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Can I put Oil based Poly over Water Based Poly?

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Forum topic by 12point posted 06-10-2020 11:39 PM 1002 views 0 times favorited 22 replies Add to Favorites Watch
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12point

193 posts in 4263 days


06-10-2020 11:39 PM

Topic tags/keywords: stain poly pine oil water

I built a table for a friend. Table is made of pine. I used a water based poly but I dont think it will be durable enough. I only put on 2 coats of the water based. Can i put Oil based poly over or do I need to do anything before hand? Table top is stained by the way.


22 replies so far

View Axis39's profile

Axis39

430 posts in 603 days


#1 posted 06-11-2020 12:25 AM

Oil over water works better then water over oil…

Check the cans… Might even see if there’s an online FAQ. But, I would wager that using oil based poly over water based poly shouldn’t be a problem. But, really, don’t trust my word, I’m just some dumb woodworker on the Internet! LOL

-- John F. SoCal transplant, chewer uppper of good wood

View wildwoodbybrianjohns's profile

wildwoodbybrianjohns

2645 posts in 553 days


#2 posted 06-11-2020 12:30 AM

Rule of thumb, generally, is water over oil, no problem; oil over water can be a problem.

Theres plenty of real tough water-base products on the market these days.

-- WWBBJ: It is better to be interesting and wrong, than boring and right.

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12point

193 posts in 4263 days


#3 posted 06-11-2020 12:37 AM

Home Depot is the only option for me for selection…i used a minwax product

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LesB

2858 posts in 4449 days


#4 posted 06-11-2020 05:00 PM

I would not use oil over water but there are some very tough water based polys used for floor finishes. So for a really hard finishlook for a water based poly rated for floors if you want the most durable finish. I have used it on both table tops and wood steps and it really stand up well. I use Varathane brand poly.

Back to the original. Two coats of water based finish are not enough on a pine table top. They were most certainly absorbed into the wood and provide little surface protection. It should have been at the very least 3 and better at 4.
A couple more coats of the poly you are using will work unless the table gets a lot of use and abuse; then go to the floor grade poly. Be sure to sand lightly the original surface before starting and between coats with 320 or 400. After the final coat cures for at least a week or more I like to buff it down using a white 3M pad and carnauba paste wax. If you don’t want a “shiny” finish use 0000 steel wool instead of the 3M pad.

A side note. I find water based poly goes on well with a good quality brush but ambient temperature can be critical. Too cool and it takes to long to dry/cure allowing dust to settle in. Too warm and it sets up quickly leaving brush marks. Usually between 65 and 75 degrees works well….also high humidity can be a factor to consider.

-- Les B, Oregon

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12point

193 posts in 4263 days


#5 posted 06-11-2020 05:46 PM



I would not use oil over water but there are some very tough water based polys used for floor finishes. So for a really hard finishlook for a water based poly rated for floors if you want the most durable finish. I have used it on both table tops and wood steps and it really stand up well. I use Varathane brand poly.

Back to the original. Two coats of water based finish are not enough on a pine table top. They were most certainly absorbed into the wood and provide little surface protection. It should have been at the very least 3 and better at 4.
A couple more coats of the poly you are using will work unless the table gets a lot of use and abuse; then go to the floor grade poly. Be sure to sand lightly the original surface before starting and between coats with 320 or 400. After the final coat cures for at least a week or more I like to buff it down using a white 3M pad and carnauba paste wax. If you don t want a “shiny” finish use 0000 steel wool instead of the 3M pad.

A side note. I find water based poly goes on well with a good quality brush but ambient temperature can be critical. Too cool and it takes to long to dry/cure allowing dust to settle in. Too warm and it sets up quickly leaving brush marks. Usually between 65 and 75 degrees works well….also high humidity can be a factor to consider.

- LesB

Thank you for the reply. Would I be Ok if i lightly sanded the top now with 320 and applied the Oil based? You are right anout the current water based poly soaking in. Doesnt even feel like anything is on there.

View EarlS's profile (online now)

EarlS

4298 posts in 3354 days


#6 posted 06-11-2020 06:09 PM

I’ve done it couple of times with Minwax semi-gloss poly on top of their water based poly. Give the water based poly some time to dry (days) and then lightly sand with fine paper (320 grit is fine) like you would between coats. Apply 3 coats of oil based poly, sand with fine paper between coats.

-- Earl "I'm a pessamist - generally that increases the chance that things will turn out better than expected"

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12point

193 posts in 4263 days


#7 posted 06-11-2020 06:28 PM

I just put another coating of water poly on there. I guess i will see where its at after 4-5 coats. What i just applied was the 3rd coat. My main concern are water marks from drinking glasses on the table when i hand it off. I want enough of a finish to protect against that.

View LesB's profile (online now)

LesB

2858 posts in 4449 days


#8 posted 06-11-2020 07:30 PM

You can use oil if that is you desire. I think several more coats (2-5) of what you are using is fine. Cured poly does not water mark easily unlike Shellac. The water would have to sit there a long time. With that many coats it can take up to 2 weeks or more to be fully cured. It feels dry because the water evaporates but the poly elements actually take more time to cure and bind together chemically. Same applies for oil base.

-- Les B, Oregon

View James E McIntyre's profile

James E McIntyre

1099 posts in 2298 days


#9 posted 06-11-2020 08:18 PM

I would try a test piece before I applied it to your project.
You can sand it first w/220 grit sand paper.

Oil soaks into raw wood and will just float over the water based poly.

When I was in art school there was a rule, Fat over Lean.

This apply to painting oil paints over water based gesso which is very absorbent
Water based poly is not absorbent at all.

I didn’t read all the post above so I hope I’m not repeating some of the great advice already given.

-- James E McIntyre

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Axis39

430 posts in 603 days


#10 posted 06-11-2020 10:40 PM

Okay, I have questions….

I have always been taught that oil finishes take longer to dry than water based products. Of course, historically, oil finishes took a lot longer to dry than they do today. Used to be, you put a coat on and waited forever and a day to do the second and subsequent coats. And, while they skinned over, a lot of the time they were still soft underneath for a good long time. with the oil finish remaining soft, the quicker (and more thoroughly) drying water based finishes tended to delaminate, crack and ripple. Of course, nowadays, you can get oil based spray poly that dries to the touch in less than a couple of hours… But, as a neighbor recently found out, the manufacturer recommended waiting at least 72 hours between application of the oil based stain and coating on top with waterbased poly. Oil could go on right away.

I also know you can throw oil based poly over waterbased stains in just a couple hours.

So, I am really confused by all you guys saying no to oil over water really have me confused.

-- John F. SoCal transplant, chewer uppper of good wood

View LesB's profile (online now)

LesB

2858 posts in 4449 days


#11 posted 06-12-2020 02:25 AM

In the case of poly the ingredients (solids) are carried in either a oil base or a water base but (with out getting technical) poly ingredients react with each other and cure and bond. The latter action is what takes more time. In some cases the oil based actually contains more of the poly solids but newer water based (esp. floor grade) poly has plenty of solids.

I would seriously question “throwing” a oil base over water base in just a couple of hours. Personally I don’t know why you would want to put oil over water based poly in the first place.

Oil based stains take longer for the oil to evaporate (it has soaked in) and that is why the delay before applying a top coat that could seal in the residual “oil” and possibly prevent the top coat from adhering..

-- Les B, Oregon

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12point

193 posts in 4263 days


#12 posted 06-12-2020 03:01 AM

Just an update. I have 5 coats on there (water based) and it has a must more noticeable hard finish to it. Its not soaking into the wood anymore. I have enough for maybe 1 more coat and that should be it. I will try to post a picture.

View James E McIntyre's profile

James E McIntyre

1099 posts in 2298 days


#13 posted 06-12-2020 03:19 AM

Did the water based poly soak into the wood on the 1st coat?

Turpentine also called oil of turpentine is made from pine trees.

The pine you used for you project may not have been fully kilm dried and contains a lot of sap in it causing the water based poly to float and not penetrate it.

Or you could sand it with 320 grit and apply Paste Finishing Wax over it. It works for me.

If possible, I would get out my orbital sander and take off the water based poly.
12point you really asked a good question that spared a good debate!

-- James E McIntyre

View wildwoodbybrianjohns's profile

wildwoodbybrianjohns

2645 posts in 553 days


#14 posted 06-12-2020 07:54 AM

In the painting trade, oil-base over water-base is just something you dont do (unless, in certain cases) you have prepped correctly. It is all about the Bond and it is the Gloss that inhibits bonding. So sanding and primer are the remedies, there.

One “primer” that can be used between different types of urethanes is de-waxed shellac, as it bonds to anything, and anything(almost) will bond to it.

With polyurethanes, it is quite common for floor-refinishers to go over water-base poly with oil-base poly, but sanding first is crucial to take out the gloss and give the new finish something to key into. As said above, as long as the “base” is fully cured, and the gloss cut, then there shouldnt be any issues.

-- WWBBJ: It is better to be interesting and wrong, than boring and right.

View Axis39's profile

Axis39

430 posts in 603 days


#15 posted 06-12-2020 01:59 PM


In the case of poly the ingredients (solids) are carried in either a oil base or a water base but (with out getting technical) poly ingredients react with each other and cure and bond. The latter action is what takes more time. In some cases the oil based actually contains more of the poly solids but newer water based (esp. floor grade) poly has plenty of solids.

I would seriously question “throwing” a oil base over water base in just a couple of hours. Personally I don t know why you would want to put oil over water based poly in the first place.

Oil based stains take longer for the oil to evaporate (it has soaked in) and that is why the delay before applying a top coat that could seal in the residual “oil” and possibly prevent the top coat from adhering..

- LesB

The answer as to why is speed and color.

In a remodeling or construction environment, (which I did for decades) speed is how you make money. Oil based stains have to dry longer. If you can put color and a first coat on, and get it to match an existing item, all in one day, it means you’re ahead of the game.

As for color, oil based poly is yellower, and older projects usually used oil based poly (waterbased products are aa lot more common now than they used to be!). So, to get a new piece to match an old piece, oil based is sometimes required (and easier than trying to match with pigments or colorants, even toners).

There were many times when I stained something (flooring, shelving, etc) first thing in the morning, put the first coat of poly on before lunch, and a second, sometimes even a third on in the afternoon (on a long day). The next day, you can sand and put a final one or two coats on. Waterbased always dried faster… and was the first choice, if it worked color-wise, or wear-wise. But, like I said earlier, in today’s reality, there are oil based polys that dry to a point where you can recoat in just a few hours.

I am still not convinced of the water over oil vs. oil over water…. Guess I will go do some research online later today.

Anyway, I’m glad the OP has found success with more coats of the same product, instead of having to try mixing.

-- John F. SoCal transplant, chewer uppper of good wood

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