In my experience, dirty glass cloth is a bummer worth avoiding, not to mention any runs and snags which have probably occurred. Even small amounts of dust will create a nubbly, rough surface which will cost you alot more sanding than you want to do. Chunks that extend through the cloth could create wicks that would allow water to get underneath the layer. Invisible oil or wax spots that may be lurking there could ruin a whole layup. When you consider that nice, clean, new glass is only $3-$5 a yard, it hardly seems worth it to jeopardize a project which may ultimately be worth thousands. Now, if it is just the outside of the roll that got dirty, and if it has stayed dry, I wouldn'hesitate to just cut off the dirty part and use the rest.

: I have gotten access to a roll of fiberglass cloth that was left out in a
: shop for many weeks. It had been subject to general dust and airborn
: sawdust from wood working projects. Other than shaking it out well, should
: I do anything to further clean it? Will the epoxy still saturate and
: adhere well enough without special treatment or handling?

: Thanks, Randy