Binaural dummy-head microphone [Part 3 – Creating Silicone Ears]

I mentioned it in the Plaster cast section, but I’ll say it again. Be super careful in choosing a clear lacquer to seal the plaster as it can severely screw up this stage.

There are two main sorts of silicone:

1) Tin: Virtually immune to inhibition issues, it’ll happily cure in a day or so, is super flexible, easy to work with and my stuff came in a lovely shade of blue. However it’s got a shelf-life once cured and will begin to break down after a few years. This is obviously is no good for a device you’ll hopefully be using for years to come.

2) Platinum: It’s more expensive but it’s really the only choice. It’ll last indefinitely and is really resistant to most things once fully cured. It is prone to inhibition though. In my case, the Plasti-Kote clear sealant I used on the plaster ear casts stopped it curing properly, and even now the moulds I made using Plasti-Kote sealer are tacky to the touch.

Do this bit properly, don’t be cheap like me, because you will end up throwing money away. If you invest properly it will be well worth it. If you really want to throw your money away I’ll give you my paypal details.

I used:

Alex Tiranti Addition Cure 33 Silicone

Mann Ease Release 200 (I got mine at 4D Model Shop in London)

There are plenty of instructions online about working with silicone. Look on Youtube, those guys can teach you better than I can. I won’t lecture you, just do proper research.

These photos are from when I made moulds with Tin silicone as I’ve not taken photos of the Platinum casts yet. The casting process is essentially the same though.

Spray your ears with Ease Release, following the instructions on the can. Wrap some cardboard in plastic wrap, spray that as well, and then build a well around the ears. Seal the bottom of the whole thing up with plastic wrap so no silicone leaks out. Very, very slowly in a very thin line start filling the well up from the lowest point until the ear is covered. It’s vital you avoid air bubbles so take care here, bearing in mind the silicone will start to set within about 20 minutes.

There. Leave them for the appropriate amount of time (about 6 hours for Platinum) and remove the cardboard etc.

Carefully remove the moulds from the ears, bearing in mind plaster is fragile, so do be gentle. It should come away easily enough. I’m not sure it’s essential but I left mine exposed to the air for a few days just to be 100% sure they were done curing.

You’ll have two moulds now. Wash them with some warm water and dish soap and be sure to rinse them and dry them properly. Anything left behind on the surface is a potential inhibitor. The process here is pretty similar to creating the moulds:

Spray the moulds with Mann Ease Release 200. I actually cut slits down either side of the moulds to allow me access into all the nooks and crevices, and to aid in removing the final cast. Build another well as before. Mix and pour your silicone.

Again, wait the allocated time, remove the wrapping, and demould your ears. They should come out quite easily.

The clear one is the platinum, the blue is the interim failed experiment with tin silicone. Congratulations Dr Frankenstein, you’ve finished the hardest part.

Next: Ear canals, mounting ears, building a base and finishing up