Safe Dial Part 2- The Casting

I cast the dial from Smooth Cast 325 using what they call a 'cold cast' technique, or what I call, schmooeying bronzing powder into the mold. This technique gives a metallic look to the resin. Here is how the process works.

Once I finished demolding, it was time to reassemble the mold.  The bumps and ridges formed by the cured rubber actually act as registration points for the mother mold. There are three important things to remember here. First, make sure the mold is seated well into the mother mold. The rubber should be solidly seated into the plasti-paste, without any wiggle.  The seam should be flush, and almost invisible, you don't want any leakage. Second, the mother mold should be clamped/taped/banded together- whatever it takes to get it secure and level. Leveling is very important for this casting, more so than usual because the back of the dial needs to sit flat on the safe, and the large surface area makes it harder to sand flat. Third, RELEASE RELEASE RELEASE. I used a liberal amount of Universal Mold Release in the mold before applying the bronzing powder. Release agent is important! Urethane resin is adhesive, and it will stick to all sorts of things- so I like to get some release agent pretty much anywhere I think I might get casting resin.

After the mold release was applied, I brushed bronzing powder into the mold. The idea here is that the resin will trap the powder in its surface and the finished casting will have a metallic look. Bronzing powder is another dangerous substance though, so before you use a soft brush to apply an even coat of powder to the inside of the mold, make sure to wear proper respiratory protection.

Once the bronzing powder was in place, it was time to pour the mold.  Following the directions, and wearing the proper protective equipment, I mixed the Smooth-Cast 325 and poured it slowly into the mold. It's always good to pour into the lowest point of the mold, and slowly allow the resin to rise. This will help prevent bubbles from forming in the casting. 

Once cured, I demolded the dial by gently removing the mother mold and peeling back the urethane rubber mold.  TA-DA!

 
I actually made two castings of this piece so that we could cut the center piece from the outside ring, and mount them to the safe so that the interior could spin.  To store the mold, I like to keep the mold in its mother mold, in a cool, dry place.

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Safe Dial- The Mold

So, I haven't blogged about many of my casting projects here on Fake n' Bake yet, even though apparently this is some sort of blog 'dedicated to casting and molding....blah blah blah.'  The reason is that fake food is just so much more fun. Sure, sure, casting is great, I love my job, but who doesn't love fake cocktails? Or fake TV dinners? Am I right? That said, casting and molding really are a large part of what I do, and there are some fascinating things to be done with casting and molding- so I thought I'd start to share a few fun things with you. 

This first little project is a dial for a safe.  We have a beautiful antique safe dial in stock, it just happens to be permanently attached to one of our other prop safes. So, what to do? Our carpenter, Erik (a props GENIUS) asked if I might lend a hand by taking a mold of the existing safe dial and casting a new resin dial for our new vaccuformed safe.

Materials: Visqueen, Universal Mold Release, Smooth-on Brush On 40, Smooth-on Sonite Wax, Smooth-on Plasti-paste, mixing containers and utensils


Safety Gear: Splash Goggles, Apron, Sleeves, Nitrile Gloves, Ventilation Hood, Respirator

I started by making sure that my original was clean, and by shielding the things that I did not want to cast. I placed a layer of visqueen on the safe, cutting a hole for the dial, and taping the edges of the opening down with packing tape.  Next, I applied a release agent. This is so incredibly important in casting and molding, especially when working with adhesive mold materials like urethane rubbers.  I applied two liberal coats of Universal Mold Release, making sure to cover all of the nooks and crannies of the original.

I made the mold out of two layers of Smooth-on Brush on 40.  I like the Brush-On 40 because it is brushable (who would have guessed), strong,  and just the right amount of flexible. Also, you can really glob it on to get nice thick, strong support for undercuts, and spread it thinner where you need more flexibility.  Be sure to read all of the directions carefully, and don't forget about the MSDS. Although they play it down in the literature, and although the Smooth-on guys do demos at trade shows without any Personal Protective Equipment, all two part urethanes are bad for you.  They contain sensitizers, which means that the chances of allergic reaction increase each time you are exposed to them. While you may never have a reaction, why risk it? I say, err on the side of safety. So yeah, read the MSDS, read the Technical Bulletins, and protect yourself.

Once both layers of the mold were cured (I tinted the second to ensure coverage, hence the pink), I began on the mother mold.  Before smearing on the Plasti-Paste, it was time to put on another release agent.Smooth-on Sonite Wax is a petroleum based wax that works as an excellent release between the cured Brush-On Rubber and the Plasti Paste. Because the rubber will not be fully smooth, the Plasti-Paste can register into all of those little nooks and crannies- making it difficult to de-mold.  The Sonite Wax is thick and slippery, and helps the de-mold process immensely.  I made the mother mold with Smooth-On Plasti-Paste, a thick, goopy two part plastic which hardens into a strong mother mold.  This is another Urethane, so use that safety gear! Also, the Plasti-Paste can become very sharp if it is peaky when it dries, so try to smooth it as much as possible. The mother mold is made in two parts to allow it to come off of the mold easily. I waited for the first half to cure, then applied more Sonite Wax and spread on the second half.

Once the mother mold is cured, it's time to de-mold. I removed the mother mold, and then used an X-Acto knife to carefully cut a slit in the mold....just enough to allow the head of the safe dial to slip out. Any seam in your mold is a potential flaw in your casting, so it's important to plan ahead and cut carefully.

Next, the casting.....stay tuned!

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