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The Pros and Cons of Water Popping
Homeowners and commercial real estate developers love wood’s long-lasting beauty. Wood blends in with most types of décor and is easy to clean and maintain.
It’s environmentally safe, does not trap dust mites that can affect your indoor air quality, and it is comparable in price to other types of flooring such as stone, tile, and quality carpet.
However, the natural structure of wood – which looks appealing on the outside – is also what can cause problems from the inside. It all has to do with the relationship between wood and moisture. This is why water popping is such a vital, yet risky task when installing wood flooring.
What Is Water Popping?
Also called “grain popping” or “raising the grain”, water popping is a process that opens the grain in wood flooring; it involves adding water to the wood before you stain and finish it.
The Science Underlying Wood and Moisture
Wood is a hygroscopic material; it contains numerous cells that absorb water. In the tree, these cells fit together in groups of thin vertical passages like pipes. The cell wall contains a small amount of moisture, whereas the “hollow” part of the inner cell has room to hold and release moisture. The purpose of these cells and pipes is to collect and transfer water and nutrients from the roots of the tree to other parts.
After a tree is cut down, the green lumber is very moist, so the lumber must be kiln-dried to remove the excess moisture and make it ready for manufacturing.
However, the structure of the cells in the wood remains the same as before the tree was cut. Even long after cutting the tree, the cells in the wood absorb and release moisture from the environment. This moisture can be from relative humidity in the air, groundwater or water leaking from faulty plumbing.
As the humidity in a room goes up or down, the wood absorbs or releases moisture. This is a continuous exchange, even after you finish your flooring project.
Wood Moisture and Why You Need Water Popping
A wood flooring manufacturer buys kiln-dried lumber and cuts it down to size. Then, the lumber must be sanded down – often through several passes. During this process, the hardwood goes from being coarse to becoming fine and extremely smooth.
The sanding process closes the natural grain of the wood so the wood is no longer porous enough to accept stain. That’s because the tiny wood particles and sawdust get stuck inside some of the pores.
The sanding process begins with a coarse, low grit paper to flatten and clean the wood, then progressively finer grit sandpaper is applied to smooth the surface even more. Finer grits tighten the grain fibers, making the wood denser and less porous and penetrable.
The result is that the stain is not absorbed deeply into the wood, and most of the stain will be removed when wiped with a cloth.
Test your wood flooring with the most accurate and reliable wood moisture meter.
Benefits of Water Popping
When water is added to the wood before staining it reopens the pores in the grain. It makes hardwood floors porous again so that hardwood flooring can be properly stained and finished.
This process has many benefits.
- It allows the stain to be applied more evenly across the floor
- It raises the wood fibers so the stain goes deep into the wood for a nice finish
- It helps create a professional look and feel without any sanding marks
- It makes the color stand out
It is important to use a precise quantity of water. Too much water can oversaturate the wood. This can cause the wood to swell in the short term. In the long term – as humidity decreases – the wood will release the excess moisture.
In addition, care must be taken to spread the water evenly across the surface of the floor. Uneven water distribution can cause your floor to show blotchy areas under the stain. If this happens, the only remedy is to re-sand the surface of the wood, which costs time and money.
To reduce this risk, many flooring professionals use a “T” bar. A “T” bar is shaped like a broom with a long handle that meets the end piece at a 90-degree angle. The end piece contains a straight-edged piece of rubber, like a window squeegee, that touches the floor and helps you distribute the water evenly.
Some use chemical sprayers to mist the floor with water. Some use a buffer with a soaked carpet pad. Still, others run a wet mop over the floor. Perhaps the most effective way, though time-consuming, is a bucket, a rag and getting down on your hands and knees.
No matter which method, it is fairly easy to do. This is especially true if you have experience with applying water-based finishes. The difference is that water popping employs clean water without chemicals, whereas finishes often contain substances that can hurt the wood.
It’s best to use purified or sterile water, not tap water. Tap water can contain excess chlorine and other chemicals that can react with the wood or the stain.
A standard plant watering can be used. Pour a 2-inch line of water, with the direction of the flooring grain. Then use the T-bar to even out the water.
After coating the whole floor, no matter which method you choose, let it stand and dry on its own for between two to four hours. At that point, the floor should be somewhat gritty, with it no longer having a smooth touch to it. This is the effect of the grain in the wood reopening.
Perhaps the most important step in the process is the close examination of the whole floor. You need to make sure the surface of the floor feels the same throughout. An area that is rougher or smoother than other areas may indicate that you did not apply the water uniformly.
Two Choices for One Outcome
If the surface of the floor is consistent, then the process was successful and stain can be applied.
However, if the floor surface feels different in spots, then it is necessary to repeat the process, or more likely re-sand the floor. Remember, if re-sanding is required, the water popping process is necessary afterward.
A Deeper Look at the Benefits
Stain More Evenly Across the Floor
Due to the application of various grits when sanding, the grain throughout the floor may not be uniform. When water popping is done correctly, the pores are opened throughout the flooring, allowing the stain to be more evenly applied.
Raises Wood Fibers Promoting Stain Penetration
Water popping causes the fiber in the wood to stand up, providing greater surface area for the stain to absorb and penetrate deep into the wood. Applying two coats of stain can give you an even nicer look.
Sustain a Professional Look and Feel without Any Sanding Marks
Even the best professionals can make a mistake. Sanding wood flooring can leave marks, however small, that are noticeable until after the wood is stained. When the grain is raised from water popping, any sanding marks blend in with the wood fibers, and when stained the marks won’t stand out.
The Wood Floor Stain Appears Darker and Richer
Perhaps the thing that stands out the most on a wood floor is the deep rich color. Water popping enables you to make your stain appear darker and richer. Darker and richer floors are noticeable, which many people admire. Be sure to ask to see the color you select on a sample of water-popped wood. Otherwise, the color you are shown you may not be what ends up on your floor.
Risks
Uneven Water
If you pour uneven amounts of water on different sections of the floor, you increase your risk of the wood absorbing various quantities of moisture. This can cause your floors to break down in the near or distant future, and your stain will look blotchy afterward.
Staining before the Floor is Dry
If you do not allow enough time for the floor to dry before staining the wood, you run the risk of the stain appearing blotchy. Drying time can differ by temperature, humidity and air circulation in the room. The lower the temperature, the higher the humidity, or less air circulating, the greater the amount of time you need for drying.
Free Download – Wood Flooring Installation: What To Expect
Sensitivity to Scuff Marks
Once the wood has absorbed water it becomes soft and more susceptible to scuff marks. For this reason, you should not walk on the floor with any type of hard shoe or boot between the time of water popping and completing the staining process. Instead, wear only socks or slippers with very soft bottoms.
The Outcome Varies by Wood Type
The outcome from water popping can be incredible. You can have a professional floor that will last a lifetime. Visitors will commend you for a good job.
Nonetheless, your outcome can differ not only from the actual process but also by the type of wood. Each type of wood can differ in the amount of water needed for popping and the length of time to dry. Different types of wood also vary in how the color of the stain appears. These are the reasons why you ought to sample a piece of wood to “water pop” before committing to buying and installing the whole floor.
Test your wood flooring with the most accurate and reliable wood moisture meter.
What You Need Now – Moisture Measurement
Anyone can do it, but not everyone will do it right. To avoid the risks and maximize the benefits from water popping, it’s best to hire professionals who know how to measure moisture in the wood.
By looking at relative humidity at various places throughout the floor, you can get an accurate glimpse of how the moisture levels in the environment – now and later on – will affect the wood.
When the wood contains a low level of moisture that is at equilibrium with the environment and uniform throughout the floor, you can then seal it and apply the stain. An accurate wood moisture meter can help you lower or prevent the risks from water popping.
Tony Morgan is a senior technician for Wagner Meters, where he serves on a team for product testing, development, and also customer service and training for moisture measurement products. Along with 19 years field experience for a number of electronics companies, Tony holds a B.A. in Management and his AAS in Electronics Technology.
Last updated on June 30th, 2021
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Hi Tony,
Reading your blog has answered most of my questions. I am refurbishing my oak hardwood floor. I replaced many slats with salvaged hardwood (which I now know was a stupid idea), so I had to use a lot of bondo to fill in gaps between boards and to fill nail holes.
Is water popping recommended when there is a lot of bondo (wood filler) on the floor?
Thanks in advance,
Cyd
The science around water popping is to open up the pores in the wood to allow for the stain to penetrate. Bondo is non-porous, so if you were to water pop the floor, you would end up with noticeable areas where the stain would not penetrate.
Thanks!
Can you water pop a floor if you are not staining it just putting 3 coat of clear polyurethane on it ?
Kevin:
Great question. I would recommend either talking directly with the polyurethane manufacturer and/or talking with the National Wood Flooring Association at nwfa.org. Good luck.
I use water-popping to open maple pores on violins I make. I wipe down the flamed maple with a damp microfiber cloth. Then, I stain it.
Hi Tony,
I have maple level 2 floors 3″. Original stain was orangey yellow. Added new hardwood to two rooms and tied into existing wood in hallway. I originally wanted just natural with clear poly, but opted for stain because of fear the tie-in areas would look better with stain. No one told us that it’s not recommended to stain maple 🙁
Flooring company sanded everything, water popped and applied Early American minwax stain and three coats of water poly. Color looks blotchy, milky or cloudy in spots and just terribly uneven. The stairs look like I tried to sand the color off and got half way through the job (like a cheetah print). There were also several craftsmanship problems: footprints, drips, edges were darker, big dark circle where they started applying the stain on the machine, big sweeping “lanes” of very different coloring, wavy hallway, etc.
Flooring company came back and sanded everything down again. For the most part it looks beautiful as-is, with a few spots where I can still see remnants of the stain, but you really have to look for it. I am fearful of trying stain again and we’ll just end up with the same blotchy brown floor. I do really like the natural color, but also not sure what the poly will do. Will it make it look yellow? They are using water-poly and I hear that won’t be yellow. But again I’m just not sure this crew has enough experience with maple (they mostly work on oak).
Thoughts? Anything that should concern me if I stick with just a clear coat? Thank you so much for any advice you can give!!
Hi Tony, I am on my first project and just water popped the wood. Its a very heavy door (light-ish blond with black grains throughout ) This house was well built in the early 1900’s and has a lot of architectural wood detail. My question is should I sand over grain by hand when door dries or with the electric circular sander? My last pass was 180 grit. I’m using a water based polyurethane and going for a raw wood look. Also, does it matter how much time passes in-between water popping, sanding and finishing coat?
Thank you.
Thank you for your question. Water popping a door should be very similar to doing a floor. Generally, a circular sander is used for flooring because hand sanding would take much too long. Generally, a stain is applied 1-4 hours after the water popping is done and then at least three coats of polyurethane are applied when the stain has dried.
I have laminate flooring it was here when we bought the house. The house is on a slab. Our floor is pulling a part there are places 1/4 how can we push those back? This flooring is no longer available and we don’t have any spare boards to replace it with. We have been told it is because of moisture from bein on a slab. This is a condo so you can’t get under to look at it. Thank you for any information.
The most likely cause of this may have been that the flooring was installed when it had too much moisture in it, or, the concrete slab was too wet when the flooring was laid. These conditions would cause abnormal gaps (over 1/32nd to 1/16th in width). Due to it being a laminate to correct the gaps in this floor it may be necessary to replace the floor.
If it were a solid wood floor, after stabilizing, this condition could possibly be corrected by using filler in the smaller gaps and slivers of wood for the larger gaps, then the entire floor would be sanded and recoated.
we just added on to the house. I got a new kitchen the new floor is laminate. {The instrustion said no water just dust mopp. But that is stupid for the kitchen. So, will Basic H work on my floor ?
Engineered wood floors need much the same care as solid wood floors but it should be safe to mop them as long as great care is used to avoid letting too much water sit on the floor.
1. Always sweep or dust mop your floor before washing to prevent grit from scratching your floor.
2. Never use waxed based, or harsh chemicals on your floor and do not use abrasive materials such as steel wool as these will damage or scratch your floor.
3. Use a flat-bottomed mop as opposed to a string type to avoid the risk of water accumulating on your floor.
Hi Tony
I recently had a solid hardwood american cherry floor put down in my home over the summer/fall. This winter the furnace was bumped up to 75 degrees by a well meaning house sitter when the temperature dropped to 3 degrees. I came home to a floor that had shruken and had large gaps and the boards were twisted and sticking up on the sides. I have been running a humidifer at 45% which has allowed the floor go back to its natural shape considerably. But there are still a few planks were there are some gaps. I am wonder if I could “water pop” these gaps. I was wondering if i applied a very very small amount of distilled water to these gaps ( which are the planks where there is no stain, so they would not be sealed) would it open up the pours of those boards and allow those remaining gaps to close? .
Thoughts?
The problem with putting water on some of the boards is that it may discolor them. A moisture meter, such as the Wagner MMC205, would be very helpful to check the boards that still have gaps and compare them to boards that are looking normal. This would tell you if there is a difference in the boards’ moisture content and that more time may be necessary for some boards to reach equilibrium. If this is the case, give the humidifier some more time. If it does not correct the problem, you may have to try other methods, with board replacement being a possible final answer.
For narrow gaps, putty, powdered filler which is mixed to a putty or paste form, or even caulking is a remedy you can try as a homeowner.
If the gaps are wider, wood shims or narrow strips of wood may be necessary to fix them. This process is a little more time consuming but is a more permanent and is often more attractive looking than using a putty or paste. The final solution may be replacing individual boards to correct the gapping issues. If any of these two scenarios seem to be the best answer, I recommend contacting a reputable flooring installer and have them look at the issue. They will best be able to give advice or correct the problem.
You should be able to find a certified flooring professional in your area at: https://www.woodfloors.org/certified-professional-search.aspx
Hi Tony
I have recently purchased an older home with untreated pine floor boards in one of the rooms. The boards had been covered with loose vinyl which was easily rolled up. It appears that the owners had pets in this room as the urine stench was quite horrific.
In order to try and get rid of the odour, I liberally sprinkled the entire floor with carb soda and then also liberally, sprayed neat white vinegar. This was left for the rest of the day and overnight. The next day the dried carb soda was swept up, the floor carefully vacuumed including all joins and cracks and the process repeated three times over a period of a week…yes, the smell was that bad and each time there was an improvement.
My issue now is, that although the odour is now negligible and the floor is completely dry throughout the day, by next morning the floor is completely covered in moisture as if it has leached out of the floor boards overnight. The room is well ventilated with good air flow and the new excess moisture is gone within an hour. To add to the mystery, this leaching does not appear to happen each and every morning. It might go a few mornings remaining dry, and then the moisture reappears.
The boards are suspended a good metre off the ground and the ground under the entire house is bone dry.
Could you please give me an idea of:-
Why this is happening?
How long this might continue to happen?
What else can I do to help fix the problem?
When will the floor be suitable to sand and then seal?
Thank you in advance for your advice. Cheers.
Sue,
Since wood is a hygroscopic material, it absorbs and releases moisture, so in saturating the floor it has acted like a sponge. The solution you used is probably still leaching out so my best recommendation is to use a moisture meter to monitor the floors’ moisture content (MC) until it reaches a point where sanding and refinishing can be done. I would also monitor the relative humidity (RH) and temperature as well. This will help you in calculating the equilibrium moisture content (EMC) for the floor. This the point where the MC of the floor is at the same level as the environment.
https://www.wagnermeters.com/time-temperature-and-relative-humidity-the-variables-of-emc/
HI Tony, I have red oak floors we sanded three cuts and I want to water pop them. After I water pop and stain which sand paper to you use on the buffer machine? can if be wet sanded? I read that it is good to wet sand as there is less dust. Thanks
Normally all sanding is done prior to staining. After staining, sanding is almost never done as it can cause marks that are noticeable on the finished floor. Give the floor time smooth itself down after staining. Usually 3-5 coats of poly will cover any rough spots after the floor has been stained.
If you believe sanding is necessary, first test an area that will not be too noticeable if there is a problem. Try using a super fine grit ~ 320 on the test area to see if the stain color remains true. Remember the only true way to fix a mistake after water popping is to start the whole process over and re-sand the entire floor. You do not want to wet sand as the water can cause problems if left to soak into the flooring.
Dear Tony Morgan,
Is Water Popping just for floors to be refinished with water-based stain?
You can finish with either an oil or water-based stain, but with an oil based stain, you have to take into account a longer drying time than with a water-based stain. After water popping always allows sufficient time for the floor to dry thoroughly before applying any stain and take into account the weather and humidity.
Hi Tony
Is the correct process to sand, water pop then stain? Or, do you recommend popping and buffing and repeating until the grain doesn’t raise anymore? You mention it a couple times both ways so looking for clarification. Great blog, appreciate it!
Dave
The actual process for doing “Water Popping”, involves sanding, water pop, stain, then possibly sanding again to smooth any excessive roughness before doing any poly coats (if applicable to the job).
Hi Tony,
I just had my maple floors sanded and stained, but not yet sealed. I wasn’t told by the person doing the job, nor did I know, that maple floors don’t take stain very well. It’s very blotchy and the sanding marks are very visible throughout, especially 8″ from every wall, and I’m very disappointed in how it looks. Is there anything you would recommend before sealing it? I’m thinking about asking if we can have some sort of dye finish applied before sealing but would love your advice as you seem to have far more experience with this than the person I hired. Thanks in advance!
Hello David,
The tight grain of species such as maple, cherry, and birch make them take stain in a blotchy fashion.
Water popping, if done correctly, would help minimize the blotchiness by opening the pores to accept stain more evenly.
Another method to minimize the blotchiness is to use a wood conditioner, also known as “stain controller,” before applying the stain. The conditioner fills in the largest pores of the wood, resulting in a more even appearance.
Also, it may be the contractor did not finish with a fine enough grit sandpaper. Sanding wood flooring can leave marks, however small, that are noticeable until after the wood is stained. When the grain is raised from water popping, any sanding marks blend in with the wood fibers, and when stained the marks won’t stand out.
Unfortunately, in order to do either of these methods, you would have to start the job over from scratch.
I just laid 500 sq. ft. of 12″ wide antique red oak flooring. I want to give the floor a wire brush finish to pull out all the grain. Can I water pop after the wire brushing and then apply my stain? Or should I forgo the water popping, since it has been wire brushed and go straight to stain.
Hello Antonio,
The purpose of water popping is to re-open the pores of the wood, in addition to raising the grain, so that stain can penetrate deeply into the wood for a nice finish.
In order to accomplish this, you would need to do the water popping after you wire brush the floor.
I had this procedure done in my home. The job was finished about 7 days ago. The floor looks and feel grainy…
I was told that it would go away in 2 to 3 weeks and that the results would be an smooth surface!
What do you think?
Please advised!
Hello David,
One of the side effects of water popping is grain raise. Usually a buffer is run over the floor after it dries but before it is stained in order to smooth the raised grain down. Please ensure this was done but also give the floor the 2-3 weeks to make sure that it has had time to equalize.
Another question to ask is if the installer used a moisture meter to make sure the floor had dried out evenly before the the finish was applied.
Hi
Can alcohol be used for water popping?
There are a few flooring companies that do use a denatured alcohol and water mixture for water popping, it is usually used in a 50/50 mixture and sprayed onto the floor with a pump sprayer. This is to diminish the drying time.
What is the type of wood in the first photo above right under the words, “The Pros and Cons of Water Popping” and the stain color and stain manufacturer?
Hi Gwen,
The photo in question is not one that we personally took so we do not have information regarding the stain color and manufacturer. I would suggest that you print a copy of the photo from the site and take it a professional flooring expert or store that specializes in stains and paints to get their advice.
I just ran into the same situation. My floors were water popped about 2 1/2 hours ago and had no choice but to enter my house to try to turn off a smoke detector that wouldn’t go off! I took my shoes off and walked through the house to open up some windows to try to reseet the thing to no avail. Do I need to b concerned? I tip toed through there…..
Hi Fran,
There is a chance, given you walked on it, that damage was done to the floor. If there are any doubts, it would be best to start over to ensure no damage was done.
Sorry forgot to add, I had hard bottom slippers on
So we have been doing our floors and I walked on them after the water popping process, what do you think the out come will be in those spots where I walked? I didn’t know I should walk with socks, husband told everyone but me
It would really depend on how soon after the water popping was done. There is a chance, given you were in hard-soled slippers, that damage was done to the floor. If there are any doubts, it would be best to start over to ensure no damage was done.
Thanks,
Tony
Hi There,
I am building hand drums that are constructed entirely out of wood. The playing surface is 1/8″ Baltic Birch. The body of the drums is usually a hardwood such as Black Walnut, Black Locust, Maple, Ash, Oak, Cherry. I also use some soft wood such as pine and I am considering cedar. I am curious about water popping in this situation. I do like the idea of being able to go a little finer with the sanding and bring grain back to accept the oil. I just purchased some Rubio Monocoat 2C. It will be my first time using this product. I would not say I am an expert in the finishing department.
Water popping is usually done before using a water-based finish. The purpose of water popping is to raise the grain by swelling the wood fibers and opening of the pores in the wood. After the water evaporates, the fibers stay in the swelled position and the cleared pores take stain much more evenly. This makes the grain pop out and become more visually appealing after the finish is applied.
It is recommended to use distilled water, as it doesn’t have any minerals that can discolor some kinds of wood. Don’t flood the surface, but wipe it on with a clean cloth and allow it to dry fully. Scrape or sand (very fine ~320 grit) away the raised grain gently, then repeat as necessary until the wood remains smooth after wiping on water.
Water popping was a old furniture technique I have been doing hardwood floors for over 30 years and water popping is a recipe for diasater I have done them and honestly not enough gain for risk just get a good quality floor stain instead
I’m no genius but once you seal the floor it won’t take stain. Once moisture is equilibrium with that of the house. you then can seal it and apply the stain
Hey Tony
Just wanted to add another option for water popping. I use Wagner stain sprayer it allowes you to very easily control the amount your applying. After switiching to the sprayer boards delamanating have became vituraly nonexistent, which is a real problem with mopping water on. Not only that the floor dries in a fraction of the time just my 2 cents
I just had my hardwood floors refinished. It took the workers a week to do 3 small rooms & cost me a lot of money. When they began to apply finish to floors, I noticed a LOT of blotchy patches as mentioned in your blog. So they applied MORE stain in between coats of finish two separate times. I don’t feel this was the answer. After reading your article, I believe that they did not give the floors enough drying time after “water popping” They literally water popped the floors, then went directly over them with the stain, maybe 20 mins later. Can you tell me if you think this is why my floors turned out with spots that appear BARE? Thanks for your time & for the pleasure of reading your article!
Hi Nikki,
There are a few conditions that must be met in order to be successful when water popping a hardwood floor:
1. Before doing the procedure, test a sample area and/or do a test board. This will determine the amount of water needed to successfully do a water popping. Also, using a moisture meter, establish a baseline moisture content for the sample and after applying moisture find out how long it takes for the flooring to return to the original moisture content.
2. Ask for a sample of your stain color choice on a water popped and a non-water popped wood sample, this will give you an idea of what the finished floor should look like.
3. Record the moisture content before water popping. The flooring must be allowed to dry before the finish application.
4. After a floor is water popped, and before a stain is applied, it is extremely delicate. Any scuff marks left from a misplaced shoe movement will result in a lighter area on the floor and be cause for a complete re-sanding of the entire floor.
As mentioned in the article, “In addition, care must be taken to spread the water evenly across the surface of the floor. Uneven water distribution can cause your floor to show blotchy areas under the stain. If this happens, the only remedy is to re-sand the surface of the wood, which costs time and money.”
Hope this helps!
Dear Mr. Tony Morgan
I am installator wood flooring at Vietnam. So after i read the thread about popping water, can u help me support my question?
Now i install 01 project with phesant solid wood floor. After i sanding, apply primer, waterborne coating finishes ==> the surface has raising grain ==> can you help me how can i solve this problem? My method installation glue down, i use titebond glue., Bona mix and fill, Bona primer classic, Bona mega waterborne finishes. Thank you so much your support.
Brian Nguyen