Sunday, August 7, 2011

The Mold: Rubber Shell

Here, I am at TechShop --it a bench of course-- setting up the clay retaining walls for my mold... I used modeling clay from Chavant Inc., it has a good amount of "stick" yet remains solid for forming ( I used the sulfer free blend, of course). I love this clay a lot, gotta get more.

After the first layer, I add more clay... this time, I'll try a shallow vertical wall to better retain the bottom edge and maybe form a lip to help hold the hard outer shell I'll later add.

Next, with the wall in place, I mix up some fast curing Smooth-On™ Oomoo 25 (75 minutes!) as there is a lot of it around TechShop for my class.

I use fairly old, on the shelf (used, open bottle--etc) Smooth-On™ Oomoo 25 as it tends to go off faster (thus making it a little unpredictable for class), this will allow me to form a nice "globby" coat for the first layer detail coat, yet still be pourable-ish to flow where needed.

 Sometime later (about two hours), I can do the next layer of Smooth-On™ Oomoo 25 after some . This layer was a bit "newer" batch, so I just waited for it to start gelling before I spread it out over the part...

... this layer was "hand smoothed" as it cured, so more of the material ended up on top of the job. This a tedious way of doing things, but I had none of my trusty Cab-o-sil on hand for thickening the layer. Cab-o-sil is great for adding, by degree, a lightweight thickener.

Curing now, I'll post more as I do more :)

Next: The Hard Outer Shell!

© Tom Twohy 2011


  1. Lydia want me to buy some pewter sheet for my metal spinning so that she can use the scrap for casting pewter using the Smooth-On product you told here about. She has been talking about rubber mold for days.

  2. How about, "Metal Parts from Rubber Molds!" This seems like a good headline for a post. I did't understand the significance of this until just a few days ago. I know you have been talking about it for over a year now, but who listens to an "artist" anyway!