[...] it required 2% catalyst, I had tried 5% and 10% but it didn't work. I still don't know why? maybe it's coming from the mixing process 
Oh, don't do that.
The silicone itself is usually body-neutral, while the catalyst is often a carcinogenous, liver-destroying kidney-wrecking compound of metal salts. Most of it gets trapped inside the silicone if you observe the mixing ratios. When you add more of it, then, well, it doesn't. It also changes the properties of the silicone. If you're gonna use or sell caps made with that mix, they're gonna have this stuff trapped in their surface, coming into contact with people's fingers for prolonged amounts of time.
In the manual of the silicone you're using, it should be written what kinds of substances inhibit the setting process. Like sulfur, or rubber.
Read that, and make sure none of them are present in your model, on your hands, gloves, or in the mixing process.
Don't throw away your mixing cup with silicone residue, keep it as a setting test. For a few weeks, preferably - bad mixing (or too little catalyst) will eventually set, while contamination won't.
Mix for a few minutes at least. Try different containers and mixing sticks. If you're using platinum-based silicone, it's safe for handling, but very sensitive to contamination. It won't set in minimal presence of certain chemicals (like sulfur).
But whatever you do, try not to mess with the ratios, unless you've got specific info about that in the silicone's technical sheet, or have contacted the manufacturer.
