The Pros and Cons of Water Popping

Hardwood Flooring with a ViewHomeowners 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

Hardwood Floor in ApartmentA 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.

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

Hardwood FlooringIf 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 Stain Appears Darker and Richer

Hardwood FloorPerhaps 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, higher the humidity, or less air circulating, the greater amount of time you need for drying.

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.

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.

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Tony Morgan

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.

25 Comments

  1. Brian Nguyen says:

    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

  2. Nikki W says:

    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!

    • Tony Morgan says:

      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!

  3. Tony says:

    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

  4. Josh says:

    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

  5. kent hudson middlemass says:

    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

  6. Dana Maguire says:

    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.

    • Tony Morgan says:

      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.

  7. Astral says:

    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

    • Tony Morgan says:

      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

  8. Astral says:

    Sorry forgot to add, I had hard bottom slippers on

  9. fran says:

    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…..

    • Tony Morgan says:

      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.

  10. Gwen says:

    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?

    • Tony Morgan says:

      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.

  11. Fixerupper says:

    Hi
    Can alcohol be used for water popping?

    • Tony Morgan says:

      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.

  12. David Pena says:

    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!

    • Tony Morgan says:

      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.

  13. Antonio Pereira says:

    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.

    • Tony Morgan says:

      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.

  14. David says:

    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!

    • Tony Morgan says:

      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.

  15. David says:

    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

    • Tony Morgan says:

      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).

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