Do a Google search for varnishing techniques and you will get thousands of results with likely all different techniques. Despite some folks thinking that their way is the only way, I feel that the best technique is the technique that you are the most comfortable with and that yields the best possible result within the desired time investment. Below I share my technique. I try to keep things as simple as possible, but I still want that mirror finish like everyone else. It definitely requires some time and effort and often the finish work can be 20-30% of the entire project. Let me know your technique in the comments section or if you agree/disagree with any of my steps. I am always up for learning and improving.
- I sand everywhere I plan on varnishing as smooth as I can down to 200 grit. You want the surface smooth, but don’t worry about getting everything 1000-grit, glass-like smooth. The coats of varnish will smooth things out and you can use that 1000-grit paper (wet) on the final coat if needed.
- Shop vac the boat and the whole shop area. The shop usually needs it anyway. For the boat, take your time. Use a nozzle attachment that will suck right on the surface pulling all those little dust molecules out. I typically do this a couple of days before varnish so everything has time to settle.
- I then spray the floor with water. I use one of those insect sprayer tanks that you pump up and I just put down a very fine layer of water around the work area. This keeps the dust from stirring up while you walk around. My workshop is bare cement basement floors and they hold a ton of dust. I suppose if I had that epoxy-based cement coating on it, this step may not be needed. A project for another day.
- I wash the area to be varnished with denatured alcohol flipping the rag frequently to always have a clean rag area.
- I apply the varnish with a 4″ Shur-Line Mini Roller (roll and tip). I haven’t found the roller material to make much of a difference. Just make sure it is a material designed for varnish. I lean toward foam. I use the Shur-line stuff because it does the job well, it is inexpensive, and readily accessible (Amazon and Home Depot). Keep in mind that this is an important step in getting the right amount of varnish on the area. When you tip, you only want to drag the brush over it once and not have to go over it again. If there is too much varnish, you will get sags. Booo! Sags are a vicious time suck to sand out. Too little varnish just means that you won’t cover adequately. That is OK because you can get it on the next coat. Always lean toward too thin.
- I then go back and “tip” with a foam brush. The brush should be slightly loaded with some varnish. You don’t ever want a dry brush, but you also don’t want it dripping wet. Remember, try to just drag the brush over the coating one time to smooth out the roller lines and air bubbles. I know it is hard, but fight the urge to keep stroking it until it dries.
If this is new to you, PRACTICE first. Find an old piece of lumber or in my case, the bottom shelf of my workbench. Give it a quick sand and have at it. Make the area you are varnishing vertical so you can see if you get any sags. Varnishing a level horizontal surface is easy, but you will eventually have to do something vertical so you might as well get it right before you need to spend hours sanding sags.
I usually only do small sections (about 3′ x 3′) at a time to make sure nothing cures before running the foam brush through it. After I tip that section, I start rolling the next with about an inch or less of overlap. Once completed, I let the first coat cure for 2 days and then follow with a light sanding with 400 grit. Be sure to tread lightly and stay away from the edges. All you are trying to do is scuff up the surface a little and take down any small dust bumps. Then I repeat everything starting at the alcohol wash step.
Many say there is no such thing as a last coat of varnish and I have not quite mastered what exactly to do after my time, patience, or varnish has run out. Some projects I have left untouched and some I have wet sanded with 800 grit paper and bronze wool, but that is an awful lot of work. Take a look at your final result and decide for yourself. If it is a beautiful mirror finish, leave it alone and be happy! If not, wet some 800 grit and test it on a small area. Just know that the sandpaper will leave scratches that will need to be rubbed out with fine bronze wool or something similar. I had some success on my paddleboard and am probably going to follow the following process again.
I applied 6 coats of varnish. Between the 4th and 5th coats I sanded very lightly with 800 grit. Between the 5th and 6th, I sparingly spot sanded any dust bumps with 800 grit. By sparingly I mean that there was one small 4″ section of a couple of dust bumps and that is the only part I sanded. If it were not for that small area, I would not have sanded at all. I then made sure to re-coat the very next day to ensure that I would have a chemical bond since I wouldn’t have the bond from sanding scratches. The result was an excellent finish with no final coat sanding and buffing.
I never do less than 4 coats on anything that will get any significant exposure to sun and water and I use Interlux Schooner Varnish.
Thank you for reading!