The problem with silica is that it takes on taste very easily (that's also the good thing of course) when wicking so handle it as little as you can and burn the shit out of it. I'm talking about holding it with tweazers and nuking the stuff over a cooker. That said, I don't bother much now other than a quick 'dry burn' before use as I know how it works.
If you don't burn it you'll sometimes get about 1/2 ml of shite flavour before it rights itself. That's why some new 'builders' say the juice is shite, when in fact it isn't, it's just that the wick was handled with greasy hands for 10 minutes before use.