A simple and very cheap way to make custom shaped moulds for creating simple resin castings with or without an LED embedded into them.
The mould is based on a popular technique on the Internet which uses common household materials to make good silicone rubber moulds. It’s basically just standard sealant silicone mixed with cornflour (cornstarch) to make a malleable putty into which your master shape is pressed. If using non plastic masters then apply some oil or Vaseline to the object so that the silicone doesn’t stick to it.
When the mould has cured in an hour or so (but leave overnight if possible) then the master can be removed and the flexible mould can then be used to produce replicas from various resins. I like the simplicity of the two part syringe resins which can be bought at dollar store type shops.
To embed an LED I prefer to use the shorter “strawhat” 4.8mm LEDs as it helps to keep the chip as far back from the front of the casting as possible for good light distribution. Bend the leads to the side at right angles to the LED so that it can be placed across the top of the mould with the LED submerged in the resin.