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Balloons As Sphere Molds


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#1 Grendus

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Posted 16 December 2013 - 03:54 PM

Let me preface this by saying that I'm not very knowledgeable about ceramics. My understanding of ceramics stops at about the point where I recognize that clay is different from potting soil. My sister, however, is a ceramics major and is extremely passionate about it. One of the methods she uses for making spheres is to cover the outside of a round object with the clay. Currently, she does this with styrofoam balls, but this is a laborious task that involves cutting the balls down to the right size and shape and can be dangerous if the ball comes off incorrectly and winds up warping the structure. She mentioned that using a balloon for this would be ideal as they're cheap and you can just pop them and pull the latex out when you're done, but balloons tend to roll around so you either have to tape them down, which is difficult and fails half the time, or keep them in a bowl, which puts too much strain on the balloon and causes it to burst.

 

With Christmas coming up, I want to get something that would simplify some of the difficulties she's been having with hand building round shapes, but I had a few questions:

1. I did a little research and found that some people fill balloons with sand or cat litter to give them more rigidity, then drain the particles out to pull the balloon out. Is there any way to inflate the balloon with sand or other cheap particulate matter, or do you have to find a slack mold that's already the size you want to use (some mentioned using tube socks, for example)?

2. It's possible that a higher grade of balloon could hold up under the weight of the clay better. Has anyone tried doing this? Did it work?

3. Does anyone have any other suggestions for an easy and cheap spherical mold?



#2 Denice

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Posted 16 December 2013 - 05:20 PM

I remember one student when I was in school making two part plaster molds from styrofoam premade balls you buy from a hobby store.  When the plaster was set up he would melt the styrofoam away I believe with acetone.  I don't think he poured slip in it, I think he pressed clay in each half and then joined them together.  May be someone will have a better answer.   Denice



#3 Kohaku

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Posted 16 December 2013 - 05:49 PM

Let me preface this by saying that I'm not very knowledgeable about ceramics. My understanding of ceramics stops at about the point where I recognize that clay is different from potting soil. My sister, however, is a ceramics major and is extremely passionate about it. One of the methods she uses for making spheres is to cover the outside of a round object with the clay. Currently, she does this with styrofoam balls, but this is a laborious task that involves cutting the balls down to the right size and shape and can be dangerous if the ball comes off incorrectly and winds up warping the structure. She mentioned that using a balloon for this would be ideal as they're cheap and you can just pop them and pull the latex out when you're done, but balloons tend to roll around so you either have to tape them down, which is difficult and fails half the time, or keep them in a bowl, which puts too much strain on the balloon and causes it to burst.

 

I haven't tried to do this... but I'm keen to make some sphere molds, and thus really keen to hear how things work out for you.

 

Unfortunately, I've had multiple people tell me that balloons will warp. The poured plaster exerts pressure, and the balloon's form will warp both symmetrically and asymmetrically (due to unevenness in the latex). Since the goal in creating a sphere mold is to have the most symmetric form possible, this would be a deal-breaker for me.

 

I've been told that you're far better off using rigid spheres (like bowling or bocci balls) or half spheres. I have yet to accumulate any of these and make the experiment, unfortunately.

 

<Edit>

 

D'oh... just re-read the OP, and realized that you're talking about using balloons as a base for forming clay. Totally different scenario... ignore everything I just said. :wacko:


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#4 Chris Campbell

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Posted 16 December 2013 - 06:06 PM

I use balloons all the time ... In fact my newest work as seen in the aesthetics section of this forum is all done around balloons.
Use the heavier duty ones ... You can find bags of these in drug stores or party supply stores. No need to pay big bucks but do not get the thin ones.
The trick is to buy different sizes so you can under inflate them ... there should be a soft neck on them. That way when the clay starts to dry it will simply keep inflating ... If you blow it up all the way the stress has nowhere to go. After a day or two of the clay drying and she feels safe that it can hold its shape, simply prick a very small hole in the soft neck part and the balloon will slowly deflate and release from the sides. Pick out the used balloon and all is well.
You can paddle against it and shape your clay without the balloon exploding. She can lay it in a bowl if she does not want a flat bottom.
They can also be filled with sand then sliced open and emptied ... but I have never bothered with this.
BONUS for you ...you get off cheap this Christmas by buying sis a few bags of balloons! : - )

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#5 Babs

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Posted 16 December 2013 - 07:04 PM

I have made sphere molds with vaselined balls of various sizes, up to basketball size. 2 piece plaster then  keyed together. Can use as two hemispherical press molds.



#6 David F.

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Posted 16 December 2013 - 09:24 PM

Years ago I did art therapy with kids and one of our projects was to create jack o lanterns with slabs formed around balloons. It was a fun easy project.....we weren't concerned with getting "perfect spheres".


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#7 Marcia Selsor

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Posted 16 December 2013 - 09:31 PM

You can pour plaster on the balloon. Actually condoms work better because they seem to be a heavier latex.
I use various sized balls for spherical molds. I recently made 8" and14" molds.

#8 Chris Campbell

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Posted 16 December 2013 - 10:13 PM

Do you need to put a barrier of some kind ( oil or soap ) on the balloon before you pour the plaster Marcia?


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#9 Marcia Selsor

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Posted 23 December 2013 - 05:05 PM

No. Just fill with plaster to the desired size and tie a knot.
Chris, if you plan to cast a form from the positive form, then yes, use should use a mold release of some type, WD 40, oil, vaseline, etc.
I have cast many different materials for forms and sprigs. Brushing a light coat of cooking oil of. Mineral oil
On details wooden objects worked without any problems.

Marcia

#10 JustPeachy

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Posted 25 December 2013 - 08:44 AM

You can pour plaster on the balloon. Actually condoms work better because they seem to be a heavier latex.
I use various sized balls for spherical molds. I recently made 8" and14" molds.

 

laughing-dog-smiley-emoticon.gif

 

I haven't bought condoms in like forever!

 

"Why, yes Mr Pharmacist, I want to make molds with them.... Really!"



#11 Marcia Selsor

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Posted 25 December 2013 - 12:42 PM

You can buy large quants at Costco!
Maybe it is more discreet or maybe excessive!
Marci

#12 JustPeachy

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Posted 25 December 2013 - 06:23 PM

You can buy large quants at Costco!
Maybe it is more discreet or maybe excessive!
Marci

Perhaps over optimism? rolling.gif



#13 Babs

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Posted 25 December 2013 - 08:22 PM

YOu Guys imbibing on a little xmas cheer??

Go centre some clay!!

Marcia, now you have your ballooon mold, plaster , how do you use it??That is clay on inside, outside, I have a little wine in me and can't get around getting the clay form off or out of the balloon mold!

Don't laugh ser=ious request for hte brain blocked.



#14 Evelyne Schoenmann

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Posted 26 December 2013 - 06:27 AM

 

You can pour plaster on the balloon. Actually condoms work better because they seem to be a heavier latex.
I use various sized balls for spherical molds. I recently made 8" and14" molds.

 

laughing-dog-smiley-emoticon.gif

 

I haven't bought condoms in like forever!

 

"Why, yes Mr Pharmacist, I want to make molds with them.... Really!"

 

 

This is the funny part of our (clay) passion, JustPeachy! Marcia is right though, condoms are stronger and work better. They are not really big though....

 

Happy Holidays my friends, with or without wine inside...

 

Evelyne


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#15 Mart

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Posted 26 December 2013 - 06:57 AM

No. Just fill with plaster to the desired size and tie a knot.
Chris, if you plan to cast a form from the positive form, then yes, use should use a mold release of some type, WD 40, oil, vaseline, etc.

Marcia


Are you sure? I have always avoided oils because it will transfer to the final mould surface. You do not want any oil on the surface of your final mould if you are going to slip cast because oil will screw up water absorption - ruins your mould.

Cover the master mould (plaster) with very thin layer of shellac and then few really thin even layers of soap (dish washing soap is probably fine). After it's dry, use soft toiletpaper to wipe off the excess and you are ready to pour your plaster over your master mould.



#16 bciskepottery

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Posted 26 December 2013 - 08:48 AM

Maybe CAD could do a video on using condoms for balloon molds . . . can almost guarantee it would go viral.  Hey, CAD . . . push the envelope, break new ground in 2014!



#17 Marcia Selsor

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Posted 26 December 2013 - 11:30 AM

mart, you are right for slip casting. I don't use most molds that way. I use them as press molds. Vaseline was the release of choice when I first started making molds. I really likeWD 40 although it stinks. Pine oil soap was also taught to me as well.I never noticed any problems from using the above for a mold release

Marcia

#18 Marcia Selsor

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Posted 26 December 2013 - 11:36 AM

For
Large spherical molds I use balls as the positive mold. I cut heavy cardboard to fit half way around the ball, use a clay wall about 1.5 " around the edge! and pour the upper half? Then remove the cardboard, make keys use a mold release and pour the second half..

Marcia

#19 Mart

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Posted 26 December 2013 - 04:17 PM

WD 40 although it stinks.

 

What do you mean it stinks? I use it as an deodorant and aftershave!  WD 40 has saved me marriage 6 times and helped me sell 9 used cars.



#20 Babs

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Posted 27 December 2013 - 04:31 AM

 

WD 40 although it stinks.

 

What do you mean it stinks? I use it as an deodorant and aftershave!  WD 40 has saved me marriage 6 times and helped me sell 9 used cars.

 

Beware MArt, my partner says that it attracts dust.. you a potter? better try graphite!






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