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Author Topic: Mold Making  (Read 5052 times)

bsilverman

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Mold Making
« on: August 19, 2011, 05:08:30 PM »
I have a sculpture and now would like to make a mold from it. Once mold is made i would pour ArtPlaster into the mold to make duplicates of it, ... i hope!

The first problem i have is that a two pc mold wont work because of all the extremities ie. the 4 legs. I'm guessing i need a four pc mold. I have some idea how to make it but wonder if anyone has a tried and true method or know of any tutorial that demonstrate  how to do it.

I can find demos for two pc molds of symmetrical items only.

Thanks for any help.

brian

rubyrube

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Re: Mold Making
« Reply #1 on: August 19, 2011, 05:43:58 PM »
Have a look at making molds and casts for pottery clay.  I did once do this at adult ed (too long ago to remember exactly how), but know you have to make certain undercuts in the mould. What you need to be able to do is take out the cast item without any parts going back on themselves, otherwise air will get trapped and the plaster wont get into all the right places, also the mold or cast might break when taking it off.

Hope this helps, you might find something on you tube which will explain it better, Carol
Carol

bsilverman

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Re: Mold Making
« Reply #2 on: August 20, 2011, 01:31:23 AM »
What you need to be able to do is take out the cast item without any parts going back on themselves, otherwise air will get trapped and the plaster wont get into all the right places, also the mold or cast might break when taking it off.



Yes of course that is the problem. Well my first attempt resulted in the mold breaking as i was de-molding it. I now am wondering if i should use polymer clay to make the mold or at least the more detailed inner parts.

try try and try again.

MelMcG

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Re: Mold Making
« Reply #3 on: August 20, 2011, 12:45:21 PM »
Sorry I can't help, but I'm interested to see how you get on with it.  :) Mel

rubyrube

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Re: Mold Making
« Reply #4 on: August 20, 2011, 04:28:41 PM »
You could try latex to make the mold. There are some videos on you tube about using this that might help.

Carol
Carol

bsilverman

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Re: Mold Making
« Reply #5 on: August 20, 2011, 05:26:31 PM »
Thx Carol. I probably should just use latex as it would be flexible. I am trying not to buy anything tho. Am on my second attempt with ArtPlaster and it is a challenge getting a separator line. Making lots of mistakes but plunging ahead anyway.

rubyrube

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Re: Mold Making
« Reply #6 on: August 20, 2011, 07:38:07 PM »
Fingers crossed it works out or at least you learn from it.

Carol
Carol

bsilverman

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Re: Mold Making
« Reply #7 on: August 21, 2011, 06:46:16 PM »
Tried once again to make a mold using ArtPlaster by laying my pc on its side building a divide line with plasticine, then pouring the plaster. First pour was ok. Then the second divide line was hard to figure out but i layed out some more divide lines and poured on top of the first. Part of that broke on demolding, but not serious. Still i can see i'm going nowhere with this method. There is just no way to do it with this method that i can figure out.

Searching the net for answers i think i found the right way to make a dividing line. Unfortunately i also think a flexible mold material is also a must.

http://www.figurativesculptors.com/index.php

---Construction techniques and processes
Materials, products, processes, suggestions and tips involving how sculpture is made.

---How to Make A Bronze by the Lost Wax Process by mantrid

It doesn't look easy and i have to question if its worth it or not. Still pondering that...



ejralph

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Re: Mold Making
« Reply #8 on: August 21, 2011, 07:07:52 PM »
Do you have a photo of the item you are trying to make a mould of?

Emma
Emma from Sunny Sussex, UK
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bsilverman

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Re: Mold Making
« Reply #9 on: August 21, 2011, 07:51:42 PM »
yes, its the giraffes

ejralph

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Re: Mold Making
« Reply #10 on: August 21, 2011, 09:51:17 PM »
I see!

Yes - a solid mould for that would entail several parts wouldnt it. I used to have a really good book on making moulds, for ceramic pottery rather than polyclay, but the principles are the same of course.

But if you will be pouring plaster into the mould, surely flexible latex or similar is the best way to go anyway - and you won't need to worry about the undercuts. I think it will be one of those cases where a few quid on materials will save you a lot of work, failed experiments and head scratchings maybe?

Do let us know how it goes though won't you.

Emma
Emma from Sunny Sussex, UK
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bsilverman

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Re: Mold Making
« Reply #11 on: August 22, 2011, 05:11:39 AM »
Well i have abandoned the plaster mold, but before discarding it, I did a pour on the finished part, which is two left side legs. I put a wire in one and left the other to see if it would make a difference.

When i removed the top half of the mold the unreinforced leg broke, as it was a bit too difficult to pry apart. The reinforced leg stayed in tack even tho there was a huge air bubble almost severing the leg.

Carol you are right i did learn a good deal from this, and from relentlessly searching for info.

Emma you are right that investing in some latex would be well worth it, and i have done that. I think its best to finish the sculptures before attempting another mold tho, now that i have satisfied my curiosity.

ejralph

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Re: Mold Making
« Reply #12 on: August 22, 2011, 01:15:09 PM »
I've always learned about 20 times as much from the experiments that went wrong as I ever did from those that went right.

Nothing is ever truly a waste of time, even if the results aren't what you hoped for.

Emma


Emma from Sunny Sussex, UK
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babysloth

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Re: Mold Making
« Reply #13 on: April 19, 2012, 07:17:55 AM »
I have succesfully made molds with two component silicone rubber. You can cast it in one piece and then cut the original sculpture out with a craft knife (You can make multiple cuts too - silicone is very flexible). The mold is very durable too. I've also used two component liquid plastics/resins to make castings in those molds. Very easy and fun, but costs more than plaster.
Jutta