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Making Copies Of The Mother Plaster Mold


natanata

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Hello dear colleagues,

 

I have a question here about slipcasting technique and mold making process.

Some of my work I make with porcelain slip and plaster molds, I have made several different molds to cast porcelain cups. But as I have only one mold of each shape, casting process is slow, I can cast only up to two cups a day from each cup.

Do someone of you have an idea, how to make a copy of already existing mold? To make several mold for the same shape? I will be so happy to hear all the suggestions!

Thank you!

 

Nata

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As far as I know, the only way to make more moulds is to pour a new side/top/bottom, one at a time, for each of the moulds you have.

 

So, if you have a three-piece cup mould, you apply soapy release on the plaster, then fill the mould with plaster.  You then remove one piece of the mould, leaving the other two pieces and the plaster cup in place.  Put walls around with the missing piece uppermost.  Apply soapy release and pour plaster.

 

You now have one extra piece of the original three-piece mould.  Repeat with each of the other two sections, until you have two complete moulds and one plaster cup.  Now you can pour another plaster cup and repeat using both the moulds to create two more moulds.

 

It is time-consuming..........

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You need a master mold which all copies of working molds are made-you should read up on this process-Since you already have a working mold making a master from it would involve pouring a durable plaster like hydrocal into that mold. This most likely will kill your working mold but then you can make a rubber mold from that and working molds from this mold. Working from a postitive to a negative in rubber to make the rubber mold which all working molds come from.

Its a pain and will cost you in materials .You need a good mold making book.You could also pay a master mold maker to do this for you if you are planning on a production run of these cups.

Mark

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A book I highly recommend as a 2nd book on mould making is:
Chaney [and Skee], Plaster Mold and Model Making.

... if you're quick there is a 2nd-hand copy going for ~17$
https://www.amazon.com/gp/offer-listing/0671764675/ref=sr_1_1_olp?s=books&ie=UTF8&qid=1474205040&sr=1-1&keywords=chaney+Plaster+Mold+and+Model+Making

Besides giving a lot of useful advice on designing/making multi-part moulds, pp62-81 is a worked example of making a 2-part+spare

mould of a frog, then making the associated plaster block&case-moulds. It also has a very interesting section on plaster-build-up as

an alternative to the usual clay-bed method of making multi-part moulds.

 

Making plaster multi-part block&case moulds looks to be a lot of work!

 

Another approach I've seen describes uses a flexible casting rubber to make one-piece block-moulds for each part of your master-mould.

Relying in the flexibility of the rubber to release your master-mould parts (after casting the rubber), and your copy-mould parts (after casing

them in plaster). Sounds more expensive, but a lot easier. Not, I hasten to add, that I've any experience with casting rubber. Finding the

right product may be a problem, and I'm unsure what effect it would have on your master-mould parts.

... this sort of thing:

 

 

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I had a slip business on the side once and had a master mold maker make our master  mold then block and case molds of rubber so we could cast the working molds. I have been thru this process to know its best done by a pro if its going to be a lot of working molds made. We made many hundreds of working molds from the rubber case molds-our form was a 3 piece mold.The rubber  mold making supplies can only be shipped in summer or non freezing conditions.

Mark

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Oh, no one has told you yet.

 

Well, ya see... when a mommy mold and a daddy mold ~really~ like each other... ;):lol:

 

 

We've always farmed out mold making and it isn't cheap by any measure. Who made the ones you have now?  Chances are you have something no longer made by someone like we do. We heave a great mold she bought at a garage sale long ago. We would love to have another one made but it costs too much. Short of having more made perhaps it would be best to always be pouring and build up stock.

 

I've often wondered how much putting a mold in the frige would speed up mold drying but I like being married too much. :D

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Hello dear colleagues,

 

I have a question here about slipcasting technique and mold making process.

Some of my work I make with porcelain slip and plaster molds, I have made several different molds to cast porcelain cups. But as I have only one mold of each shape, casting process is slow, I can cast only up to two cups a day from each cup.

Do someone of you have an idea, how to make a copy of already existing mold? To make several mold for the same shape? I will be so happy to hear all the suggestions!

Thank you!

 

Nata

 

Hi Nata!

 

I am also into mold making and slip casting, although I am still a beginner in things related to traditional ceramics.

 

My approach is quite mechanised as my background is in 3D.

 

Depending on your budget, you could take 2 optional approaches.

 

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1. Old-school method (For simple designs) is I would just slice up the primary mold between the undercut areas and than cast each piece again individually.

 

You are going to be duplicating so might as well sacrifice the primary mold as you only have one piece and eventually you will have to make more so better to take the risk earlier than wait with anxiety lol...

 

A jewel saw with wired, tapered double sided saws (Wire saw) works very nicely. They are quite costly the saws so probably better to buy them online (Ebay). If you are really interested, let me know and I can give you info on the exact type of saw I use and their blades. I need to search my garage...

 

Just remember to soap up the original mold very well before casting. I use murphy's oil soap.

 

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2. If you know a small local 3D company, you can ask them to do a 3D digital scan of your mold and than they (Or you) can send the digital scanned file to a CNC cutter to cut up the molds for you directly. I do everything in-house by myself in my studio - minus the 3D scanner as I am still saving up money for it. Without a 3D scanner, you would need to know 3D software and actually do the modelling yourself - which is more time consuming.

 

The great thing about this aspect is you have absolute control in mold production. All you need is maybe supply the private CNC miller (I am sure someone in your area owns a CNC machine somewhere) a block of semi-cured plaster block for milling. The most expensive part might be the 3D scanning service and prices really fluctuate depending on where you live.

 

Just remember to go for small scale studios as they will be more reasonably priced compared to large production houses who charge an arm and a leg and you can easily rack up a bill of more than 300.00 - 500.00 USD for replications. If you can find someone to replicate 2-3 molds for you for 150.00 - 200.00 a piece - it is a steal although most budget and traditional ceramicists might be shaking their heads.

 

The second option is recommended only if you want to replicated very complex molds - like figurines or creatures with lots of different parts and intricate details.

 

Also, if you want to go the second option, make sure to mention you are making molds, or else the digital production house might slice and splice the file layers in a way that will leave you with undesired undercuts and those undercuts will get milled during the CNC process.

 

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I hope this was helpful and feel free to ask any questions you may have to inquire.

 

- Steven

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