Copying Beaky heads using a hybrid 1-2 piece mold

[Duymon]

I was asked how I made my beaky head recasts without the crazy bubbles and without a pressure chamber. This technique is a little messy while casting and the molds wear out a lot-faster due to extra movement on the silicone. However, the results are pretty good so it's a good tech for small parts-runs.

Here's a quick write-up with pics

Items needed:

• RTV Silicone (I use Smooth-on OOMOO30)
• Plastalina Polymer clay (I use This)
• Something to make mold walls (i use legos)
• Mold Release
• Resin (I use Smooth-Cast 300)
• Plastic rod for gating
• Gloves for casting unless you wanna be nurgle-ey with resin all over your hands

I usually keep a set of masters that never go into my bits box.

http://imgur.com/1FDsUuo.jpg

Today I'll by casting two regular beaky heads + a targeting eye head for good measure. I've got my masters cleaned up and Plastic rod glued on. Notice how I trimmed / sanded the plastic rod so it goes at an angle and matches up with the the "rim" on the back of the heads

http://imgur.com/wQ3y2pQ.jpg

The next step is to prepare a small mold-box. I use legos and have put a small 1/4" layer of plastaline clay in the bottom and boxed it on the sides with lego pieces

http://imgur.com/bWGGyGO.jpg

Afterwards the heads are inserted so the heads are in the middle of the mold box. They are placed so that just the neck joint goes into the clay. My goal is to make the mold-line along the bottom of the heads to minimize loss of detail.

http://imgur.com/9Xa7i4r.jpg

Because I hate wasting Silcone (it's quite pricey) I transfer my silicone into squeeze bottles I bought elsewhere. I'll be mixing it in a tiny party-shot cup.

http://imgur.com/SX9dwmK.jpg

Silicone mixed and poured. To minimize airbubbles on the pieces themselves you need to tilt the whole thing little by little. I also put my electric toothbrush handle on the the bottom while I tilt to add some strong vibration.

http://imgur.com/zV9MnMK.jpg

First-half cured. Carefully remove the walls and the clay

http://imgur.com/TRvTSnk.jpg

After cleaning up all the clay, mold looks like this. I draw a line on the bottom 1/4 of the mold, just under the nose points

http://imgur.com/1bVQX8P.jpg

Here's where things change up and we use a hybrid mold technique. Normal 2-piece molds put mold release on the entire 1st half and have two separate pieces. I only put mold release on 3/4 of the 1st half. This causes the 2nd half to stick on the bottom half and creates a "single piece" mold.

The advantage is I can keep the mold open when I first pour, and close it up as I fill it with resin. This is how I get 0-bubble casts.

http://imgur.com/yGFUZEk.jpg

After mold-release dries, 2nd half poured

http://imgur.com/7Ouo1Lp.jpg

After curing, mold walls removed and we're able to open up the mold and remove the masters. Since the bottom is stuck together we get 100% perfect alignment everytime we cast thereafter.

http://imgur.com/M6LSCjM.jpg

After that we just mix up some resin and pour. At first the mold is kept open and while resin is poured, slowly close the mold. WEAR GLOVES

http://imgur.com/8hLNyfm.jpg

After resin cures, demold and you'll have small flash or even mold-lines along the bottom of your beaky helmets. A simple knife flick and they are gone.

How they look after demold

http://imgur.com/cuCl3fB.jpg

Enjoy your bubble-less beaky helmets (black wash added to emphasize details. I just noticed there's a tiny bit of flash on the left side that needs to be cleaned off lol)

http://imgur.com/V2MnTXS.jpg

[Canadian_F_H]

That turned out well.

[JeffTibbetts]

Wow. Some seriously great tips in this post. Thanks so much for sharing! I'm adding an electric tooth brush to my shopping list for sure. Very clever to make a 1.5 part mold. I still don't know how the noses don't end up with bubbles, but I'll take your word for it.

[Duymon]

Yeah, the reason the noses don't get mad bubbles is because in this setup the resin has many more places to go when the mold is opened so the bubbles don't have a place to snugly fit into the nose-tip area. As the resin is poured and the mold closed the air bubbles flow out with the resin and/or up thru the gates.

[Paradigm]

The 3/4 split mold is a cool idea. I've been cutting my molds back to 3/4 but you risk damaging the parts that way. This way, you don't damage the original and get all the benefits. 

Much appreciated tutorial.

[JeffTibbetts]

Oh, I see! So, you sort of deliberately create a flash wall? That's interesting. Another thing I'd never considered. 

[Doctor Perils]

Great tutorial, short and to the point, but with lots of great tips and techniques. I'll definitely be giving this a go when I get round to it :)

 

(Now I've just got to find a way of applying it to Samael's Jetbike... :P)

[Res Ipsa Loquitur]

You can also eliminate bubbles (from the mold at least) by painting a thin layer of the silicone over the part to be cast. It will 'stick' seamlessly to the poured silicone and you're guaranteed to not end up with pricey, but useless, molds.

[Sol_Invictus]

Well, I'll definitely be giving the 3/4 split technique a try on my next mold. Thank you, sir, for a great little tutorial. 

[Joe]

I might have to give this a try with some MKIV heads. Out of curiosity, do you have any advice on performing similar moulds when it comes to torsos?

[Hrolf the Cunning]

As someone that has spent a fair amount of time casting and lots of wasted silicon in the learning process, this is an excellent little tutorial both in terms of quality of outcome but also practicality and efficient use of products. Good work mate.