Heat resistant silicone mold

Source: https://www.youmagine.com/designs/heat-resistant-silicone-mold

Description: The old seal of our oven was not really resistant to heat and chemicals, so we decided to replace them with silicone seals. The results are not perfect (visually), but may be improved. Anyway, they are fully functional. Before filling the mold with heat resistant silicone, I spread vegetable oil inside the mold with a brush. I think while I was filling the mold, the oil mixed with the silicone, so I couldn't pull apart the cured silicone. Then I decided to melt the mold in a 220C oven. It worked, but stains of PLA remained on the silicone parts. To get rid of the PLA, I put them in warm sodium hydroxide solution (60-80C). The solution removes PLA, but very slowly. After 5-6 hours I got bored and decided to use them as they are.So, there are two problems I encountered: 1) I could not remove the PLA easily.2) There are voids inside the silicone parts.To solve 1, I need to find a better method to separate silicone from mold. If I can, the mold will be reusable. I am considering spreading molten margarine then freezing the margarine by putting the mold in a fridge. After curing, I will put the mold in warm water.To solve 2, I will need a vacuum pump.