Epoxy for sealing timber

[seanfoster]

Further to a previous thread, I want to seal some ply to prevent moisture.

The replies I had mentioned coating in epoxy and then varnishing afterwards.

Could someone expand on this?
What epoxy should I use (I've never used it before so could do with some tips), how do you apply, I assume a polyurethane varnish over it?

Any help would be appreciated!

 

[prv]

I believe you can get special extra-runny soaky-in epoxy for the purpose, but you'd probably be fine with normal general-purpose resin. They make the basic stuff thinnish, then if you want glue or filler or fairing mix you add various proportions of powders yourself - so with none of that added it would be fine for coating I'd have thought. Certainly I brushed a coat onto a plywood stowage box I wanted to keep in the bilge and it worked fine - came out like a very matt varnish. If I cared about its appearance I expect some actual varnish would then render it shiny.

I habitually buy West epoxy, but I doubt there's much to choose between the big names.

Pete

 

[electrosys]

West Epoxy is completely unsuitable for sealing plywood, as it's too darned thick (viscous). Indeed, I cannot understand the ongoing enthusiasm for this brand - good marketing I guess.

Some people will say that it can be thinned with acetone or cellulose (lacquer) thinners and, whilst that might be true, when the solvent evaporates, it will leave behind micropores which will then allow moisture to penetrate, which kinda defeats the whole purpose of sealing.

Better by far to start off by using a thin epoxy, such as Epiglass, or my favourite, General Purpose Lay-Up Resin from ABL Stevens (www.resin-supplies.co.uk). As a bonus, the GP Resin has a much more user-friendly 2:1 mix ratio, than that of West 'Systems'.

I will not even allow West products to enter my yard, precisely because of it's unsuitability for boat-building.

(just putting my flak-jacket on ...)


BTW - ABL Stevens supply a UV-stabilised epoxy for the final coat. Can't comment further as I've never used it. I prefer good old paint.

 

[gjgm]

West epoxy is too thick? What temp are you trying to use it at then, coz its pretty runny when I use it.
Note there is no UV protection in epoxy, hence the need to varnish afterwards.

 

[Tranona]

Really is unnecessary to coat ply unless it is for external use or you want to increase stiffness without increasing weight and thickness. It is a waste of time and money for internal work. The weak area in ply is the end grain and there is value in soaking this in epoxy. You can dilute West with their own dilutant if it is too viscous. An alternative (the pre epoxy way) to protect end grain and that is cap it with solid wood using either epoxy or a polyurethane glue such as Balcotan.

The face of ply can be finished in any of your chosen bright finishes - personally I use Ronseal satin internally and Sikkens externally. Epoxy has its place externally, but is not generally UV resistant so is better painted or finished with a UV inhibited bright finish

 

[Poignard]

Epoxy use comes up quite often on the Wooden Boat Magazine Forum.

http://forum.woodenboat.com/showthread.php?117487-Mystery-with-clear-coating-eoxy&highlight=cpes

A search on there might get you some helpful information; which is not to say you won't get it here but I think there are many more wooden boats owners in the USA so there's a greater collective experience.

 

[ianj99]

Further to a previous thread, I want to seal some ply to prevent moisture.

The replies I had mentioned coating in epoxy and then varnishing afterwards.

Could someone expand on this?
What epoxy should I use (I've never used it before so could do with some tips), how do you apply, I assume a polyurethane varnish over it?

Any help would be appreciated!

Epifanes Epoxy Primer - states on the tin, 'can be used as a woodprimer on non-working wood. '
Its not very viscous so should penetrate well but can be thinned upto 50%.

Also suitable for use as an anticorrosion primer on steel and aluminium and as a filling primer on grp prior to applying polyurethane coating.
I

 

[seanfoster]

Thanks for the replies, that's given me something good to go on.