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In this article, you will learn about stain and poly. We’ll define each product, and tell you how long to wait after applying stain to follow with a coat of poly. Then, we’ll explain the factors that affect the dry time of stain, before reviewing how to mix and match water and oil-based products.
What Is Stain?
Wood stain is a liquid used to change the surface color of wood. It can be transparent or close to opaque. Dyes or pigments are mixed with a liquid, called the ‘vehicle’. The vehicle could be oil or a mix of water, solvents, and acrylic resin. Binders are often added to help the stain adhere to the wood.
Stain is simply to apply to wood. You can brush it on, or for larger projects, use a sprayer.
Stain changes the color of the wood. It does not protect it. Therefore, it is often covered with a clear, film-forming finish that repels water and prevents impact damage. Polyurethane is a popular choice for covering stained wood.
Read more about our top choice for stainable wood filler.
What Is Poly?
Poly, short for polyurethane, is a kind of varnish used to protect and finish wood. It can be brushed, rolled, sprayed, or wiped on. It is a buildable finish that dries to a hard, durable protective barrier.
Polyurethane is a film-forming finish, which means the barrier sits on top of the surface of the wood rather than seeping into the pores.
Polyurethane is one of the most durable wood finishes available, while also providing excellent protection from moisture. It hardens through a two part process.
- First, the solvents evaporate, leaving it dry to the touch.
- Then, the molecules rearrange themselves more closely together as they are exposed to oxygen, creating an extremely hard finish.
When fully cured, it is food safe and difficult to scuff, scratch, or dent. Polyurethane is used when wood needs heavy-duty protection.
Applying Polyurethane After Staining – How Long Should I Wait?
Rule number one of applying polyurethane on top of stain is to check the labels of both products. While there are general guidelines, every formulation is slightly different, and following the manufacturer’s instructions will usually give you the best results.
- As a general rule of thumb, wait 72 hours after your final coat of stain before applying polyurethane.
- 24 hours is the minimum amount of time you should wait before covering stained wood with polyurethane.
- A 48 hour window between stain and polyurethane is a good middle ground.
The danger of applying the polyurethane too early is that the stain and polyurethane will mix. This can result in uneven colors, a blotchy appearance, and poly that takes a long time to dry or doesn’t dry at all. The polyurethane may not properly bond to the wood surface if applied over stain that is not fully dry.
Factors That Affect Dry Time
For best results, wait 72 hours between your last coat of stain and your first coat of poly. In most circumstances, this will be plenty of time to ensure the stain has fully dried. However, there are a few additional factors to keep in mind.
First, the brand of stain affects it’s dry time. The atmospheric conditions also affect dry time, so you should monitor the ambient temperature in your workspace. Keeping track of the humidity is also important when ensuring stain adequately dries.
To speed dry time, consider increasing the circulation of air in the area where the stained wood is drying.
If you need to finish a project quickly, look for a stain that advertises a quick dry time. The range of dry times for stain under normal atmospheric conditions is between six and 24 hours.
Room temperature, or about 70-75 degrees Fahrenheit, is ideal for drying stain. The manufacturer’s instructions assume you are applying stain under ideal conditions.
You can apply stain in colder weather, down to about 50 degrees Fahrenheit, or hotter weather, up to about 90 degrees Fahrenheit. However, the further away from ideal temperatures you get, the longer your stain will take to dry.
When the temperature is below 50 or above 90, it is not a good idea to stain wood. If you can, bring your project into a climate-controlled environment, or simply wait for better weather.
Humidity refers to the moisture content of the air. When the air is already moist, it is more difficult for the solvents in the stain to evaporate, and this slows the dry time significantly. In very humid weather, you may have to wait twice as long as the product label advertised before you can apply polyurethane.
By the same token, an extremely dry environment will encourage stain to dry more quickly. Running a dehumidifier in your workspace on humid days is an effective way to combat slow dry times.
Air moving over the surface of the stain will help it to dry, allowing you to follow up with a coat of polyurethane in the smallest possible amount of time.
Opening the windows helps if you’re staining indoors. You can also set up a fan (or multiple fans) to blow across the work surface. Dust or insects may stick to the stain while it dries. You can carefully sand the surface with very fine grain sandpaper to remove debris without removing the color.
What Polyurethane to Apply Over Stain
Theoretically, it is possible to apply water-based poly over oil-based stain. To do so, you must ensure that the oil-based stain is completely dry. Wait at least 72 hours.
In practice, this works best when you choose a polyurethane and stain from the same brand
Applying an oil-based stain over a water-based poly is faster — you only need to wait 24 hours for the stain to dry.
Choose a quick-drying stain and wait at least 24 hours to apply polyurethane for the fastest results. Controlling temperature, humidity, and circulation will give you the best drying conditions. Make sure the polyurethane and stain are compatible to ensure long-lasting coverage.