RTV rubber

[Delaton]

Brushable Latex Rubber is available at Michael's stores in the adhesive & glue aisle.  Latex usually has to be 3 or 4 layers thick to be an effective mold and hold its shape.  I have to stress that if you're casting any part that must be cast through a small hole, demolding will most likely crush the cast because the latex will be too strong.

[Joe]

o.k. well I decided to go with the rtv.....now where is it I can find it in a store around here?I know im hasty.

[Ryan]

Like I said earlier, online will probably be your best bet.

[Delaton]

Unless you have access to a Pearl AND happen to catch them while they actually have it in stock, you need to go online.  Pearl carries Smooth-On in their stores but they only order it one case or so at a time.  When they run out, it could be weeks for a new shipment.  To add to it, Pearl doesn't list it online.

www.smoothon.com
www.polytek.com

Those are my suggestions.

[Joe]

PEARL-its a store right?Is there one in MA (delaton im pointing your way){prefebly near saugus}

[Delaton]

Yes, near Boston.  The Pearl stores I used to get my supplies at were in NJ.  A friend used to buy them out for both of us from time to time.

[RollaJedi]

Ok, I'm gettin pretty frustrated.  For a 2 part mold, I put the master into the rtv mix trying to make it about half way in.  I do this after it has firmed up a little so it doesnt sink (about a couple minutes).  But, when I'm done with this step and come back to it for the top part of my mold, it has sunk down further into the stuff, sometimes burying parts!  SO, I usually have a really shallow indention in my top mold layer.  Any suggestions?

[Glassman6]

I wait 10 minutes before i place the pieces in.
When i pour, i take a spoon and rub it into the crevases of the side thats going face down.
SO when i stick it in 10 minutes later I dont have to worrry about RTV getting into the tiny places and
making airbubbles.
By this time you are pretty much pusing it in. SO you can stop when its as deep as you want it.

Another trick, is get a piece of scotch tape. long enough to run across your mold box.
and let the tape hold the piece from sinking all the way.

[RollaJedi]

cool!  That should really help!  Your idea on the casting you commented on (not thick enough and dripping out before it was flipped) worked well too, just to let ya know.    Thanks!

[Smartypants1635]

I got a perfect cast from a 2 part mold yesterday, sadly I went back and revised my sculpt. So I'm making a new mold as we speak.

[RollaJedi]

ok, I waited 10 minutes last night and it still was goopy, so I waited some more.  I waited a total of about 30 minutes and it wasnt much better, so I stuck the stuff in there.  Naturally, it sank 3/4 of the way in some places.

Will the molds still work if they are like this?  If the top half is just a little indention of where the part jutted out some, can I still put casting stuff in there to make the cast?

[Smartypants1635]

yeah, that happens to me all the time. Still works.

[Glassman6]

Yes it will still work. If you get a line across the piece, it just wont be down the middle.
I have quite a few molds with pieces that went 3/4 of the way in.

[bikeridetony]

Hi there,

I really need to make some molds for some Kubricks.  If you haven't heard of them, they're rare collectible Japanese figures.  I really only need the hair piece done which is one small piece.  Is there anyway I can pay you to do these?  I'll need about 40 in the end.  Let me know if you are interested or know anyone who's good and willing .  Thanks!

Tony

[Straxus]

For those making two part molds for helmets this tutorial will help.
Now the tutorial is not on making molds for helmets specificly, but will help give ideas.
Dan Perez Studios molding and casting tutorials

If you dont have a pressure pot, just use the air vents ideas mentioned in the tutorial using toothpics glued to small areas to allow air to squeeze out.

Depending on the RTV rubber used, sometimes before pouring the mold, use a old paint brush to make sure small crevaces are filled with mold material and air bubbles on the surface are removed before pouring. I found with my helmet casts this saves alot of hassles and makes sure molds work great first time arround. (This again is for those who dont have a pressure pot.)

Also a technique to use if making latex molds of head casts, make small cuts with an exacto knife in the location of the nose, chin, ears or any other part that might suffer air bubble problems. Make sure it is a small clean cut with a sharp exacto. When pouring casting resin it helps push the air bubbles out, and if its a small incision the casting resin should not leak out. I have been doing this for a while with alot of success.

As someone who has been using Rubber Urethane RTV for the last year, who has now started using silicone rubber, honestly, save the hassle and be patient and get the right stuff for the job. I am a horribly impatient person. I went the route of getting anything I could to start molding and casting right away and it was not only way more expensive in the long run but caused far far more frustration than it was worth. Check out Smooth-Ons distributer links. In many cases there is a company that can ship the stuff faster and cheaper than ordering it directly from the store. (Or the other mold making companies mentioned in this thread.)
Though if you MUST have something right away, another store you can check and see if its in your area is TAP plastics. Its not the greatest, but its out there. Their casting resin sucks for anything other than prototype work.

Well enough of my rambling on the subject...