Wood finish can be applied with 2 forms of polyurethane formulas: oil-based one and water-based one.
The question here to find out is: Can you put water-based poly over oil-based? Let’s find out with us!
Basically, the answer is Yes, you can.
But the procedure requires several steps and materials to be followed strictly.
In this article, we will find our why and how we can.
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What Are The Differences Between The Two Formulas?
Polyurethane (in short, poly) is a finishing layer, functions like a protective coating that offers protection care to the surface from wear and tear.
In most cases, both water-based and oil base work the same and can work well being applied separately.
They even share some similarities; yet have significant differences that if you master them well, you can bring out the best in each of the two.
Oil-based poly on 2 1/4″ Red Oak. Above: Water-based poly on 2 1/4″ Red Oak
Water-based Poly
Water-based poly has a crystal clear color.
When you apply water-based poly, the color stays clear for a lifetime.
It also dries faster, which helps shorten the producing process, especially when you need to apply several coating layers on the surface (dry out time: 4-6 hours)
Consumers also choose Water-based poly to reduce chemical smell.
It is an acrylic product, thinner, but has a harder coating than Oil-based.
Despite all those factors, if you wonder “can you put water-based poly over oil-based stain”, then the answer is yes, but only when the stain has been thoroughly cured.
Most important, water-based poly is a rather expensive product.
But the value that you gain from reducing working hours and strong chemical smells is popularly considered.
Oil-Based Poly
On the contrary with the water-based poly, the oil base one is often consumed for thicker and darker coating layers.
The texture of the oil-based is much thicker; hence it makes your wood surface look yellow.
Even though oil-based is a thick one, it is also softer, can be more susceptible to dents.
Drying time is much longer (one coating of oil-based poly can only be applied to the hardwood floors every 24 hours).
And during the working process, we normally advise guests and pets to be out of the house to avoid the stink.
The most unique thing about oil-based is the amber hue color, which continues to amber and get darkened from time to time.
In brief, these photos visually show the differences between the two:
How To Apply Water-Based Polyurethane Over Oil-Based Polyurethane?
Back to the question: can you use water-based polyurethane over oil-based polyurethane.
The exact question here should be: How to apply water-based polyurethane over oil-based polyurethane?
In this part of the article, we will show you the steps to apply those 2 formulas:
1. Surface Treatment Methods
Make sure that the first layer of the oil-based is fully cured.
In case you are not sure if the curing time is enough or not, we recommend waiting up to 30 days before deciding to apply water-based polyurethane over oil-based polyurethane.
Even when the surface touches cool, it might not be dried out thoroughly, and that will ruin the whole process.
One method to check the level is by using sandpaper: if it produces light and fine powder, then the surface is ready to go.
How long before can you put water-based poly over oil-based paint?
2. Use Grit Sandpaper To Buff The Old Finishing Layers
This step can be done with sandpaper or power buffer.
Just use a light touch of buffing to avoid damaging the oil-based finish that was applied before.
3. Vacuum The Surface Thoroughly
Use a dry cloth for smaller surfaces and vacuum for the larger ones.
Then carefully vacuum the floor one more time to really get rid of any tiny dust that you cannot see.
4. Wipe It With a Clean Cloth
If you think the cleaning with a vacuum is enough, then re-think.
The key factor that affects the process of apply water-based polyurethane over oil-based polyurethane is the dust itself.
In this step, mineral spirits bring the best result: damp the cloth with mineral spirits to get rid of all the dust.
5. Protect Yourself With Adequate Ventilation
Do not underestimate this step, since it directly affects your health system.
That helps prevent dust and sand from getting to your lungs, and also reduces chemical damages.
6. Respirator
Choose the decent one (highly recommend the respirator that is rated for organic fumes).
7. Ensure The Workplace Is Dust-Free
We have to mention once again, cause it is never enough reminder: make sure that you vacuum, wipe all the surfaces in your working area.
Remove any potential dust sources (such as rug, mat, tapestry…).
Trust me, you really do not want to have any dust floating in the room during the process; or else the answer to your question of “can you use water-based polyurethane over oil-based polyurethane” is totally a no-no.
8. Prepare Your Polyurethane
There are 2 types for your consideration: full strength or half strength.
If you want to have a whipping varnish, use the half-strength only.
The drying time is faster and also easier to sand.
9. Let Dry & Cure
Now is the time for you to apply the first coat, using the clean brush then let it dry and cure.
The waiting time depends on the brand you buy.
Mostly the water base poly dries quickly (4 hours).
Some might take longer (6 hours).
Please check the instructions carefully before applying and reapply.
10. Use Grit Sandpaper To Smoothen The First Coat
At this phase, you can use the sandpaper of 280 or even 320 grit.
However, do not press it too strong to make sure you do not sand through the surface.
11. Wiping
Now, wipe, wipe, wipe, and vacuum vacuum vacuum all over again.
In this phase, you can use a tack cloth or sticky cloth and end with a damp cloth.
Can you put oil-based polyurethane over water-based polyacrylic
12. More Coating
Remember to leave each layer to totally dry, then grit smoothly.
Use a tack cloth to wipe again before coating the next one. Then allow it to cure completely
13. More Gritting
Use the same technique and materials as before (mineral spirits, power buff, or sandpaper).
But this time, increase to the 320 grit type; then 400-grit and 600 grit.
Remember to wipe the surface thoroughly after all.
14. Waterbased Poly
Apply a thin layer. The best method is to adapt gently using a sweeping motion.
15. Let dry and cure
Can you put water-based poly over oil-based poly
16. Wiping
Buff out and wipe out any pieces of dust one more time.
Take a look from an angle to check the bright light shining on your surface now.
If you find any dust, wipe it again using the 1500 grit sandpaper or brown paper bag.
Finish the whole process with a piece of soft cloth to polish your surface in a small circular motion.
Yes, you now really can apply water-based polyurethane over oil based polyurethane!
The most important thing in apply water-based polyurethane over oil-based polyurethane is the Let dry and cure process.
The whole procedure requires a decent waiting time for each formula; and might take up to 10 hours waiting between each layer.
And keep in mind, there are some types of water-based that are not suitable for application over lacquer or shellac.
Do not abuse and apply as you wish.
Conclusion
There are some more tips for your process that you can take away for successful results
- You can make your polyurethane less thick by adding 10% mineral spirits
- Always remember to keep your surface and your working space totally clean of dust
- If possible, put on a lot of reflected lights to help you spot any dust or bubbles, or unevenness.
- Always keep in mind that each coating needs to be fully cured and dry. Otherwise, the two formulas will not be consistent with each other.
- Be patient. You really need to be patient with a lot of waiting between each step. If one step is not taken long enough, your next coating layer will not cure properly. And it will result in a permanent tacky finish.
- Depends on each surface and dimension, you can decide to use 2 or (even) 4 coating layers. And still, be patient with each layer you adapt, as always.
Required Materials
- Power buffer or sandpaper (150, 280, 320 grit)
- Mineral spirits
- Vacuum cleaner
- Respirator mask
- Your choice of water-based poly
- Brush to apply the poly
- Sandpaper of 1500 grit (and/or brown paper bag)
- Polishing pad
We just completed this question: “Can You Put Water Based Poly Over Oil Based Poly” and now, you know what exactly to do. Let’s practice that!
Further Reading:
- Best Finish For Hardwood Floors
- Best Wood Finish For Outdoors
- Top 5 Best Primer for Bare Wood
- Best Wood Stain Remover
- Building With Wet Pressure Treated Lumber
- Can You Use Pressure Treated Wood Indoors?
Tags: water based finish, floor finish
