The dreaded task of brushing polyurethane. If you are a professional painter and are reading this thinking that there is nothing to it except brushing it out smooth with an ox hair brush, I’m going to ask you to get rid of your presuppositions for a moment and read on.
Ninety nine point nine percent of the time, when you are putting on polyurethane, or any clear coat for that matter, it is going on something that is a showpiece. That being said, it needs to look perfect. There is not much worse than a newly refinished piece of furniture, done by a well intentioned painter, with sags, or runs, bubbles, or anything other than that of perfection. The smallest flaw in a finish will send any person into a flustered mess every time they look at it. You can have the most beautiful table, made with birds eye maple, inlaid with walnut, and toned to perfection; add one run or sag to the finish, and it’s ready for the trash!
What I’m about to explain, is a way to make your urethane finishes, whether it is on doors, trim, tables, anything, look like they were sprayed on professionally at the factory by a painter that has done nothing but spray finishes for 40 years. Perfect.
I know painters’ mentality, I know the stubbornness of rejecting new techniques, I personally know painters that have painted twenty years that are reading this and saying that they can achieve a great finish by brushing only, and I’ll have to stop you right there and say, no you can’t, I’ve seen your work, and that’s why I’m posting this, (HA). Personally, when I’m charging someone the rates that I charge, I want my finished trim or doors to look so slick, that I could hang them up in a guitar shop next to a curly maple flame top Les Paul, and they would fit right in. Not kidding.
So, what’s the trick? Glad you asked. I’ll bullet out some steps real quick with approximate formula etc. This procedure can be used for stained or unstained wood surfaces, not recommended for floors. If stained, make sure stain has dried according to the stain manufacturers’ specs first.
- Sealer Coat
Seal coat does just that, it seals the surface, it also works as a bond layer for the finish coats. You can buy sealer, or you can make it with a polyurethane and mineral spirits mixture; 75% poly to 25% min spirits. Mix slowly with stir stick and it’s ready to use.
- Lightly Sand
DO NOT USE YOUR DRYWALL SANDING SPONGE! (ouch). Use 400 grit sandpaper, this is important, 220 grit and below is designed for wood. “I thought you are talking about wood surfaces”, you might ask. Once you put a sealer coat on it, it is no longer a wood surface, it is a clear coat, it is to be treated differently now, carefully, like you were handling the damn Mona Lisa!
- Wipe Down
Do not skip this. Polyurethane sand dust is not like lacquer dust, it will not burn back into itself, instead, if the dust is left on, it will feel like 180 grit sandpaper when finished. Take your time, do it right, your charging top dollar, back it up.
I will do a post about toning soon, but quickly, what toning is, is making the surface appearance more even in color, more consistent. If you plan on toning, this is the ideal time in the process to do it.
- Finish Coat Number 1
Polyurethane mixed with a “small splash” of mineral spirits. If you want a ratio, I guess 98:2 will work. No sanding necessary between finish coats, but won’t hurt if you decide to, just wipe clean after you sand.
- Finish Coat Number 2
Same mix as above.
Okay, that is the order of the steps, now lets dive into how to make it all look like glass, even with a brush. STEP 1: Start by using an ox hair brush. You can buy them at your local paint store for under thirty dollars. I guess if you don’t paint all of the time and don’t want to spend the money on a quality oil brush, you can use a cheaper kind, but don’t go too cheap; plan on at least spending twelve bucks. Let’s say that you have a door and a door jamb to finish, start with the jamb. Assuming you’ve masked off your finish walls and floor area that you will be working in, start putting the urethane on the inside of the jamb, where the hinges are, where the door closes, header, now brush it on the trim side, or face, side. Temperature and humidity will dictate how far you can go before the polyurethane gets too sticky to work with, so start small and make sure your “open” time is okay. Now, here is the “key to the mint”, the trick to sprayed looking finishes; It is so stinking simple that I can’t believe the number of painters that don’t do this next step and as a result, let their finishes look like an accountant, or an electrician did them.
STEP 2: You’ll need to purchase another tool, don’t worry, it only costs 2$. A 3 inch foam brush.
Once you’ve put polyurethane on the surface, brush over the wet area with the foam brush, going in the direction of the grain, and making sure that you have no dry spots. That’s it, that’s the secret! I even use it for doors. Now, someone might be thinking to themselves, “Self, I use a foam roller, not a brush, I’ll be okay,” my answer to that is , yes, a foam roller is better than just brushing on with your ox hair brush and calling it good, but not as good as the foam brush. The roller leaves a chance for bubbles, doesn’t get in the grooves of higher end trim boards, and really just flattens out the poly instead of the “squeegee” effect of the foam brush. If that doesn’t convince you, watch someone put their finish coats on hardwood floors, you won’t see a roller in their tool box anywhere.
STEP 3: Once you’ve completed clear coating your project, go back and look for drips or runs every few minutes until it dries, and just wipe the effected area with the sponge, it will dry down. Allow to dry, and start back at step 1 for your second coat. Two coats, on top of the seal coat is plenty unless you are doing a musical instrument or finishing a piece that you will want to polish to absolute glass like finish.
Make sure that you throw all of your rags that have been in stain, finish, or mineral spirits in a bucket of water before you throw them out, they will catch on fire if not.
I hope this helps, I know it works, it’s how I finish. I taught it to my first year apprentice last week as he worked on his first stain and finish job with me, and in 1 hour, he was producing a professional look.