Release agent for smoothcast 300

[this is haji]

you do not need a release agent when casting in rebound 25 correct?

What about casting in a plastic mold. I want to cast my vacuformed visor and used it as a mold.
I coated it in pertroluem jelly and only poured a very tiny bit of smoothcast. After it turned white i tried peeling it but it felt like it stuck so i had to bend the plastic visor quite a bit to pop it out.

Is their a release agent for making easier to pop out? i was planning on use low detailed vacuform peices as molds

forgot the mention that it only cured for 15 mintues. could that have been the issue?

and has anyone tried this before

 

[Xtreme TACTICS 101]

You don’t need a release agent for Rebound 25. In my experience, if you use one with Smooth-Cast 300, residue from the release agent is left in the Smooth -Cast and silicone therefore making priming, painting and any cleanup work a pain for the cast you used the release agent in, and about 20 casts afterwards.

I have never heard of casting from a vacuum-formed armour part before, however if you wish to experiment, try using Smooth-on’s Universal Mold Release. It is a spray on release, but do not over apply. Spray it into the mold, and use a clean towel/rag to wipe it around to it is in every nook and cranny, and there are no pools of excess release.

I have had a lot of trouble with Smooth-on’s Smooth-cast 300 and Universal Mold Release, explaining why I switched to casting in a polyester gelcoat, resin and fiberglass. However, I have not had any problems with Smooth-Cast 320. Paint, primer and bondo seem to bond very well to it. It may be because of a chemical property concentrate that is far higher in the 320 then the 300 (The ability to accept tinting agents far better then the Smooth-Cast 320).

Anyhow, good luck with the molding and casting of your Weta ODST helmet. It looks very good!

Stay frosty,

Jake
Xtreme TACTICS 101

 

[this is haji]

Alright thanks alot for the information, I tried it again but a smaller ammount. I wanna it's safe if i filled the whole thing, it would have popped out easier but i end snapping my visor getting a tiny patch out

I will give the mold release a try but I did the calculation and vacuforming polystyrene sheets and fiberglassing will be cheaper then Attempting to cast in it. Most of my odst armor parts are individual peices to put together to form one just to insure i get as much detail as i can

Thanks once again !

 

[Beau Nidle]

You don’t need a release agent for Rebound 25. In my experience, if you use one with Smooth-Cast 300, residue from the release agent is left in the Smooth -Cast and silicone therefore making priming, painting and any cleanup work a pain for the cast you used the release agent in, and about 20 casts afterwards.

Just to add to this, giving the cast a scrub with an abrasive pad and hot soapy water can help get rid of this residue if you do want to use a mold release (it does prolong the life of the mold). It's not perfect, and you may need to do it a couple of times but it does make it easier to paint.

 

[beaker]

From our FAQ section:
You’ve made the perfect mold and have just poured Smooth-Cast liquid plastic into the mold to make a reproduction. The plastic cures, and you demold the piece to reveal a casting that looks exactly like the original. Your next step is to paint the casting for outdoor display, but when you try to apply the paint, it beads up on the casting surface and won’t stick.

Urethane plastics can be hard to paint, and there are a number of variables that can affect the outcome. Using a release agent to release the casting from the mold, for example, makes painting a casting almost impossible. Removing release agent from the casting surface can be difficult and is another labor step.

If you are using a urethane rubber mold and casting urethane resin, you must use a release agent to facilitate demold. Using a silicone rubber mold without release agent limits the production life of the mold by 1/2 if you are casting urethane resin.

There are a couple of ways to get the benefits of using a release agent and still have a casting ready for painting following demold.

Powder Coating Technique - Powder coating the mold with Ure-Fil 7, baby powder or talc following the application of a release agent. Here is how it works;
Prior to casting the resin, Ease Release 200 is applied to the mold followed by a powder coating of Ure-Fil 7.

An air hose is used to blow any excess powder from the mold. The urethane resin is then cast into the mold.

The casting comes out of the mold with a dry, matte finish. An auto body primer is applied, followed by an acrylic paint and finally an acrylic sealer. The major advantage to powder coating is that there is no release agent to remove when the casting comes out of the mold. Models can be immediately primed and painted.

Apply Primer To The Mold Surface - The other way is to use a spray primer. Here’s how it works:
Following the application of a release agent, an auto body primer is applied to the mold cavity. Casting resin is then mixed and poured or sprayed. The auto body primer bonds to the casting’s surface and comes out of the mold ready for painting.

Customers contact us regularly asking which primer works best as a foundation for painting their Smooth-On plastic castings. To settle the question once and for all, we tested over 30 aerosol primers and found that most did not work, or worked poorly at best.

The low-quality primer would “bead up” on the surface of the casting.

Whether applied to the rubber mold surface or applied to cured castings (no release agent used), two primers did stand out, providing excellent adhesion and the best for painting.

Plasti-Kote™ Sandable Primer – can be found at Auto Zone and other auto supply stores in the U.S. Contact: Plasti-Kote in Medina, OH Tel. 800 431 5928 or www.plasti-kote.com

Bulldog™ Adhesion Promoter - Contact: W.M. Barr Co. in Memphis, TN Tel. 800 398 3892 or www.wmbarr.com. Or order online at www.levineautoparts.com