A boat builder on DuckWorks posted this:
"... For lightweight glass, less than 4 oz, just use it to fill the weave and add an additional coat. For heavier glass, fill the weave with a microballoon slurry (to keep the weight down), then put on a couple of coats of the graphite/epoxy mix.
I've been doing this for years on multiple boats. I've found that this combination works more effectively against oyster shells and gravel than plain epoxy, but no better against concrete and sand. The nice thing is that the contrast between the black epoxy/graphite and the wood (or microballoons) lets you know exactly when & where the renewal is needed.
Laszlo"
"... For lightweight glass, less than 4 oz, just use it to fill the weave and add an additional coat. For heavier glass, fill the weave with a microballoon slurry (to keep the weight down), then put on a couple of coats of the graphite/epoxy mix.
I've been doing this for years on multiple boats. I've found that this combination works more effectively against oyster shells and gravel than plain epoxy, but no better against concrete and sand. The nice thing is that the contrast between the black epoxy/graphite and the wood (or microballoons) lets you know exactly when & where the renewal is needed.
Laszlo"