Tuesday, June 11, 2013
Tech Tip Tuesday
Well, maybe just one more... coat.
Finish of various types - stains, aniline dyes, paints, varnishes, urethanes and oils are key for protecting both the woodwork and epoxy of a cedar strip boat from the ravages of sun, water and ultimately, rot. They protect your investment of time and money and provide a nice looking boat or paddles.
Finishing - and varnishing in particular - appear to be a mystery to most folks that I teach. I generally hesitate to instruct others on how to finish because most people have some experience in painting and feel put off when I offer finishing suggestions - it's something they figure that they know how to do. Still, for many, it can be a frustrating process.
Mostly, it's about the preparation and the materials.
Let's start at the beginning.
You'll want to sand your project well to get rid of lumps, bumps and irregularities working from a coarser grit to a finer grit paper. How do you know when you're done? When the grit of paper you're using leaves no visible marks. Work with good light and protect yourself from the dust. If you're dealing with an epoxied surface or a hardwood surface, a cabinet scraper may also appropriate for surface prep.
When you think you're done with bare wood, take a sponge damp with warm water and wipe the surface. This will raise the grain. Sand off the fuzz with fine grit paper - say 220 to 320 grit. Then, clean away the dust with a tack rag.
Now that you've got the good clean smooth surface - stop. Read your can of finish - be it stain, dye, varnish or urethane - they come with good instructions. Follow them. This includes thinning the finish with the proper solvent and adding catalysts if necessary to get the finish to cure properly - Japan Drier being one of the catalysts for varnish and oil based paints.
If you want to color the bare wood, now is the time to stain it with the coloring agent of your choice. be it aniline dyes or oil based stains.
People will probably consider me a heathen, but I like foam brushes and rollers for finishing. It's not that good quality bristle brushes don't do a nice job - I have some good ones and like them - it's the cleaning. I prefer to start with a new clean foam brush. It works well for most of what I do - if I had a sprayer, I'd probably consider using that. For some finishes, I do use a bristle brush, but more than likely, I'll use a foam one.
Personally, I use Epifanes brand varnish - it's fairly reasonable in cost and I'm used to working with it. That's not to say that there aren't other great brands out there, because there are and I've used some of them including Interlux, Petit and others. The primary thing we're looking for here besides a good traditional varnish is the UV filters to protect the wood and epoxy from sunlight. Sun is one of the worst enemies of finish. The other is water.
Alternatively, I've used spar urethanes and wiping urethanes from Minwax and System 3 with good luck as well. Oil finishes I reserve for paddle shafts as I find varnish tends to give me blisters, but Watco Teak oil is a fine product for that purpose and can be applied by wiping with a lint free cloth in very thin layers.
Sometimes, you want to paint your surfaces - a good exterior enamel or topsides finish are the best for this application. I've worked with Rustoleum to expensive "yacht quality" paint and really don't see too much difference between the two for my applications, but your mileage may vary.
Actually, with all finishes, one of the major things to remember is thin layers - it's better to apply more layers than to try to rush the process by trying to build a thicker layer and getting runs in the finish that you then have to wait a long time until they are dry enough to sand out before applying another coat of finish. It's a real rookie mistake.
Another real rookie mistake is not applying finish in the right conditions. These include a clean work environment with a relatively low humidity and good lighting. Debris in the finish, milkiness due to humidity and runs or "holidays" (voids") in the finish because the lighting isn't good.
Further rookie mistakes include not prepping between coats - this includes sanding or roughing the surface between coats to get better adhesion, removing the dust with a tack rag and perhaps wiping down with a de-greasing solvent - such as denatured alcohol.
Finally, when you're done, clean up your workplace and clean your tools so they're ready for the next use.