If your objective is to create a silicone product, take a different viewpoint of your research thus far. Silicone molds work because silicone sticks to almost nothing other than silicone. If you create a mold using silicone as the foundation, pouring food materials inside means you get food materials out, without sticking.
For your beads, consider that you want a non-silicone mold. The hole in the center makes things a bit trickier, but not by much. You'd have to make a two-part mold and ensure that you get proper venting when placing the sprue for filling. Alternatively, if you don't mind a seam in the finished product, you can make two molds that can be filled independently.
You didn't state the diameter of the beads, and I'll adjust this suggestion to focus on small sized beads, as the project gets easier with increased size.
One will presume that you have ordinary beads of the size you wish to duplicate. The typical method of creating a non-silicone mold requires that the item be coated with a mold-release substance. Tiny beads are likely to be very challenging in that respect and you cannot expect one hundred percent perfection, in my opinion.
A somewhat step-by-step method would be as follows:
- Create a modeling clay base, leveled as carefully as possible.
- Embed the beads in the base to the half-way point, ensuring that the orientation of the through-hole is vertical.
- Embed also in the base at various locations across the bed alignment points. These points can be clay-formed bumps, pyramids, cones, something tapered for easy release. Tapered depressions will also serve well.
- Coat the beads and the clay surface with mold-release.
- Encase the clay bed within an appropriate box-like structure to create a pouring frame.
- Select a desired resin and fill to cover the beads and alignment points.
- When cured, remove the clay bed but leave in place or clean and replace the beads.
- Clean and apply mold release to the cured mold and the beads.
- Create a new pouring frame around the cured mold.
- Pour the second half of the mold, allow to cure as before.
When the mold are split and cleaned, any silicone compound applied will form the beads. Without cutting a sprue or vent, you can fill one mold flush with silicone, allow it to cure. Do not touch the cured surface. Fill the other half of the mold with silicone and place the first half in place atop it.
The uncured silicone will bond with the previous pour and create the beads. Depending on the amount of silicone used, there may be thicker seams.
I do not believe small beads can be created using molds involving a sprue and vent. Because the spherical shape of a bead requires a two part mold to release the bead, it is more practical to consider the seam-style creation.
The tricky part will involve ensuring the clay bed fills the bead opening when pressing them in place in the earlier steps. Cleaning the clay from those openings when creating the second mold is equally important. Any points of failure in those items will create a bead without a pass-through hole.