2 quick noob questions

[active84u]

Having never sculpted or cast anything, I thought I would have a go at making a facehugger.
I decided to sculpt it in sections as I know Im going to struggle with making moulds from it.

I have used oil based clay to sculpt a tail, now Im not sure what is the best way to make the mold.
I guess a 2 part mould will be the way to go due to removing the scultp?

Any suggestions as how to hold the scultp in place while the first half of the mould sets and what to put on the split point of the mould before I pour the second half?

I dont really want to make a mould I cant get the sculpt out of. Getting the latex cast out should be ok with the mould closed by just pulling on the wide end of the tail.

Cheers
Vince

 

[hez1]

Without seeing the sculpt it's pretty hard to make a recommendation. However, I would heartily recommend a trip to www.smooth-on.com where they have some great tutorials on mold making. Almost every silicone they sell has photo tutorials of different objects and how they were molded.

 

[active84u]

Without seeing the sculpt it's pretty hard to make a recommendation. However, I would heartily recommend a trip to www.smooth-on.com where they have some great tutorials on mold making. Almost every silicone they sell has photo tutorials of different objects and how they were molded.

Cheers Hez. Couple of shots from my mob. Im going to make a plaster mould then cast in latex, cheap and wiggly so will behave as it should. If it comes out ok, am going to make one with a wire armature inside to make it poseable.

Any tips (to save me having to start from scratch again) greatfully recieved ;-)

Thanks
Vince

 

[Alieneater]

It really depends on what you want to cast the final piece is,the general rule is rigid mold-flexibal casting material,flexible mold-rigid casting material.For anything latex I always use ultra cal 30 but you could easily use hyrdrocal if its easier to find for you...Hope this helps!
Take care,Hector

 

[active84u]

It really depends on what you want to cast the final piece is,the general rule is rigid mold-flexibal casting material,flexible mold-rigid casting material.For anything latex I always use ultra cal 30 but you could easily use hyrdrocal if its easier to find for you...Hope this helps!
Take care,Hector

Thanks Hector.

I have some Crystacal R which is the same as Hydrocal I think. I am just concerned how to support the sculpt while I pour the first half underneath and and how to stop the top of the first half of the mould sticking to the second half when I pour it. How thick should the mould be? Its quite a long shape (27 inches)

It would be funny (eventually) if the sculpt was 'stuck' but this is my first go so would like to get something from the process other than frustration ;-)

Thanks
Vince

 

[hez1]

Well, I'm far from an expert on molding with ultracal or any gypsum, but here's what I'd do...not entirely sure about which order I'd do the first two in though.

1) Build a box around your sculpt from perspex or similar.

2) Pack clay around the sculpt so that only the top half of it is visible, and then make some indentations in the new clay that will work as mold keys when the second lot of gypsum is added later.

3) Pour on the ultracal/hydrocal, whatever you're using, and totally cover the sculpt.

4) Remove box, flip the sculpt and half mold upsidedown so that the uncovered half is on top. Remove the clay that you packed around it. Build the box around it again.

5) Rub vaseline on the ultracal where any new mold material will touch it and potentially bond. This will act as a release agent.

6) Pour more ultracal, again completely covering the sculpt.

7) Once cured, you should be able to remove the box and pull the two mold halves apart pretty easily, and thanks to your mold keys from step 2, be able to line them up again later. However, from what I know, it's unlikely you'll be able to remove your original sculpt without ruining it.

Hopefully one of the guys who has more experience with gypsum molding will chime in, but that's how I would take a stab at it. Good luck!

 

[active84u]

2) Pack clay around the sculpt so that only the top half of it is visible, and then make some indentations in the new clay that will work as mold keys when the second lot of gypsum is added later.

Cheers Hez, makes perfect sense but, wont the clay stick to the sculpt?

Really want to get this going so might try supporting the scultp on something then pouring the first half. Should be plain sailing from there with the help/advice recieved. Will post up the outcome ;-)

Thanks
Vince

 

[crawjaw]

Assuming it's a latex copy of your sculpt you're after then hez's method is spot on. You only get one stab at it as the sculpt will get wrecked when you remove the mould. If on the other hand you want a resin or plaster replica you can mould either with silicone or latex. However it would be better done in silicone as a 2 piece mould is needed and lining up multiple latex moulds isn't a great idea. You should also get a second stab at it if required, as the sculpt should survive the moulding intact.

 

[active84u]

Assuming it's a latex copy of your sculpt you're after then hez's method is spot on. You only get one stab at it as the sculpt will get wrecked when you remove the mould. If on the other hand you want a resin or plaster replica you can mould either with silicone or latex. However it would be better done in silicone as a 2 piece mould is needed and lining up multiple latex moulds isn't a great idea. You should also get a second stab at it if required, as the sculpt should survive the moulding intact.

Yes Im after a latex copy of my sculpt. Not a solid copy as it would be too stiff, but will pour the latex in and let it dwell for 15/20 mins before emptying out again. Should give a good strong 'skin' when dry.

I still cant see how I can perform 'step 2' without mucking up the sculpt, am I missing something?

Thanks
Vince

 

[crawjaw]

As you have used oil based clay you can lightly surround the bottom half of your sculpt with water based clay. You only need to get the upper surface of the clays in close contact. Buiding a support with wooden or foam blocks will cut down on the amount of clay you need to use. Just be careful not to mark the surface of your sculpt when smoothing the water clay.
There's masses of info online but here's a link that will give you an idea.
Mould making

 

[active84u]

well, my first ever sculpt/mold/cast has been a bit of a learning curve.
while not a complete failure, I have some changes to make to what I did.

 

[xdmray]

looks good man. when self educating there is always a bit of a curve. practice, practice practice and you will get there. more than anything, patience. don't rush any of the molding process and you will be more successful. and always remember release agent before pouring the second half!!

Cheers

 

[Elkman]

well, my first ever sculpt/mold/cast has been a bit of a learning curve.
while not a complete failure, I have some changes to make to what I did.

I don't see any problems with it. There's always a learning curve when doing a new technique -- for example, when I was doing the gloves for my Gamera costume, I mixed the Ultracal 30 too thin and didn't use enough burlap, and I broke the mold. I had to fix the sculpture and cast it again. Fortunately, nothing was permanently screwed up.

Did you have any questions or things that went wrong? Maybe someone can give some advice.

 

[active84u]

Thanks to those that gave enough advice to save this going in the bin. The cast is a little heavy at the end of the tail where the latex is almost solid and a couple of small thin spots that were caused by a sharp edge in the mold.

I have the body to finish sculpting and the fingers to do.


thanks again for the help.

 

[Uratz]

Cheers Hez, makes perfect sense but, wont the clay stick to the sculpt?

You can spray clear coat over your oil or water based clay. Then the clay will remove easier from the plaster mold