Casting of the Twins - wip

[RollaJedi]

ok, no problem! 

[Phrubruh]

Here is an updated picture of my casting attempts. The silcone is poured over the two test subjects. Now I'm in the middle of waiting for it to harden.

It kind of looks like somebody blew their nose and I wanted to keep it.

[BrentS]

Hey Phruby, What kind of "sprue" holes will there be with these molds.  When I've made molds with silicon it looks like snot too - we must be doing something right!

[Phrubruh]

I guess I'm on the right track. Before I put the silcone on the figures, I covered them with petrolien jelly to make it easy to get them out. Here are pictures of the holes.




I forced the piece thru the spew holes and got a pretty good impression from both pieces. I'll try casting them on monday. I'll probably have a ton of bubbles. We'll see.

[BrentS]

I guess I'm on the right track. Before I put the silcone on the figures, I covered them with petrolien jelly to make it easy to get them out. Here are pictures of the holes.

From the molds I've made, I haven't "pretreated" any of this plastic.  It just slips right out of the silicon (much better than latex!!)

[CHEWIE]

Man, those look like nasty, vomited up eggs!   

Really, this is interesting to see how you go about making these.  Not something I'd be comfortable with trying at all.

 

[Phrubruh]

Got to remember I have no clue what I'm doing. Just following instructions and tecniques.

[Darth_Ennis]

Well, its looking pretty good so far. Disgusting, but good. I missed out on the twins myself, I wouldnt mind getting a set later on if youre able.

[Glassman6]

Yeah Phruby, you look like you are right on track.
From the first photo it looks like you just had the pieces laying
on cardboard. But you did use a sprew. Good work.

Remember, the vasaline, if apllied to heavy will mess up the mold.
You will be molding little vasiline deposites and not the just the figure details.

I'll tune intomorrow to check out the progress.


Have you tried a 2 part mold yet?

[Phrubruh]

Not yet. I used a q-tip to put the vasiline on. Do I need to cote the inside of the mold with something before pouring in the casting material? I think the hardest part so far was to keep the silcone on the piece while I was waiting for it to harden. I had to keep scooping it back on.

[Jesse James]

I've not generally had to coat things as you did Paul, though when I have, I've used THINNED vaseline...  I thin it with straight gasoline out of a can.  The only times I've had to use it is to keep two halves of a mold (for 2-part mold making) separate...

[Phrubruh]

Your joking right? Gasoline? Your scaring me Jesse.

[Jesse James]

Nope, not at all.

Gasoline thins out vaseline (sp?) well...  It makes a much more "manageable" material for working with latex's...  I've had no adverse effects to casts either, or plastic pieces I've been making molds of, so it's a cheap option...

now, bare in mind I've NOT used that as a de-molding product either...  I've used it as a barrier when wanting to make two separate halves of a mold.  It keeps the RTV Silicone from bonding, acting as a very thin, but not runny, barrier for the Silicone...  It's something I figured out while I was practicing making 2-part molds a while back...  Works fine.  I've never coated the inside of a mold with the materials and cast a head then de-molded it with that concoction, but I don't think it would harm it...  As with everything casting though I've found that a lot of trial and error is in order when you're starting out.

I've had little use for de-molding agents, though there will come a point where your mold is prone to sticking to casts...  Usually after a number of molds.  The de-molding agents that are out there then usually help keep that from happening (it's usually a sharp detail on what you're casting that'll actually stick to the mold and tear it while you're trying to de-mold the cast).  Some people de-mold using talc powder to help molds release (also fills possible air bubbles well in your mold so there aren't marks on the cast), others use release agents you can get from casting suppliers, and I have read the thinned vaseline (with gasoline) can work if done right...  It's an option at least.

[BrentS]

In my limited experience, you only need demolding agents for 2 piece molds?  Would the experts concur?  Like I've said before, with the silicon one piece molds, I haven't had any problems (other than tearing of thin sections) with removing the original or cast pieces.

[Jesse James]

Well, the RTV Silicone mold will break down, and eventually, after so many uses (depends on the quality, etc.) it'll start sticking to casts and tearing...  My first mold I made was a POnda Baba head (few undercuts, nice and rounded, etc.).  I probably pulled 50 casts from that mold in practice and after a while, a blue piece was here and there stuck to the casts...  It was part of the inside of the mold.

The release agents are just something that helps the mold last longer...  If you're pulling hundreds of casts, which you may be, it's useful to an extent...

The only thing I've used the vaseline/gasoline mix for is to keep halves of a 2-part mold from sticking together while making the mold...  This is just a brief rundown of what I mean for those unsure...

-I make my mold box and fill the bottom with sculpey III, and with the head (or whatever) inside the clay HALF way.

-I fill the mold box, covering the OTHER half of the head that's exposed out of the clay, with Silicone...  It cures.

-I remove the clay and turn the cured silicone half of the mold over into the mold box so it's now on the bottom...  The exposed half of the head is facing up now instead of down before.

-I then put the THINNED gasoline/vaseline mixture over the top of the silicone (not the head, though it doesn't matter if it gets on there so long as it isn't thick and distorting the details of what I'm trying to cast).

-I pour more silicone in the mold box filling it up again....  It cures.

-I demold, and the gas/vas mix keeps the two halves from sticking.  They separate perfectly...  The head doesn't have to be "worked" out of the mold, so there's no risk of stretching the mold or losing detail there...  It's pretty perfect, just more work, and generally used for parts with sharp undercuts and complex designs.