This will work. The molded part is on the left and lightly sanded to remove flashing. After polishing it should look very good.
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When I flipped the mold, there was a bit of air in the mold.
Since the mold is sealing well, I'm going to mold a straw into the next mold and pour from the back and just tilt the mold to make sure that it the high point. I'll have little nub to sand off, but otherwise it should be perfect at that point.
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That bubble is probably not from air being trapped but rather a carbon dioxide bubble that formed from atmospheric humidity reacting with the resin though could just be a trapped bubble. Normally casting like this is done in a pressure pot at 60psi though and the only thing you degass is the rubber for the mold, not the resin you're filling it with.
I work at a special effects company these days but also made silicone molds and parts for years before that. Not sure what pigment you're using (you're calling it dye so even less sure) but I highly recommend a product made by SmoothOn called UVO. It's a UV stabilized pigment that's super easy to use and can make fully opaque parts.
I think I saw you're using epoxy but that's a not an ideal resin for this, between shrinkage and its brittle nature. A urethane like Task9 (low shrinkage and very tough) by SmoothOn https://www.smooth-on.com/products/task-9/ or Innovative Polymers equivelant IE3075 http://innovative-polymers.com/images/specs/Classic-Shore-D/IE-3075.pdf would be better.
If you want to maintain precise dimensional control and reduce your finishing process use a 2 piece mold that bottom fills and has risers, this way you only need to cut a few sprues and deal with a few nubs and have professional looking parts. Here's a little album I put together making a mold of a trigger for the left hand Warthog grips I used to sell, demonstrating using Lego for mold walls and how to make a bottom fill mold with a vented riser
Here's a pressure pot I made for casting out of a pressure pot for painting, which also has a heating element built into it as I was producing year round and needed to control the temp as well as a built in moisture filter which has since been replaced by more traditional desiccant
Also, silicone molds will only last for like 20-40 pulls before it starts getting too tired to yield good parts so you want to take molds of your mold so you can make new production molds as they age if you plan on doing this for any length of time. Lastly, while silicone has natural release properties, it also degrades over time and you need to use some kind of mold release. Mann200 is my preferred product for this. https://www.mann-release.com/products/ease-release/200/#