3 years ago#1
Guest
Guest

So I sculpted this cat in clay...I actually placed the clay over a primitive fiberglass model...
When the clay dried it cracked in several locations....Does it always do this?..How would I prevent this?

So OK...I mend the cracks with more clay....and I was thinking I would fire it to get my ceramic figure...But now I am thinking it will crack more...

So now I am thinking to make a mold ...what should I use?
And then do a traditional ceramic figure from the mold...

Thanks.

Answer
3 years ago#2
mickpearson
Master
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HI. was the clay an air drying clay?or a firing clay. did you let it dry by itself. and did you use the fibreglass as an armature model of what?

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3 years ago#3
lrfowler
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Hello,
thanks for replying...
it was pottery clay...I let it air dry....I am told it needs to be fired at a high temperature....
So initially I thought I would do the cat in fiberglass...but that proved pretty rough and hard to use...So I used the fiberglass cat as a model and I added clay on top of it...
When the clay dried it cracked in several locations....Does it always do this?..How would I prevent this?

So OK...I mend the cracks with more clay....and I was thinking I would fire it to get my ceramic figure...But now I am thinking it will crack more...

So now I am thinking to make a mold ...what should I use?
And then do a traditional ceramic figure from the mold...

Reply
3 years ago#4
red46
Gold Member
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UM....it WILL crack. Natural clays, called earthenware or stoneware are water and clay based and shrink about 5% during drying and another 5% during the firing. Not only that, fiberglass doesn't go in a kiln.

You have to let clay dry slowly and at it's own accord, with nothing under it preventing it from shrinking.

You can sculpt or make a mold and pour the object, either way works great. I think you need to pick up a book on how to work with clay because it's important to keep edges covered up with foil or something like saran, to let the rest of the body catch up with the drying process. Since clay dries from outside in, those edges will dry too quickly, binding the rest of the object and not allowing it to shrink. So the idea is to slow down those areas that will dry faster than the rest.

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3 years ago#5
mickpearson
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HI. thank you for the feed back. there are a hundred ways to help you out. without trying to be to technical. and i like to explain in simple terms. as most people are first timers that ask for help.you can make models in the clay you where using. its just the fibreglass armature that mest you up. you will have to buy the correct ceramic plasters to make moulds of your models and then make some goo out of slip and clay then it would be fired you can find a course near you. and learn this but you could do other methods that are far more simpler like making moulds of your clay models for casting in any other medium.be it concrete.plaster.or.resin. but im under the impression you want to make ceramics.

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3 years ago#6
Larry
Guest

OK...so which would be the easiest to make a copy of the cat?...resin?
which products do I get?

thanks!

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3 years ago#7
mickpearson
Master
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HI. sorry about the time laps i am going to give you more than one method. and they are all easy. method no.1 is you model your cat in its pose with your clay and your clay will only be damp so you need latex to make the mould you would use a paint brush to dip in your latex and dribble the first coat of latex on to your cat model and gently pat the first coat on to burst any air bubbles
model your cat on a flat piece of plywood and paint a flange around the bottom of your cat so you will know when your mould is thick enough to peel of when ready you will need to paint several coats of latex on to your model letting each coat semi drie until you are happy your mould is thick enough you can test this by lifting a little piece of your flange up and see if it feels thick enough if you are happy dust it with talcum powder leave it on your model don.t worry about you clay cracking it wont . you are now ready to make a support jacket for your latex mould this can be made in plaster or fibreglass that part is you choice the plaster method first. depending on the complexity of your design would be to section some clay on top of your latex mould in two or three halves you decide how many it will need example say you only need two halves you would put clay around your latex rounding of any under cuts wich are deep areas that the support jacket might get stuck to so you will have to chamfer them of then mix your plaster and put it on one halve of your latex using plaster bandage and your plaster mix when this coat is dry you are ready to do the other halve remove your clay and rub some beef drippin on the plaster halve seem only to stop the plaster from sticking to itself you can use vaseline but be careful not to get it on your latex moulds it damages latex. i will tell you how the other method works on the next link.

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3 years ago#8
mickpearson
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the other method would be to use a fibreglass jacket on your latex mould if your cat was really big enough to need one i make garden ornaments and what i do is i use thin cardboard and line it up against my latex that has a model inside it and use a pen to draw the profile around my latex mould and then cut it out with scissors then use masking tape to stick it around my mould in however many halves i need it is much more tidy than using clay as the clay gives you a more ugly mould. i then use acrylic varnish on my cardboard when dry spray release agent my cardboard and ime ready to lay my fibreglass i don.t use gelcoat or release agent on the latex because it does not need it and the next method would be a silicon mould dragon skin is like latex but quicker than latex you just paint it on in the same way other silicon moulds you would paint it on till your mould is thick enough then use a little of silicon thickened with thixotropic paste and put it around the sections you are going to cut apart when your mould is ready you will now put clay one section at a time on your mould halves and make impressions on your clay with the back of a spoon or a marble to form keys for the other halve of your mould not forggeting to spray each halve with release agent first so that your halves don.t stick to each other when you have made your jacket and are ready to cut your mould open it is up to you what medium you will use to cast with be it plaster or resin if you use plaster then with the right release agent you can make a plaster mould of the plaster casting and then you can make a ceramic model but you will need the right plaster . i hope i have not bored you with to much info yet i could go on and on but i hope i have helped you out

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3 years ago#9
red46
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Since you are already messing with potters clay, I'd suggest you continue in the clay mode. With pottery clay, you will need a plaster mold.

I realize you probably have a whole slew of undercuts and that takes some practice, understanding how to make a plaster mold so you have a choice; learn how to make plaster molds or go for a flexible rubber that will stretch over your model.

Here's a quick brief to help you understand your different avenues. With wet clay, your best to go the clay avenue which involves molds of plaster, which you then can pour slip into or press clay into
OR
stick to the rubber compounds and use the rubber mold to pour resin or plaster or concrete or whatever...anything except clay or clay slip. How's that for narrowing it down?

So the first thing is to decide if you want a finished product made of clay or do you want a finished product of just about anything else. Answer that, and we can help you narrow it down.

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3 years ago#10
Larry
Guest

I'm thinking resin is the solution now...
I don't understand the part about wet clay....because my clay sculptured cat is now dry and no longer wet.

Initially I was thinking make a plaster mold of my clay sculpted cat with fiberglass in the middle..

do you have to make 2 halves of a box or something to hold the wet plaster and then dip the sculpted kitty in somehow?...and close the box?

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3 years ago#11
red46
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That's what I mean by needing to learn how. How the plaster mold, depends on the size, and undercuts. Undercuts are areas that would get caught inside the mold, where you could never pull it out without breaking first the model and then every time you tried to pour it.

So I'm thinking you're right. Resin or hydrastone pour. Hydrastone is one of the hardest plaster/cement formula's and it's not always easy to find without shipping it in.

What you might do is spend some time on http://polytek.com and http://smooth-on.com and watch their instructional videos. I think you'll come up with a solution just by learning more. For example, there are all sorts of fillers you can mix with clear or colored resins, to make it look like some other thing.

So many of the resin animal figures are resin and yet looks just like some sort of carved stone or marble. So I could talk all day but you can get all the information you need, concerning the resin formula's and applications on the sites of the manufacturer's of those formula's. So enjoy

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3 years ago#12
red46
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Oh yeah...and you can keep your model as is just seal it with something before proceeding with any kind of rubber mold. You can always call or email those folks for their suggestions on what to use to seal your model.

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3 years ago#13
mickpearson
Master
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HI. ID thought you had made a new one as yours cracked. and i must admit. iv.e never sealed damp clay and never had problems there is something new iv.e learned though iv.e heard it beforel. so ill try it myself. but i don.t do bad considering i taught myself and if i can do it anyone can.

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3 years ago#14
mickpearson
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AND im.e glad that red agrees with everything iv.e said so i cant be that bad for someone who is self taught

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