Resin question

Hello
I’m restoring a Stowe osprey and while adding the fiberglass foot ball to the bottom i found I could not get the glass to go clear. I’ve glasses lots of boats and this was new to me. The resin was west system and the mat was .75 ounce. With resin applied the cloth turned clear in some places and morsel milky white. I ended up pulling up the wet cloth and scrapping it. Any idea what caused this (and how to avoid it on the second go around)?
Thanks
Jamus

 

Fiberglass cloth and fiberglass mat are two very different things and you are using both terms to describe whatever it was that you were using. If it actually was 3/4 ounce mat, be aware that it really is not compatible with epoxy resin. It is made from chopped short (non-woven) strands, glued together with a binder which will dissolve when saturated with polyester resin (not epoxy resin). Once it dissolves, it allows the mat to conform to odd shapes and contours. It adds stiffness, but not much strength and also tends to add a fair bit of weight because it soaks up so much resin.

Another potential problem, which can happen with either fiberglass cloth or mat, is that resin (any type) doesn't naturally stick all that well to glass fibers. To remedy this, the fiberglass is treated with a sizing (volan, silane, etc.) which allows the resin to saturate it and bond properly. Most of these sizings are actually water soluble. If your fabric or mat has been allowed to get damp in spots or really humid, you can have areas which don't fully saturate properly and will stay white-ish in color. Other chemical, oil and solvent exposures can do the same thing, so always know where your fabric has been and keep it pristine - even to the point where you should be wearing gloves to handle it to prevent oil transfer from your hands. Learning to work clean and contaminate-free is a big part of learning how to fiberglass properly, and there are an awful lot of lousy home fiberglassing jobs out there.

 

Hi Todd
Very helpful and thank you. I was indeed using mat (chopped) and the fabric was new and unopened so I suspect the issue that I encountered was due to incompatibility with epoxy. I have built a few stitches and glue boats and have not encountered this issue before so it was a head scratcher. I appreciate the time and response to help clarify. I’ll sand out all evidence of the first attempt and have at it again with poly resin. Thanks
Jamus