Water-based poly?

[Gary Fritz]

I just used a water-based polyurethane for the first time. (I'm no woodworking expert. The last time I refinished anything was my grandma's old oak table, 20 years ago. Now it's time to refinish it and I'm using water-based this time.)

I noticed the grain popped up after the first coat of poly. I assumed that was because the water soaked into the wood. I sanded lightly with

220 grit and applied 2nd & 3rd coats.

It looks pretty good now. Not as smooth as the old poly, but that might have been because the old stuff has 20 years of wear. I think I might sand it again and put a few more coats on -- any harm in that?

It seems to me the water poly isn't filling in the open oak grain as well as the old poly did. This is a kitchen/dining table that gets plenty of use every day, including lots of spills from my 7-yr-old. I want to make sure the wood is appropriately protected from spills and is easy to clean up. Should I keep putting on 4th, 5th, ? coats until it looks like the grain is filled in better?

Thanks, Gary remove xxx's to email

[Leon]

Typically when using water based products on bare wood you should lightly wet the wood surface, let thoroughly dry, lightly sand to get rid of the fuzzy grain that popped up and then apply the water based product.

[Gary Fritz]

Hm. There was no mention on the can. They just said sand with 220 after the first coat. Hopefully that does the job as well.

[BruceR]

Good.

You can. Usually pore/defect filling is best done before the finish is applied, but the only real drawback for you is more work and extra coats.

Keep in mind that water based poly is nothing at all like oil based. They have the same name bit that is about it. Water based poly is much like latex paint, it is not a very good water barrier at all. The finish is emusified, which basically means the dried finish is much like scales on a fish, lots of small "plates" each overlapping each other. Oil based poly is actually cross linked and much more water tight.

I really like water based poly however since it is very easy to apply (I like to spray), clean up, and adds no tint to the project.

-Bruce

[David]

Gary, as much as I like applying WB poly, it wouldn't be my finish of choice for a well used dining room tabletop. You can increase the durability (water resistance, abrasion resistance) of Enduro polys by adding Crosslinker. It is expensive, at $30 for a small bottle, but it goes a long way.

Another option would be to use a more durable finish such as C-V.

David

Gary Fritz wrote:

[Ron Magen]

Gary, No matter what the 'purists' say . . . I like water-based poly for finishing a 'working' surface, like your kitchen table. It's both hard and relatively impervious to liquids & damage.

Agreed, for a faster 'dead flat' & smooth surface, you should have filled the pores first. However, that type of surface is not a necessity but more of a cosmetic choice. To fill the existing grain with the poly, think about

6 coats . . . as a start. {Bare in mind that I consider 6 coats of varnish, etc. as normal !!}. Sand with progressively finer grits between coats. Use 220 for the first AND second, then 320, 400, and 600.

Note, that after the 2nd or 3rd coat the surface is sealed. Even if you see the little 'dimples' of the pores, they have sufficient finish in them to repel spills. Therefore, if you can live with the 'look', and still have it after 6 coats . . . don't worry about it.

Regards & Good Luck, Ron Magen Backyard Boatshop

SNIP I sanded lightly with 220 grit and applied 2nd & 3rd coats.

more coats on -- >

This is a kitchen/dining table that gets plenty of use every day, including lots of spills from my 7-yr-old. I

[Gary Fritz]

Well that's good to hear. From what some of the other posters were saying, I was starting to think it was going to dissolve the first time my son spilled his juice on it. :-)

I have no problem with doing more coats. It only takes about 20-30 minutes to slap on a coat. I did 3 coats yesterday and I can easily do another 3 today if I want to. Except 220 is the finest grit I have, so I'll have to go out to the store to get 320/400/600.

Thanks! Gary

[Gary Fritz]

Hm. Does it harden as it cures? I just looked at the table and I can fairly easily scratch/dent the finish with a fingernail. That would NEVER stand up to my kids.

I just put the 3 coats on yesterday, so maybe it just needs more time.

Gotta say though, the surface is nice and satiny. Just a few dust pips here and there. Not sure why it would be necessary to use the uber- fine sandpapers unless you wanted a glassy finish.

Gary

[MikeG]

You would have been better off filling the with a filler or several coats of thinned and sanded back coats of your finish. Now you don't have much choice but to plow forward adding coats.

The only real way you are going to accomplish the task without adding three, four, five, or six more coats is to sand what you have now all the way down to where it is flat, note, not to the wood, just so it is level, and add another coat or two on the sanded flat surface.

[David]

It will harden over time, Gary, but I'll bet you the contents of my shop that even 3 months from now, you will be able to scratch it with your fingernail (dragged vertically in line with the edge of the fingernail). Moisture left on the surface for most of the day will mar the finish. Short term spills shouldn't bother it, however.

David

Gary Fritz wrote:

[Gary Fritz]

Yeah, I realize that now. The "texture" of the grain doesn't bother me as long as the wood is protected and the grain doesn't collect too much spilled milk and other gunk.

Can't. It's quarter-sawn oak with a very "open" grain. Some of the "pits" in the grain are lower than the surface of the wood.

I dunno if another 3 or more coats will actually "fill in" the grain, but maybe it will help?

I'm more concerned about the durability of the water-based. Unless it hardens as it cures, this will never work out. I can easily dent/scratch it with a fingernail.

I don't suppose it's possible to put solvent-based poly on top of water-based poly? :-(

Gary

[Gary Fritz]

Eeesh. In 3 months my kids could make a mess of my beautiful new finish. How long until it's fully hardened? Hopefully it will get a whole lot harder than fingernail-scratching level!!!

I'm starting to wonder if water-based was such a good idea after all...

[Wes Stewart]

|David wrote: |> It will harden over time, Gary, but I'll bet you the contents of |> my shop that even 3 months from now, you will be able to scratch |> it with your fingernail | |Eeesh. In 3 months my kids could make a mess of my beautiful new |finish. How long until it's fully hardened? Hopefully it will get a |whole lot harder than fingernail-scratching level!!! | |I'm starting to wonder if water-based was such a good idea after all...

What (whose) material did you use. As I believe David said, Enduro makes a crosslinking material that is claimed to improve chemical and abrasion resistance by a factor of seven or so when added to their finish.

I have some of this material but have yet use it, so I can't confirm.

[bridger]

it takes a while.

there are two things going on. first, the water used as a carrier has to evaporate. that takes anywhere from a few minutes to an hour or so. at that point it's dry to the touch, can be sanded and recoated and the new layer will bond chemically. second, there is a cure process where the polyurethane/acrylic does it's crosslinking bit and releases it's primary solvent, usually one of the slower alcohols. this takes a few days, during which it becomes harder and more chemically inert. once this is complete new layers no longer bond chemically, and witness lines and delamination start to become problems.

[Rumpty]

If you put the first coat on too thick that might have popped the grain. What brand are you using? Sand to 22/330 between coats.

[firstjois]

[snip]

I've used it for floor cloths and was shocked at the amount of traffic they withstood, some are 5 years old now and were used in kitchens.

Josie

[firstjois]

[snip]

In my experience it took 7-21 days depending of the humidity, after that surfaces were as good as pre-poly varnishes.

Josie

[MikeG]

Hi Gary

Of course the pits are lower then the wood, that's oaks job.

Lets look at it this way. Suppose you dug a six foot hole in your back yard and the powers that be didn't like it and told you to get rid of it.

Now, you decide to get rid of it by, rather then just filling it in, putting layers of fill over the whole back yard. Yes, I know, of course you wouldn't actually do that but bear with me.

Ok, after about the fifteenth load of fill when half the back door is covered you find the hole is filling up. You've only got three more feet to fill. Kind of like where you are now.

So, where do you go from there. You scrape off all the layers down the three feet and the yard is level. Not all the way back to the original level, just till you reach the level the hole is filled too.

If you have multiple layers of finish on now you should be able to "scrape" that back to a level where all is flat and without hitting the wood. If you're not comfortable with that do a couple of more layers then sand it back. Do not expect large pores to be filled anytime soon by just adding more coats.

As for the strength of the poly. It'll take weeks before it cures fully, oil takes even longer. It'll help if you give each coat twice as long to cure as recommended before adding the next. Also, depending where you live of course, environmental factors can effect curing time. 50 degrees, which it is here right now, is not the ideal temperature for finishes. Finishes like about seventy.

[Gary Fritz]

OK, you had me wondering there. :-) So you're saying just smooth out the finish and don't worry about the pits in the open grain.

I didn't give it all that much extra time, but I did it in the basement to avoid 50deg temps. It was right around 70.

Gary

[Gary Fritz]

Minwax Polycrylic, clear semi-gloss.