>I got confused with the sand,
>the silver silica sand made
>me think it was a
>different product altogether, how long
>would it take for the
>silica to fall off?

I do not know how fast it will happen. It depends on many things for one - how much of the mica is in it?
Also silica sand might have been quarried by the sea, therefore contain salts and salts are the biggest enemy of fresco. (I am not sure about the last one, but the first one is good enough for me)

Getting revere sand should not be a problem - you do not have to go to the river bank and dig it out. Masonry supply store will tell you where the sand came from, you can use "play sand" it should be river sand and also it comes pre-washed.

>One more question can fresco be
>carried out on plaster board,if
>thats the right name for
>it?

Do you mean "drywall" and what do you want to use it for? As a backing for the fresco plaster coats? I think Gary's system is simple and right and for the small (1-2 sq. feet) panel it is pointless to use any other method. Gary is an expert in "stucco duro" and other plasters.
Just use very little of white cement, and I would not put it into intonaco.

Ilia
http://www.truefresco.com/workshop