I had read many times before about the three pillars of a craft: Design, Construction, and Finishing. Let me tell me you, after this experience, I truly realize now and appreciate the amount of effort and knowledge and true craftsmanship that goes into finishing.
I posted on multiple forums, read many an article, and watched a veritable slew of finishing videos. Videos about outdoor finishing, videos about varnish finishes, articles about the pros and cons of diluting your polurethane.
I finally decided to go with The Wood Whisperer’s recommended method of A Better Way To Apply Spar Polyurethane. It’s basically to dilute your poly with 50% mineral spirits, naptha, or paint thinner. I opted for naptha because of the higher flash time so I could try to get 2-3 coats a day in when possible.
All in all, I’ve “gone over” each and every surface of the chair 14 times so far and plan two more before calling it done.
- 1 initial sanding at 80 grit (not needed with new lumber but since this was reclaimed from a bookshelf, I had to get rid of the dirt and stain and discoloring of age). This was done pre-assembly after I had all the cuts made.
- 1 initial sanding of 150 grit for mechanical tooth for which the varnish to bind
- 2 initial 50/50 poly/naphtha for the base coat
- 1 light sanding with 400 to knock down the unavoidable particulates
- 8 more coats of the 50/50 ply/naptha mix with another round of light 400 grit sanding anytime there was >= 24hrs since the previous coat (with diligence, i was able to keep that down to only once) thus,
- 1 more light sanding in the middle because I let a ~30hr cure after the 4th coat
This weekend or maybe Monday, I plan to finish it up with:
- 1 more light sanding with 400, and
- 1 more light sanding with 0000 steel wool
I did use a brush and 100% un-cut poly for the underside of the chair since I didn’t care if there were brush strokes and/or bubbles there. I just wanted the protection that the poly provided there so I put 4 coats of full strength poly on the unseen undercarriage.
This finishing endeavor was quite a learning process. I think it came out great as, thanks to wiping, there are neither any brush strokes nor any bubbles. However, due to all the ‘intricacies’ in the little hard to get to spaces between slats and all the corners and the like, it truly became a tedious journey. I am all about the mentality of “it’s about the journey more than the destination” but when the finishing section takes even longer than the whole rest of the project combined, I can’t deny that I was really hankering to have a seat in this thing!
It’ll surely make me appreciate it a lot more though!
I don’t have many pics of the polyurethane process because it was pretty much the same thing over and over again.
I’m thinking the next intricate outdoor project I build is going to be finished simply with danish oil or something. Sure, it’ll need to be re-applied annually but I think I’d prefer one or two coats a year instead of 14-16 once. Especially on something like a chair that is going to get used and abraded a lot.
The next blog entry will show the fully finished surface with the piano hinge installed. The last blog entry after that will be my “Hall of Shame” post where I point out my mistakes and flaws so I can better learn from them and avoid them in the future. Stay tuned!
-- Tim Bridge, Northern NJ,"Education is when you read the fine print; experience is what you get when you don't." Pete Seeger