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FrenchGirl
Can someone explain what polyurethane is for?

Can someone explain to me what polyurethane is for?(not sure that's what it's called or how it's spelled. sorry)

I stained my living room floor of rough/rustic pine planks with Minwax floor stain. Now the Minwax says it "seals" right on the label. But the guy at the store said that I needed to 'seal' the floor with a polyurethane after staining. So now I am confused. Does the Minwax actual seal the wood? What is the purpose of applying a poly on it.

A. Spruce
Re: Can someone explain what polyurethane is for?

First and foremost, Minwax makes great stains, but their poly and other top coats are absolute garbage!!!!

Polyurethane is a clear finish that has replaced lacquer and shellac because of it's more environmentally friendly. There are different types/grades of poly, make sure you're using one rated for floor use before applying or you're going to have a huge mess on your hands when the coating fails.

Not sure what your stain is capable of without knowing more about it. Some stain products are a stain and top coat finish all in one. These are a poor choice for most projects, particularly a floor because the stain is held within the top coat finish like a paint, rather than a penetrating stain. What is the exact brand and product description of the stain you used?

FrenchGirl
Re: Can someone explain what polyurethane is for?

The can says "Minwax Floor Stain" and "Stains, Penetrates, and Seals"

I still don't know if I should leave the floor with just the stain and skip the polyurethane, or do floors absolutely have to have poly on it.

jkirk
Re: Can someone explain what polyurethane is for?

definitely put 3 or 4 coats of polyeurathane on the floor, the stain does seal it in a way but its there to give the wood color. the poly is what seals the wood from moisture and gives it extra durability as the finish coat will scratch before the wood itself does. if you get a scratch you can buff the finish

Sombreuil_mongrel
Re: Can someone explain what polyurethane is for?

If you are finishing a pine bookshelf or a cherry desk, then no further sealer is needed before the varnish step. Floors are a different animal. If your topcoat demands a particular sealer, use it; it's all about the bond between the wood and the finish. Sometimes a very hard-wearing topcoat makes a bad first coat onto the wood, and really needs its primer/sealer to grip.
On an oak floor, you need the sealer coat to get a good start on filling in the very open grain. Varnish alone is very slow to fill oak's porous surface.
Casey

A. Spruce
Re: Can someone explain what polyurethane is for?
FrenchGirl wrote:

The can says "Minwax Floor Stain" and "Stains, Penetrates, and Seals"

I still don't know if I should leave the floor with just the stain and skip the polyurethane, or do floors absolutely have to have poly on it.

As I said in my first post, Minwax top coat products are utter garbage, so I can assure you that you will need a proper polyurethane top coat. You will want to use a coating that is specifically rated for flooring or you will be wasting both your time and your money. I have never refinished a floor, so I cannot recommend a specific brand of poly to use.

Re: Can someone explain what polyurethane is for?

Make sure you use a polyurethane meant for floors.

Polyurethane replaced shellac because it is far more durable. I don't see how it would be environmentally friendlier given the VOCs and hydrocarbons. Shellac is excreted from bugs and is dissolved into alcohol.

A. Spruce
Re: Can someone explain what polyurethane is for?
drooplug wrote:

I don't see how it would be environmentally friendlier given the VOCs and hydrocarbons. Shellac is excreted from bugs and is dissolved into alcohol.

You've obviously never been at the business end of the bug during it's "excretion" ... ;):p:D

JLMCDANIEL
Re: Can someone explain what polyurethane is for?

Yes, you need to apply a finish. Pine is a softwood and wears easily. The stain doe not protect the floor from wear. I only use OldMasters brand poly. It is easy to apply because it has very good self leveling properties and dries to a hard durable finish. You have the choice of either and oil based or a latex based poly. The latex based poly is clearer but not quite as durable the oil based will add a slight amber tint to the finish but is more durable. The self leveling properties means that it hardly shows brush marks. You should apply a minimum of 3 coats.

Jack

JLMCDANIEL
Re: Can someone explain what polyurethane is for?

To add to your confusion, you can get poly in High Gloss, Semi Gloss, and satin finish. For a floor I refer Semi Gloss.

Jack

ordjen
Re: Can someone explain what polyurethane is for?

If the Minwax stain is used, no sanding sealer is neccessary as the stain sets the grain. It you want unstained wood, a sanding sealer is recommended.

At Home Depot, Varathane Floor Oil finish is the more premium and more expensive. It contains microscopic aluminum oxide particles to increase wear. That is the stuff sandpaper is made from. It requires a minimum of two coats over a stain, but 3coats is highly advisable to increase the long term wear. As mentioned, it does have a slight amber tone to it and will get more so with age. This is important if a light, whiteish stain is used. Better then to use the water based.

Water soluble urethanes are increasingly popular because they dry quickly and multiple coats can be put on in a day. They also have relatively little odor. A minimum of 4 coats is generally recommended with these because the film is thinner. Many feel that the water borne products lack the warmth of the oil based due to their crystal clear color. This can be partially alleviated by using a de-waxed, or "universal sealer" as the first coat. DO NOT use regular shellac, as it is not compatible with urethanes. Shellac gives a nice warm patina which helps the water bourne urethane avoid that plastic look. Shellac is also very fast drying.

Allication of floor finishes is normally by use of a floor applicator on a b room stick; lambs wood for oil, synthetic for water based. A brush is used to cut in the edges. I have seen the pros just pour the varnish on the floor and kind of squeegee it
along the floor in a kind of figure eight pattern.

You definitely want to follow the directions on the can. Urethanes are kind of funny in that they have a window in which additional coats can be applied without sanding, usually between 4 to 12 hours. Once thouroughly dried, it has to be "screened" or sanded before additional coats. So, try to stay in that 4 to 12 hour window to avoid repeated sandings. Of course, if you have managed to get crude into the varnish, it can always be sanded and dusted before continuing.

As to how environmentally friendly shellac is: it is grain alcohol (de-natured) with shellac flakes desolved in it. What is more organic than beatle droppings!:) It is harmless enough that medication pills are coated with it! It is about as time tested as a product can be. The Chinese have been using it for a couple thousand years! I guess they didn't know that there is no lead or melamine in it! :)

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