Hi All-

I got a response from Tom Pawlak at Gougeon Brothers, and here's what he said:

"We have not compared abrasion resistance of epoxy modified with 423 Graphite Powder and 420 Aluminum Powder but I'm quite sure 420 Aluminum added to epoxy would be more resistant. Graphite powder is not very strong (it is the equivalent of ground pencil lead). I believe its popularity as a coating for small boat bottoms is mostly based on urban legend rather than side by side tests. You can add as much 420 Aluminum Powder as you like (easily 3-4 rounded tablespoons per 8-10 oz. batches of epoxy) as long as you can still roll it out and brush it smooth. The more you add, the better it would resist scratching but eventually adding too much would impede getting a flowable epoxy coating."

I asked for some clarification in regards to weight and silica, but I'm restoring a squirt boat, so abrasion resistance is important since it will absolutely be run over rocks. Since It's more resistant I can probably put less on, so that will help with weight, or at least equalize it. I'll give it a try and let you know. I had my heart set on a black bottom, so I may experiment with adding some black colorant to the epoxy. Might give me a metallic look.

I will post additional information as it comes along.

m