Silicon degassing with negative pressure

I am planning to use polydimethylsiloxane (PDMS) to create phantom for mimicking tissue for imaging. For this, I plan on using [SYLGARD® 184](http://www.sigmaaldrich.com/catalog/product/aldrich/761036?lang=en&region=US), which is a viscous liquid. When adding other components to it, the air bubbles will be introduced. I have learned that one way (available to me) is using the negative pressure/ vacuum pump to remove bubbles / de-gas the solution. Does any one knows what negative pressure is sufficient to remove the air from the gel-like solution?


