How do you know if your fiberglass is what it's claimed to be?

I've ordered about 5 rolls of various glasses from 3 different sources. One source's 12oz woven is heavier/thicker than another source's 18'z biaxial. Now I know they aren't apples to apples (I ordered different fabric from each), but also the 12oz is way heavier than the 10oz from another source. I'm thinking the 12oz I ordered is really more like 18-22oz fabric that was mislabeled?

Anyway, other than just knowing by having enough experience, is there a good way to identify fiberglass fabric other than cutting a square yard and weighing it? I don't have a scale that will accurately identify 10 v 12 oz fabric.

 

Did you read this post?
http://www.boatdesign.net/forums/all-things-boats-and-boating/side-effects-crisis-42635.html

You don't need to cut of a square yard. Use a kitchen scale or even one for letters and a smaller piece of glass, then calculate surface times weight.

 

Thanks CDK. Unfortunately I don't have an accurate scale. I can probably find one though. The one fabric that seems way off on weight and thickness was from a chinese supplier. I suspect they just shipped a roll of "something" that kinda looked like fiberglass fabric. I only bought 50yds, so I'm not out much $, but I'm not going to use it on my boat.

 

I have found with glass that the supplier is the key. Fiberglass Supply in WA state is pretty good with quality products.

I ordered mine directly from the manufacturer in the southeast USA, but that's because I ordered 18 rolls of 34oz and miles of tape.