Softer silicone for mold - any impact on accuracy?

The dimensional accuracy largely depends on the hardness of the silicone used to cast the mold. Softer silicones tend to flex more, which can lead to greater deviations during casting, especially with tight tolerances. If precision is critical, you might want to experiment with only slightly softer silicone—something that compromises flexibility and stability.

Absolutely. Softer silicone won’t hold a polished finish as well as harder variants. If your prototypes require a high-gloss or polished surface, it’s better to stick with a firmer silicone and accept the difficulties in demolding. For functional parts, though, this may not be significant. Testing a couple of options will help you dial in the best fit for your specific needs, but you might need to be ready to iterate the tool