Almost all of the fabrics are good for epoxy resins. Some are finished for just polyester, some just epoxy and some are good for any resins. A little background on finishes. Finishes are put on glass fabrics to allow a strong bond between the resin and the glass. If you take a sheet of glass and put resin on it, let it cure then try to peel it off it will easily come off, or chip off. Finishes like Volan or Silane act as intermediaries between the resin and the glass. Volan has been around a lot longer than the Silanes but I think is still one of the best finishes. Volan is generally the softest finish with the exception of some Silanes. Volan is a chrome based finish that complexes with the silicon dioxide in the glass and leaves one group to bond to the resin. Silane is a molecule that, like carbon, has four groups (bonds) with three of them bonding to the silicon dioxide in the glass leaving one group to bond to the resin. Some of the reasons for using Silanes instead of Volan are:

• Doesn't leave a green tint like Volan which is preferable for surfboards.

• Forms a little stronger bond and generally considered more moisture resistant.

• Better for the environment.

When cloth is woven it has an oily starch type material on it to make the glass yarn slide a little easier to prevent breakage. After weaving is complete the cloth is heat cleaned to remove any of this material then the finish is added. There's a lot to know about Finishes and you want to be sure you're getting cloth that is proper for the resin and application you're doing.

The thread count and weave of the fabric can make a lot of difference in the the handling of the cloth as well. Some weaves are tighter than others and are not suitable for complex curves. The satin weaves will take complex curves better but are a little tougher getting the bubbles out. Satin weaves are also effected by the type of finish. This is probably because the yarn is closer together and allows cross bonding of the finish more than in plain weaves. For example, there's a tremendous difference in the way a satin weave like 7781 will be if it's finish in Volan or in a Silane. Some Silanes are pretty good while some can be pretty stiff and good for flat panels only. We sell the stiffer material for a good bit less than the softer material. Unidirectional fabrics are for composites where you need the strength in one direction like in a wing. Or, you need it to conform in one direction more as would be the case for composites tubes. Some of the unidirectional fiberglass styles include 1557, 1543, 3743, 7715, 7721 and 2515.

You can get some idea by the count - threads per inch. Warp is length wise down the cloth and fill is side to side. If you laid a ruler on the cloth and counted the threads in one inch that's the number you'd get.

The lighter weight fabrics like 106, 6060, 1080, 112, 2113 are the ones that have been used in model planes for years, with 106 being the most common to use with epoxy over balsa skins. For molding R/C fuselages softer materials like 1522 3.7 oz, 7533 6 oz type materials are easier to use than tighter weaves.

A lot of the fabrics were first used primarily in the circuit board industry and because of this more is available at cheaper prices. Some materials that are easier to laminate are more expensive because of the higher demand and lower production.

S-2 glass - Most of the materials on this site are E-glass with the exception of styles like 6116, 1893, 4526, 6781, and 17645 which are S-2 glass and are noted accordingly. S glass (primarily S-2 glass) is generally considered to be about 20% stronger than e-glass. S-Glass is 64-66% Silicone Dioxide compare to E-Glass at 52-56%. S-Glass has no Calcium Oxide where E-glass has 16-25%. S-Glass has more Aluminum Oxide at 24-26% where E-Glass is 12-16%. S-Glass has no Boron where E-glass is 5-10%. S-Glass does have 9-11% Magnesium Oxide where E-glass very little. The price of S-Glass is higher than E-Glass. The reason for this that was given to me some years back is that S-Glass is processed at a higher temperature than E-glass. It burns through the oven liners faster and this replacement cost is the reason for the higher price.