Join Date: Mar 2009
Location: Summerville, SC
The green colored treated lumber you see at Lowes isn't a good choice either-- you need to wear a thick dust mask when you cut it, and it usually isn't very dry--- meaning, it will warp on you as it dries.
You have several options though. Keep in mind that NOTHING stands up to the sun long term, but some work better than others.
1) Use an exterior grade wood, and this may not be too hard to find if you look around. Cypress is wonderful (light colored and very easy to cut, looks like pine). Redwood, red cedar (eastern or western), white oak, mahogany. These all make great exterior wood items. They don't rot easily. Since this is a hanging sign, it may not really be a big issue (can dry back out easily) but woods like pine or poplar will deteriorate quicker in all the rain we get typically.
2) For the clear coat, use Spar varnish. It's specifically made for outdoor use, and it works just like polyurethane. Lowes has a ton of it. Don't waste $$ on aerosol cans, though, they take FOREVER to build up a good coat.
3) For paint, any waterbase latex for exterior will work just fine. Scuff sand the spar a bit if you must paint over it. Never paint over glossy slick spar or poly. Always scuff it up with some 180 or 220 grit sandpaper to give the paints something to grab. GLOSS PAINT will last longer. It seems to make a much more stable seal than low-sheen options like eggshell or matte.
For contrast with the letters, take your power sander and grind the stain OFF of the letters, revealing the lighter colored wood underneath it. Put the spar varnish over the whole thing as usual. Will look nice.
FWIW I am not a paint artist at all but really it's quite doable to hand-paint the letters with paint. I've done it several times with the wooden signs we have on campus here at the Seminary. Just go to AC Moore or Michaels and buy yourself a small pack of various sizes of artist paint brushes. Any of the common middle-range price brands should work, ask someone to help you select them.
True freedom is not the freedom to do whatever you want; that is slavery in disguise.
True freedom is the freedom to always do what's right.
-- Old Stoic philosophy.
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-- Eaton C. Bass