Tom and Lisa's Weird Web Page

Following some information from this page

http://www.powerbook.org/duo-zone-e/danger/clear-parts.html

(which by the way is a great page, but a little unclear in some parts) I decided it would be pretty spiffy if I could make colored parts for my Duos.  Mind you, I don't think this technique can be used for large parts; which would require a professional ($$$) job.

From the above page I collected the various implements of this project:

- Silicone monomer (TinSil 70-25 from www.sculpt.com)
- hardening catalyst (came with the above)
- a package of oil clay (xxx)
- release agent (petroleum jelly in mineral spirits)
- resin epoxy or polyester monomer (part # from www.eti-usa.com)
- hardening catalyst (part #xxxx from www.eti-usa.com)
- set of three coloring agents (part #xxxx from www.eti-usa.com)
- some cups, wooden stirrers, brushes, tape, measuring cups and other miscellany
- a small scale that has 1 gram resolution (OK, I _wish_ I had one)
 

Following the general instructions from the above link, I made a small cardboard box with no top or bottom. Using the oil clay, I made a small bottom for the cardboard box, taking care to firmly seat the box into the clay, to prevent leakage of the silicone.

Now, I took an original duo trackball and trackball ring, and pressed each of them into the clay surface, so that each one was about half way into the clay.

Then, I mixed a batch of the tinsil 70-25 silicone, following instructions.  After thoroughly mixing the silicone, the material had a pale sky-blue color.
 

Then, taking care to slowly pour the silicone as to not force a lot of air into the mixture, cover all the parts and have at least 1/4" of silicone liquid over the tallest part.

This is what it looks like after pouring:

Now, you wont be able to avoid getting bubbles on the surface of the silicone altogether, just try to be careful.

Let the silicone cure for at least 2 days (3 is probably good enough), before removing the box (careful - don't destroy the box, you need it later).

After removing the box, and removing the clay base, this is what I saw:

Now, turn the mold (with the parts still in it) and put it back in the box you built earlier.  The plastic parts should be facing up. If you poured the silicone over the parts now, you would create a nice mold with one problem - there would be no way to inject the epoxy plastic !
You need to add a small round dowel part (or use a piece of clay) that runs from the plastic piece to the edge of the mold.  This will create a channel that you can use to inject the epoxy later.  I suggest making 2 channels per object to allow an easier escape for air.

Now, we need to make sure the new silicone we are going to pour does not bind to the first block of silicone.  I bought some release spray (Pol_Ease 2300), but it was not the correct type to use.  Fortunately, the instructions that came with the silicone itself suggested using a 10 weight% solution of petroleum jelly in mineral spirits. I just tossed a large chunk of jelly into about 75 mL of mineral spirits and stirred it up good until I made a homogenous looking suspension.

Using a small paint brush, brush a light coating of this mixture on top of all surfaces that will contact the new silicone layer you will be adding.  Let most of the mineral spirits evaporate off; this should make the surfaces you coated slightly slick.

Once again, mix some of the silicone material together and pour over the top of the first silicone block and plastic parts, making sure there is enough silicone to cover all the parts and leave a1/4" later or so over the top.  Let dry for 2-3 days and take the cardboard box off.

Before taking the molds apart, use a pen to mark how the 2 blocks fit together.  Now, carefully, separate the silicone blocks, taking care not to tear the silicone. If it worked well, take the plastic parts out carefully. You should see a clean molding for the parts as well as 2 channels for each part.

Carefully put the 2 silicone blocks back together.  Wrap the blocks with rubber bands to tightly hold them together. Try not to tear the silicone rubber.
When the blocks are firmly together, you are ready to make and pour the epoxy.

Before you actually start this, you should know that it is likely you might have to experiment with different combinations of resin and hardener and colors to find what works.

I also suggest figuring out the approximate volume of the pieces you are molding so when you inject the epoxy you know about how much you will need to make.

For my first attempt, I used 15 mL of resin, 1 drop of blue color, and 1 drop of hardener.  Mix thoroughly.  Wait a few minutes to allow the air bubbles to leave the resin mixture. The ideal way to get this resin into the mold, in my opinion, is to use a syringe to inject it into one of the channels.
Slowly inject the resin into one of the channels until resin starts to come out of the other channel.  After doing this, I also put the mold into a water tight bag and submerged the bag into a bucket of water; this allows water pressure to insure a tight seal.

After 4 days, I took the mold apart, and this is what I had:

Not a success; the items didn't have enough epoxy (I forgot to add enough) and were still somewhat tacky, indicating I did not add enough hardener.
Such is life.

My next batch of epoxy.........