple dealing with moldmaking and slip casting. One book I've heard about is called "Moldmaking for Ceramics" by Donald Firth. I've not read it, however.
You could also get some help online at http://www.potters.org/category180.htm
I have learned most of this stuff by reading.
I wish I could help out more with book titles, but I simply haven't read any of the books specifically addressing moldmaking. I thought I had more titles than that available, but I can't find that list.
Potters.org is a very valuable resource and should help you (I was a potter before I discovered slip casting, so I had no problem catching on)
Good luck and feel free to email with questions. (this offer is for anyone on board)
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MonkeyPaw
Tiki Centralite
Joined: May 26, 2003
Posts: 59
From: Reno
| Posted: 2003-06-03 10:52 pm Permalink
Thanks St.Tom - Have you tried anything out? We have a ceramics Co. here in Reno that is going out of business..so I went in and bought up a bunch of molds. Unfortunatley the only ceramics places we have left are those ones that sell plates and mugs that you paint and they fire. Nothing interesting.
I'll check out your book recommendations..thanks again!
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Tiki King
Tiki Socialite
Joined: Jun 13, 2002
Posts: 534
From: Lush tropical Santa Cruz, CA.
| Posted: 2003-06-06 1:32 pm Permalink
One thing about dwell time ( how long you let the slip "dwell" in the mold. It depends on a few factors. air tempeture, humididty, and how long you let the mold "rest" between castings. On a hot day, with a dry mold, you might be looking at 15 min. Cold and damp, 25. also a factor is the slip viscosity. a thinner slip will take a longer dwell time, thicker slip less time.
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