Reply by CaptainKlutz

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Posted on Table Top Butcher's Block Oil

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602 posts in 1697 days

#1 posted 01-30-2018 01:34 AM

Reads like you between a rock and hard place. :(

Famowood epoxy coating is intended to be a thick protecting top coat. About only surface coating used on clear epoxy coatings is wax and then buffing it out to achieve the desired sheen.

Worse – Not many finishes are going to stick to epoxy coated surface, unless it is roughened to create a mechanical bound. The level of roughness required (~80-100 grit sand paper) will not work under a regular (varnish/poly) clear finish as the sanding scratches will be visible.

If epoxy coating is still sticky, then as others stated: either the mix ratio was wrong, or cure temp was too low.

Epoxy has minimum cure temp requirements (usually >65F). If you attempted to cure at low temperature, then a bad thing can happen = the long cure time will allow epoxy to surface blush or out gas some of the curative that is not reacted fast enough. This creates a sticky film on surface, and if temp was low enough will prevent proper cure/hardness of the epoxy film.

There are not many options to correct this problem:
First, place the item in hot location >85F for 72 hours, or >100F for 48 hours. Slow cure epoxy systems can take 2-4 weeks to fully cure at room temp (72F), so you need significant heat to accelerate the process.
Second, you can attempt to sand the surface with 220/320 grit to remove the sticky film, and determine if epoxy is cured hard enough to be used. If the top can be dented with fingernail after extended high temp cure, then the epoxy is not fully cured. Only solution is to sand off the partially cured epoxy, and try again. If the epoxy has hard surface then you can continue to sand with 400/600, then buff with wax to final sheen.

Other epoxy tips:
You can make repairs to a the clear epoxy finish, but they are very hard to hide. The challenge is edge of the top coated epoxy (due surface tension). To repair, sand area to be re-coated with 150 grit, clean dust/grime with fast dry solvent (alcohol is safest, MEK – acetone clean better as long as not allow to soak on surface). The re-coat with more epoxy.

Have not used Famowood brand, but most epoxies can be diluted 5-10% with denatured alcohol to lower viscosity/repair thickness, which will reduce height of edge. This can reduce the need to blend/buff the edge to hide it. Note – ambient temp needs be high enough to allow the alcohol to evaporate before cure, so thinned epoxy application works best 75-85F working temp. It is always a good idea to test your thinned epoxy mixture on extra board, and give it a complete cure before committing to a finished project. If alcohol is not fully evaporated, end up with softer epoxy.

Instructions for epoxy always suggest mixing in small qty. That said, you can safely mix 1 gt (or more) at time, providing you follow some basic cautions. This larger epoxy mass will exotherm and begin the curing process much faster; So you must mix it quickly (but thoroughly), and then reduce the mass per unit area quickly.
Common trick is to use a small drill attached mixing blade (slow speed to minimize bubbles), and then pour the entire contents out onto your surface so that self heating is not carried into entire mass of epoxy. After pouring out, typically use a squeegee/large putty knife to spread coating on the surface to slow the cure rate and allow normal working time to “level” the surface. If you feel the container getting warm during mixing, that is your indicator that time is rapidly running out. Need to dump it out quick on the table top and start spreading. Uncured epoxy on mixer cleans up easily with acetone.

Best Luck.

-- I'm an engineer not a woodworker, but I can randomly find useful tools and furniture inside a pile of lumber!

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