Whoever said that there is no such thing as a stupid question is wrong…but I need to ask this one. Is 3.7oz glass the same as 4oz glass, or are they really 0.3oz different? If they are the same, why does FiberglassSupply have to be difficult and make my head hurt so much?! I searched and gave up, so sorry if this has been covered 800 times before.
–BCo
same
glass weights may vary a bit between manufacturers. some are 3.7…some are 3.9…none are 4.0…but it’s ALL “4-oz glass”
It’s just a round-off to “4 oz”. “6 oz” is usually an actual 5.7, etc.
I’ve never understood why we haven’t been more specific about cloth
weights in this industry.
If you’re ordering and ask for 4 oz, they’re going to tell you they don’t
have any. They do have something close, so don’t get a headache.
I once told a customer he was getting 3.7 oz cloth on the bottom
of his board and he looked at me like I was ripping him off for that
.3 oz…
Mike
Yeah even the makers of the glass round off the weight.
For instance here is BGFs brochure: http://www.bgf.com/SiteSearch/Brochure/prodReinAerialite.pdf
And here is the real technical data: http://www.bgf.com/TechnicalChart.asp?CategoryID=19
If you really want to know make sure you ask your supplier for the “style number” and the “maker”, since different makers will do the same style fabric, using that same style number. And then you can probably get detailed info off the web.
Also different makers of the same style might use a slightly different “finish”.
Glenn, Mike, and soulstice,
Excellent answers. I figured that was probably the case, but wanted to make sure.
Soulstice,
Well put. They all make 4oz, but none of them is 4oz. Got it.
Mike,
Funny that your customer thought you were ripping him off. I guess for 4 oz glass, it is almost a 10% difference in weight, but your customer’s reaction is still funny.
Glenn,
When you say finish, do you mean in terms of the coating on the glass (e.g. volan)?
–Ben
The metric system translates to funny numbers in ounces… 
Much more accurate though! he he
I use 25 gram, 50 gram, 76 gram, 100 gram, 125, 130, 195, 210, and on and on…
100 gram is pretty much 3 ounce, and the 76 is about 2.2 ish, thats what I use most of!
Definitely get a sample of any new cloth and test it on a scrap of white foam, for clarity.
And check the thread count - not many people mention it but it important I feel.
The thread count contributes to things like crimp, which have a large influence of the properties if the cloth.
In the archives there is a lot of info written by some of the pro guys who know more than is healthy about cloth!
Me, i’m on a cloth diet.
Kit
Glenn,When you say finish, do you mean in terms of the coating on the glass (e.g. volan)?
Yes. What I’ve found is that if I put the “finish number” with the word “finish” in at Google you can often times get the answers you need on that as well. Looking at that tech link above the finish is A218