Posted by Jon Harl on February 18, 2004
D. BernhardtHey guys, Thanks for all the great feedback on my carving substrate question. Now if I want a natural wood finish for that mahogany sign what would you recommend? It's got to hold up outside in California weather-lots of sun.
Hi again Jon.....I've had alot of luck with the sikkens system (slightly different than Mikes) although never did the test piece. Will do one of those this summer. However what I do is carve (usually mahogany) and apply cetol-1 ...Dark oak and wipe off, then their mahogany each, a day apart...do it last thing as it stinks like .. I use a foam brush and you can choose the colours best suited to your taste but two or three coats will give good service. Of course I'm also treating the back at the same time. Next day again I spray on a coat of TGL (sikkens again) varnish. It isn't actually a varnish and the 2 must be combined ( cetol-1 and TGL). 2 to 3 coats a day apart should be just fine although 3 is ideal. Also i use an HVLP and put down a good coat and rarely (if ever) thin it down. Now signs that face south and in heavy traffic areas will require a cleaning and a fresh coat of TGL every 3-4years. BUT...they are not blistered or cracked just the film is dull and showing wear. The north side will last twice as long. Also to note...the satin finish will dull to flat after a year or so and the gloss to a nice satin...so I use that one.
Mike Jackson
Hi Jon,
I will be watching this post along with you. The only product that I "hear" works is Sikkens two part clear, sold through automotive paint shops. I never tried it, so I can't give any reports.
Here's what I did:
I sandblasted a 2" x 12" piece of redwood with two rows of squares going across the length of the six or seven foot length. Each squares had a raised basic letter. Each of the squares also had a raised border. So, in the end I had roughly 14 test sections. I left one unpainted and unprotected. One got Thompson's water seal. One got redwood colored transparent stain and one was coated with several coats of reddish colored latex paint. Another square section was primed with blockout a couple of times and painted with One Shot enamels. The remaining squares were then individually varnished with all the popular clear varnishes of the day. Sikkens wasn't one of them unfortunatley. Each square was labeled and I made a little stand to hold the panel upright and facing the south sun. I put the test piece on the roof of the shop and would go look at it after six months to make notes. After only one year, I took it down and brought it into the shop so show customers (when needed).
The bottom line was the varnishes all crapped out. The stained area still looked good but a bit dry. The latex still looked excellent. The enamel painted one looked fine. The Thompsons area had grayed along with the unfinished one. When a customer insisted on clear finishes, I would bring the panel out and let them pick the one they wanted from the cracked and failing varnish tests. With that tool, I can't recall being pushed into a clear finish by another customer.
In Jackson Hole, we have boardwalks with covered canopies in quite a few areas of town. I never had a problem using clears if the sign was covered from the sun and major weather. Those signs looked great for years and years. We did a sign for a jeweler with two tones of stains and several glossy coats of varnish. It had incised carved gold letters and was very classy. The sign was mounted under the eave facing north. It held up GREAT for seven or so years until they moved to a new location. When the sign was exposed to the east sun, it showed signs of wear within a year and had to be redone by the new shop a while afterwards.
Some will tell you coastal areas are particularly hard on finishes. Others suggest extreme heat is tough. We have intense high altitude UV here in the mountains. Some have problems with humitidy, mildew, water sprinklers and so forth. With the expansion and contraction of the wood, I just haven't seen the clear finish that can handle it.
Maybe someone will come up with a time tested varnish or finish, but I can tell you firsthand, you cannot listen to the salesman at the lumberyard! I've been in there numerous times when a customer asks for a clear varnish for outdoors and they talk as though they know things work. A lot of polyeurethane goes out the door.
Mike Jackson
Robare M. Novou
Yes, the polyurethane does go out the door. Try using the straight clear urethanes. Such as the brand you mentioned, sikkens, or house of kolor, or ppg/ditzler. They are a two part paint, meaning you mix the base with a hardner and spray it on. I never tried brushing or rolling.
That would be a great test panel worth doing again using varnishes, urethanes, latexes, and acrylics.
RMN
Denver Chapter of the Letterheads