Finishing 1500 sf of birch T&G

[Rich Zimmerman]

I've got 1500 feet of birch tongue and groove that I'd like to seal. I plan on sealing before I put it up, and seal on both sides. I've been told that sealing before you install is best because you don't get unfinished lines develop as the boards shrink. I've been told to seal the top as well as the bottom to prevent the boards from cupping over time.

Half of this will be on an indoor ceiling, the other half will be on a soffit overhang. We're in Tucson, so very very dry most of the year. We plan on sealing clear to show off the wood.

So the question is what's the best / quickest / least painful method for sealing? I've read about oils (tung, linseed, etc), but 1500 square feet with a day drying time between coats seems like it'll take a year to get through the whole bundle. I was leaning toward spraying a catalyzed lacquer because it would be fast, but I'm a bit concerned about how well it'll hold up in the soffit (albeit it's so dry here that maybe I'm overthinking things?). I've also read about people spraying poly through typical airless paint sprayers. Maybe that's the solution?

Thoughts?

[Maurice Mcmurry]

For a project that size I would be looking for a way to use the airless, Water based polyurethane is my first thought.

[Rich Zimmerman]

Thanks. The water based polys tend to not bring out the grain as much as the oil ones, right? I'm guessing that they also will not yellow over time?
Do you think I could get by with just a single coat (it's way up on the ceiling and soffit, so it's not like anyone will see it up close). (As I type I'm thinking one coat is a bad idea, but the thought of sanding 1500 sf on both sides (so 3000 square feet) makes the tendons in my hand hurt already).

[Jack Frederick]

Not sure what length your pieces will be, but years ago I re-sided many house with cedar clapboard which I primed and put the first coat of finish color on front and back before putting it up. I put up two 2x4x30’ rails and used 16p nails as the separators every 3”. Tedious at best but it came out really well and was actually pretty efficient. Why sand both sides?

[Jim Becker]

Some waterborne finishes will "yellow" over time and some less so. But not anything like an oil based product will because of the nature of oil. Some waterborne finishes, such as Target EM2000 and to an extent EM8000cv intentionally provide an ambering effect as comes with an oil based finish...EM2000 in particular, is an emulsified alkyd product that looks like oil based when cured. Bottom line...depends on the product and what you really want to accomplish. If the warmer color is good, you can also just use shellac, particularly if this is for a ceiling application. It's fast to apply and fast to dry...even faster than waterborne.

[Rich Zimmerman]

Thanks. That's probably what I'll do.

Why sand both sides?

Isn't sanding pretty much necessary on poly in-between coats?

[Rich Zimmerman]

Thanks Jim. Any experience with "conversion varnish"? I called the company that mills this and asked what they do when they're asked to seal it at the mill and they apparently use conversion varnish. Their version only had an 8 hour pot life, so it may not be a particularly DIY friendly product, but the guy there seemed to swear by how it doesn't yellow and creates a really nice looking, hard protective surface. (Although their main consideration is probably that they can stack and wrap the product after about 12 hours of dry time)

[Jim Becker]

The EM8000cv I mentioned is conversion varnish...waterborne. I don't use solvent based finishes as I do not have a safe environment to spray them.

[Maurice Mcmurry]

One coat of a two part product would certainly save time. Getting all of that staged will be tricky. I have used two part waterborne epoxy bathroom paint. I devide the paint and catalyst with careful measuring so I do not have the whole batch going off at once.

[Tom Bender]

Staging will be one of the keys to a good result. I think Jack sends us on a good path. A mile of saw horses with spacers to keep the pieces apart, both for application and for sanding before and between coats. A stack of material with one piece on the horses. As you do each piece your two helpers set another one and you back away from the stack. Overspray would be a problem. Better to go with wipe on or brush on.

So here's my schedule;

1. Sand and blow dust off, flip and do the other side. Restack.

2. Spray on a little moisture to raise the grain and sand that off. ROS should be up to it. Probably can skip this step for the back side.

3. Vacuum both sides as you restack.

How long and stiff is your material? you may need 4 horses which makes application tricky, or not if you have a second person applying plus the two handlers.

4. Clean the area and wait for a windless day

5. Wipe on a coat, back side first then flip and wipe onto the finished side.

Those horses should have triangle stock on top so they only leave a line in the finish. Spacers would be helpful.

4. Restack when dry.

5. Sand the finish side. Repeat until done.

Are you doing this outdoors? Dust may be a problem. Shellac may be a solution but will have to be refreshed often.

[Rich Zimmerman]

I thought I'd give an update in case anyone stumbled upon this thread.

I didn't want to ship a large quantity something in that I hadn't used before. I considered bringing in just a gallon of the Emtech CV to give it a shot, but shipping right now is crazy expensive and I honestly didn't have the time for two shipping cycles, so I decided to go with what was local.

Three options: Sherwin Williams Pre-cat Lacquer, Gemini GemCoat pre-cat lacquer from Dunn-Edwards, and Mohawk DuraCoat from a wood supply shop locally. Zero water-based products locally. I had used the Sherwin Williams product before and have found it to spray easy with HVLP and performs very well. My kids eat on a mesquite table I finished with it about 7 years ago and it still looks wonderful despite being subject to crazy kid-based abuse. However, SW has gone crazy on retail prices. $72/gallon and now they make you buy the catalyst separate (another $55), so we're nearing $130 just to shoot 1 gallon. They used to catalyze it in store for free, but they don't do that anymore. I guess SW has decided retail customers can stick it, and they'll concentrate on commercial customers exclusively.

Between the Mohawk and the Gemini I decided to go with Gemini. The Mohawk doesn't seem to have any UV inhibitors in it, and that's a pretty big deal in southern Arizona, plus it has a lower solids percentage, and correspondingly lower coverage..so I figured it's basically more diluted than either of the other products.

I'm thorough about half of my T&G. I've sprayed about 6 gallons so far. I used a Graco X5 sprayer that I've used for latex paint before with a 311 tip. It went through great, but converting to lacquer was a bit problematic. I'm incredibly meticulous about cleaning that machine, but even with it being as thoroughly clean as I could get it inside, there was still some residual latex in the system. It showed up in a clogged filter in the first round of spraying. It didn't really affect the spray at all, but it slowed me down a bit.

One thing I've noticed. The manual states that if you're coming back to spray within 48 hours, just tightly cover the container with the hoses in it with saran wrap or whatever you have, release the pressure in the system, and clean the spray tip. That's what I did. The next morning I noticed that the supply hose in the lacquer had become completely misshapen and soft. I also noticed that the little gasket in the spray head had started getting soft. I'm thinking that the X5 isn't really designed for a solvent as aggressive as lacquer. I might need a new supply hose and a seal overhaul after this is over.

So far everything looks great. I didn't go with a sealer because it's just too much of a pain with an airless to switch product mid-stream (my shop is only big enough to do 1/8 of the boards at a time, so that would be a LOT of changeovers). The GemCoat is self-sealing, but you suffer in the sanding.

[Jim Becker]

I'm thinking that the X5 isn't really designed for a solvent as aggressive as lacquer.

Indeed. The solvents will do a number on many plastics and other materials. Airless systems really are focused on "house paint" type products for the most part.

[Tom M King]

That's not true of the pro rigs. I'm not sure about the homeowner versions, but I doubt they expect anyone would use one for solvent based.

I've sprayed many gallons of oil based through my pro rig, and even Moisture Cure Urethane through it several times, and it has never suffered. MCU has every solvent on the dangerous list in it except for gasoline.

[Maurice Mcmurry]

My Dads rig is a Wagner hopper with a diaphragm pump. He kept Lacquer in it continuously for well over 20 years. He used at least it every week and was careful not to let it dry out. It still works. His products of choice were S.W. Vinyl sanding sealer and ML Campbell M.R.E.

[Jim Becker]

That's not true of the pro rigs. I'm not sure about the homeowner versions, but I doubt they expect anyone would use one for solvent based.

I've sprayed many gallons of oil based through my pro rig, and even Moisture Cure Urethane through it several times, and it has never suffered. MCU has every solvent on the dangerous list in it except for gasoline.
The solvents on lacquers, etc., are way more problematic for plastics and other materials than anything oli based. But it's good to know that a "pro" airless is better suited to stuff that melts other stuff. :)

[Maurice Mcmurry]

Going back and forth between products can create real problems. Lacquer will loosen up every thing that was left behind by Latex, Oil and Shellac products you have used before. As mentioned above.

Lacquer Conversion Kits (https://www.graco.com/us/en/homeowner/products/paint-sprayer-accessories/lacquer-conversion-kits.html)

[Tom M King]

Moisture Cure Urethane that I've used has Xylene, Tolulene, Acetone, and I forget what else in it but the list is long. If that didn't hurt mine 20 years ago, which it must not have since I'm still using it and have never been in it, I can't think of any lacquer that would be a problem.

I sprayed an aircraft hanger floor with white MCU, and some years later sprayed a flip house wooden floor with it because it had so many small rooms that I didn't want to stay in there, even with supplied air, long enough to squeegee it on.

I forget when the aircraft hanger floor was done, but do remember the house floor was in 2012, and the hanger was some years before that. This is the same pump I used in the video about the garage doors. All I've ever done for maintenance is put oil in the pump occasionally according to directions, and keep Pump Armor in it.

It was not a top of the line pump when I bought it sometime in the 1990's, but it is a Pro unit.

I'm sure the rig manufacturers have charts that tell you what finishes a particular unit can spray, including solvent based lacquers. I doubt they spend extra on seals for the lower end ones.

Edited to add: I don't think there was such a thing as a homeowner level airless sprayer when I bought this one.