I build have been building picnic tables out of SPF for the table tops and bench seats. I use pressure treated for the supports and legs. My problem is the finish on the top and seats. After a year some of them start peeling/flaking in spots. Nothing major just in spots. I live in Michigan so the tables set outside all year mostly unprotected. In my process, I run the boards through the planer and do some light sanding first. Then stain them, let them dry, and apply 3 coats of “Minwax¯ Helmsman¯ Spar Urethane ” semi-gloss poly (oil based) on all sides. Am I fogetting a step? Should I use a sanding sealer first? My thinking is that the finish should last least two years. Your comments and suggestions are welcomed. (I do not poly the pressure treated, just stain those).
Thank you for taking the time to read my question.
Len
Replies
save your self a headache...leave them unfinished.
I cannot answer the main thrust of your question, but I can answer to the sanding sealer. Sanding sealers are used in order to get some quick build without having to wait for longer curing finishes to harden. This is often done if you want to fill the pores or get a level surface without waiting long before sanding.
Sanding sealers will not improve the adhesion of polyurethane based varnish. In fact, many (if not most) poly's do not adhere well over many sanding sealers. Traditional alkyd varnish will adhere well over many sealers such as shellac or lacquer based.
De-waxed shellac can be an acceptable sealer under polyurethane based varnish.
But again, the lack of a sealer is not your problem here. They are only for shortening the finishing time and sometimes for providing a barrier between incompatable surfaces.
As for the failures you are experiencing, you will be better served listening to someone that has had success with exterior finishing.
Len
I am not an expert on this, but have learned the hard way that spar varnish is not durable for this purpose. It is designed to be soft and resilient, not hard. I have a ash park bench that I finished with spar varnish, and the finish wore off in one month, where you sit. Everywhere else, it had been penetrated by water. You could peel it off with a fingeranil. I don't think it was my preparation, just not the purpose for spar varnish. I wouldn't use anything, but if you must, I would look into the deck-type finishes, not a furniture finish.
I wouldn't use anything, but if you must, I would look into the deck-type finishes, not a furniture finish.
exactly. I might add NOT Thompsons.
Cuprinol, olympic clear, log house finish etc.
Go Stab yourself Ya Putz! Ya think I Parked here?
Len,
I've built picnic tables for about 27 years now. Yikes, I'm getting old! Anyway, the best finishes I've found are, in no particular order:
No finish.
Krylon polyurethane (tinted- brushes on like an oil paint, very durable),
and a product called Man O' War which seems like a tinted poly too.
Make sure the wood is totally dry before applying the finish. Soak the ends with finish. Apply 2 coats.
Keep in mind not to use too bright a color as it will reflect sunlight and be blinding. Not too dark or it will heat up your buns when you sit on it. The tables I make are entirely from white pine here in Mass. I still see them all over town. Some that are 20 years old. The only problem I've encountered is the feet rotting if left in contact with the ground. I've used patio bricks to raise the legs with success.
The "Man-O-War" is actaully a phenolic-based varnish made by Valspar.
used to be by Mc Closky..then it was good stuff.
Go Stab yourself Ya Putz! Ya think I Parked here?
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