Blackout material

I found some blackout material made by Rockland Industries that is sold thru drapery stores. It is thin, flexible, and a fraction of the cost of other material I have seen offered for photographic use. It is white on each side.

I haven't made anything with it yet but I wrapped a piece around a 500W quartz-halogen light fixture and it totally blacked out the room!

I'll be trying it for a bellows soon and will use it to replace my black blackout cloth (which is HOT in the sun!). I'm also going to replace the fixed shutters in my darkroom with removeable cloth curtains from this material.

http://www.roc-lon.com/Blackout_FAQ.htm

What will you use for the inside of your bellows? I think that having white inside would be a bad idea, as stray light bouncing around the bellows is sure to reduce the contrast of your pictures. I'm interested in your thoughts, as I need to make up some bellows soon.

Thanks in advance.