I've had good luck with the oil based polyurethanes. They flow out better than the water based urethanes, and when properly thinned, spray out a beautiful even laying coat. If you use a HVLP outfit, the finish can be applied like a mirror.

The disadvantage of the oil base is a longer drying time and the chance for more dust collecting. The advantage is that the finish will dry hard in cool and cold shops, where the water based products are problematic in the cooler temps. After a few days of curing, if necessary, the poly can be sanded and polished with compounds to a perfect finish.

The precatalized lacquers create a beautiful finish, but they have a steep learning curve for the proper application. They are very temperature intolerant, and can end up crazing and fogging if the humidity is off. I would not recommend this finish for a first timer.

Almost any wood sealer or even shellac can be used to seal the reverse side of the wood. Using the same product that is applied the front, is easier and faster to apply, with both sides being done at the same time. This also ensures that the moisture absorption on both sides will be the same.

Gard

When I renovated our summer home, I used almost a thousand 8' 1 x 6 tongue and grove #2 eastern white pine boards. By far, the easiest and less messy way to install them, was to have them pre finished and sealed before installation. I set up some saw horses with extensions, layed out the boards face side down,and sprayed the back side first. By the time I finished the third batch, the first had tacked up, and I flipped the boards over and shot the faces.

When these dried, I lightly hit them with 120 grit paper on a random orbital sander. After vacuuming them, and tacking them off, I applied a very wet 2nd coat of oil based polyurethane thinned aprox 30 -40 %. When they dried, I again flipped them and put on a lighter second coat on the back. Two coats resulted in a smooth, completely sealed surface.

Take some scrap pieces, and cut off the tongues.  They make excellent blocks upon which you can strike with a hammer, to set the groves of each successive board, onto the previous tongues. Do not strike the tongue of the board you are trying to install. If it is crushed enough, it will show up in the grove of the finished joint. You will have little difficulty with the groves sliding over the tongues after two coats of finish. Little finish will end up inside the grove of the edges.

Any exposed cut edges can be touched up with finish after all the boards are installed. Spraying the boards on a horizontal plane eliminates runs, and using a "satin" poly finish gives a rich natural sheen, instead of the harsh gloss commonly used. Over time, the pine will darken somewhat to a rich patina, with exposure to the natural light.

The poly is very durable and resistant to water, alcohol and many solvents. It can be touched up if it's mechanically damaged, and recoated whenever you want.

Gard

I only spray, and I thin the first coat about 15-20%, the second coat much more 25-40% to get a really smooth final surface. Exactly how much I thin the final coats will depend on the condition of the previous coat (s).

I use acetone for a spraying thinner and clean up, and add one cap full of Japan Dryer per quart. The acetone allows the varnish to smoothly flow out, quickly flash over and dry in cool temps.

If you are going to use a roller, you will need a thinner like a mineral spirits, especially on your first coats. Don't apply it to vertical boards, as you almost assuredly will end up with runs on the subsequent coatings.

Brushing varnish is time consuming and difficult to get a smooth even finish. You have to maintain a wet edge, and if you make a mistake and try to go back and correct it, it will show. Because you have to constantly start and stop the strokes, you will have thin and thick areas. It takes some practice to get a perfectly smooth varnished coating.

An excellent best quality, painter's natural brush is needed, with a thick soft nap and good bristles. A good one is expensive and treat it like gold. If you are going to use the foam brushes, know that they quickly wear out on large projects. They will tear and deposit pieces of foam onto your final finish. Only the best foam brushes should be considered, reject all the cheap plastic handled ones. You want the densest foam available with a rigid, firm tip, not a soft kitchen sponge feeling. I would not recommend a foam brush for this project. It will do poorly on the tongue and slot edge of the wood.

Your roller cover should be a short napped aprox 3/8"-1/2", and also of an excellent quality. Purchase an adjustable frame and cut the standard 7" roller cover in half. You will have more control and less material waste with a narrower cover. I cut mine while they're still packaged on my band saw. It only takes seconds.

Brushing the edges and then rolling the flat surfaces will produce acceptable results. A self contained HVLP sprayer available at most big box stores costs around $150^. It will cut your application time by about 75%. The worse job you do by spraying, will be better than the best application you can do by hand.

Gard

Sorry, I didn't directly answer your question. The thinner is usually the lower number. A poly thinned by 30% would have a mixture of 30% thinner and 70% of poly material.

Gard

Gard, when you say varnish, are you refering to the oil based polyurathane you mentioned eairlier ?

As you can see, I'm not very well versed with wood finishes and chemicals !

I use Tongue Oil on all of my wood finishing. It gives a nice hand rubbed finish. Not too glossy, but gives some gloss. More coats, more gloss. But it keeps the wood very natural looking. I have mostly used it on Hickory and Cherry and it brought out the different colors beautifully and didnt add any fake color. I always sanded between coats for best results.

Good luck

I use Minwax fast dry polyurethane clear satin finish. It has been used in all our furniture and cabinet projects, paneled ceilings, a home's interior walls, a LQ conversion, my daughter's refinished floors and every interior application of varnish that I need. I've used well over 100 gallons to date, and have yet had any difficulties with it. The satin finish gives a new piece of furniture a rich appearance without the harsh glare that a gloss presents.

Gard

Pupsnponies - Your kitchen is BEAUTIFUL!! Tell your husband he should do kitchens full-time.

for anyone else reading this... the polyurethanes come in different "finishes"... I've always used the satin as it's much less "shiney".

I also use 000 wire SOS stuff. (i'm totally blank on what the stuff is called!!) between coats... (wire wool?)  and tacky cloths.

and since I'm old school and don't own a sprayer, I always buy the best paint brushes I can. They make a HUGE difference in how paint or poly goes on.

THANKS...   trying to do too many things at once - not enough memory...