materials for resin casting - where and what?

[Sulla]

I would like to play around with some small resin castings. I have scratch built a trek hyprospray and sculpted a strip of gold pressed latinum I would like to duplicate in solid resin. I chose these two as my first forays into resin casting for thier size, simplicity, and to get some experience working with both 1 part and 2 part molds.

I own, have read, and re-read "The Prop Builders Molding & Casting Handbook." I have read a few tutorials on-line and feel ready to give it a try.

My question: What materials should I buy (plaster or rubber mold?) and should I bother with a 'starter kit' from some place like Hobbytown USA, or should I just go buy the chemecals and clay and go at it?

Also, I am thinking that a simple plaster mold for the latinum would work as it has no strange undercuts; but with it's many fine details, would a rubber mold work better?

 

[blufive]

I get my rubber from:

siliconesinc.com

I use GI1000 base and GI uh... Something else for the activator.



For resin, my personal preference is the Smooth Cast line from smoothon.com .

Each resin is a little different so make your choice based on the color you want, shrinkage and pot life. Mixing ratio may also play a factor in your choice since some resins are 1:1 (easy cheesy) and some are 100:75 or any other variation.

You can cast resin without a pressure pot or vacuum chamber. You can pop the surface bubbles (with resin) with a flame. Then, slowly make your pour.

With rubber (RTV), you will need a vacuum chamber to remove the air bubbles. If you don't, you will have a mold that is full of little pin holes.

 

[Sulla]

Thanks, blufive What mold releases do you suggest, and do oil based clays mess with the rubber mold material? Easy is the way I'd like to go at the beginning, so a 1:1 resin cast with a silicone rubber mold sounds best, am I right about this?

Here's how I have it in my head so far:
Build my mold box (with clay, foam board, wood, legos, what ever), place my original in on the bottom of the mold box for the latinum 1-part casting, and do the clay for the 2 halves of the hypo-spray 2-part casting. Mix and pour my mold over the original. Let it cure. Should I use rubber or plaster? I'd like to minimize effort while I get used to this, but I also don;t have a vacuum chamber. Can I not use rubber, stirred thoroughly but gently so as to avoid bubbles, then pour and tap to remove more?

Once the mold is cured and the originals have been removed, clean the mold, apply mold release, and after mixing the resin per manufacturer instructions (carefully so as to minimize bubble) pour into my mold starting at the lowest point. Tap the resin filled mold to hopefully remove trapped air on the surface of the resin casting before it cures.

 

[blufive]

You're on the right track.

I use Mann 400 available at smoothon.com .

I would use silicone instead of plaster. The only time I've ever used plaster is when making a large mold that requires a jacket (shell) to save money on the RTV.

You can't get the air out of RTV with any method besides vacuuming, that I'm aware of. Someone please correct me if I'm wrong.

micromark.com sells a rubber that doesn't require degassing BUT it is not a good product and you'll only get a few pulls from it.

Thanks, blufive What mold releases do you suggest, and do oil based clays mess with the rubber mold material? Easy is the way I'd like to go at the beginning, so a 1:1 resin cast with a silicone rubber mold sounds best, am I right about this?

Here's how I have it in my head so far:
Build my mold box (with clay, foam board, wood, legos, what ever), place my original in on the bottom of the mold box for the latinum 1-part casting, and do the clay for the 2 halves of the hypo-spray 2-part casting. Mix and pour my mold over the original. Let it cure. Should I use rubber or plaster? I'd like to minimize effort while I get used to this, but I also don;t have a vacuum chamber. Can I not use rubber, stirred thoroughly but gently so as to avoid bubbles, then pour and tap to remove more?

Once the mold is cured and the originals have been removed, clean the mold, apply mold release, and after mixing the resin per manufacturer instructions (carefully so as to minimize bubble) pour into my mold starting at the lowest point. Tap the resin filled mold to hopefully remove trapped air on the surface of the resin casting before it cures.

 

[exoray]

You can't get the air out of RTV with any method besides vacuuming, that I'm aware of. Someone please correct me if I'm wrong.

For most molds if you pour from a distant height (at least a foot or two) with a VERY fine (think spider web like) stream into the mold almost all the bubbles of any size will be eliminated...

For the average mold this will be fine and work out without any additional degassing...

My suggestion is to get at starter kit from either Smooth On or Alumilite and simply jump in after reading the instructions...

Alumilite also has some great pictorial "How To's" on their site give them a look...

www.alumilite.com

And last but not least, stick with silicone as your molding material for right now, other molding mediums have their place but silicone is by far the most universal and user friendly...

 

[blufive]

I forgot about that method! I'm normally in too much of a hurry to pour the RTV. Making a stream thin enough to release most of the bubbles takes FOREVER!

:lol

 

[Sulla]

Sweet, thanks you two. I can't wait to make a mess, waste some $, and figure ths stuff out.

Once I get a bunch of casting under my belt, I'll have to try vacuforming.:lol

this looks promissing:
http://www.alumilite.com/ProdDetail.cfm?Category=Starter Kits&Name=Super Casting Kit

Awesome pictoral tutorials too, thanks again for the link and advice.

 

[exoray]

Making a stream thin enough to release most of the bubbles takes FOREVER!

Yeah you need to zone out while you are doing it as it does get boring real quick, but it's effective and for small molds not too bad...

And that starter kit you linked to is a good start, it has enough stuff for you to get your feet wet and give things a spin...

With that kit, a sheet of foam board, some gloves, disposable cups and a hot glue gun you will be well on your way...

 

[Sulla]

With that kit, a sheet of foam board, some gloves, disposable cups and a hot glue gun you will be well on your way...

Perfect, I have all of those things... time to dive in.

 

[Chingon]

For most molds if you pour from a distant height (at least a foot or two) with a VERY fine (think spider web like) stream into the mold almost all the bubbles of any size will be eliminated...

Yeah, the "bombs away" method. Thats what I used to pour the silicone for my han in carbonite/chocolate molds and they came out pretty good!

 

[Sulla]

If I get that starter kit, I want to make sure my latinum sculpt will hold up. What type of clay should I use? I can make another sculpt of this piece pretty easily.

 

[Sulla]

How about this from the same provider as the starter kit?

http://www.alumilite.com/ProdDetail.cfm?Category=Dyes - Fillers&Name=Super Sculpey

 

[exoray]

If I get that starter kit, I want to make sure my latinum sculpt will hold up. What type of clay should I use? I can make another sculpt of this piece pretty easily.

Just use sulfur free modeling clay... There are lots of different brands...

 

[Sulla]

Just use sulfur free modeling clay... There are lots of different brands...

Thanks, your help has been indispensable. I like these, which of the following should I use to keep a good shape through casting with some small details on my sculpt?

Should I use 'natural firm'?
http://www.utrechtart.com/dsp_view_product.cfm?classId=2010&subclassID=201012&brandname=&item=69812

Or 'natural regular'?
http://www.utrechtart.com/dsp_view_product.cfm?classId=2010&subclassID=201012&brandname=&item=69814

or 'natural set'?
http://www.utrechtart.com/dsp_view_product.cfm?classId=2010&subclassID=201012&brandname=&item=69816

or 'primary set'
http://www.utrechtart.com/dsp_view_product.cfm?classId=2010&subclassID=201012&brandname=&item=69815

 

[Djinn]

I have heard that you shouldn't use plastelina modeling clay, is that true when making an alumilite mold?

 

[blufive]

I use Kleen Klay from micromark.com for laying clay beds but I haven't tried sculpting with it.

You can always use Sculpey. Once it has been baked, it can make a good master.

 

[exoray]

I have heard that you shouldn't use plastelina modeling clay, is that true when making an alumilite mold?

You should just make note if it has sulfur in it, avoid ones with sulfur...

Sulla the ones you linked all appear to be just fine...

 

[Sulla]

Very cool. I bought a couple of different kinds of clay and the starter kit. I have my eye on a sculpting tool kit (my old one is a set of styrene rods with speciallty cut/filed ends.) I figured, If I am going to do the casting right, I may as well get some tools for sculpting too.

Thanks again everyone for your help! I'll keep you all updated on this little first cast experiment.