Silk Screening Question

[frank-lynk.livejournal.com]

I've recently got into silk screening on to T-shirts

I'm using SpeedBall Fabric Paint.

I find that when I use white paint on black shirts, the paint doesn't come out very bright.

It kindof has a "grey" look to it.

anyone have suggestions on "darkening up"  white paint so that it actually looks white??

any advice would be greatly appreciated.