Wood stains are an easy way to enhance the texture of grain. And a penetrating oil-based stain will give wood a durable coat of fantastic color.
Now, stains typically take around 12-24 hours to dry. But what if, after days have passed, that stain is still fairly sticky? Can you seal it with polyurethane regardless?
Well, in this post you’ll find out the three main reasons why tacky wood stain struggles to dry properly. You will also learn why polyurethane won’t adhere to a tacky stained surface.
And keep reading to discover what you can do to fix sticky stain.
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Can You Apply Polyurethane Over A Tacky Stain?
In short? No you can’t.
You see, penetrating oil-based wood stains contain (for the most part) two key ingredients — binders and pigments. And they also include fast-drying thinners (to help thin stains out and speed up drying).
Now, the binding ingredient differs by brand. Some stains use a varnish binder. While others use polyurethane, (or even Linseed oil), as binders instead.
Nonetheless, one thing that all of those binding ingredients share, is the reason why they’re added to stain. Their main purpose is to bind pigment color to wood fibers.
However, in order to do this, binders need time to dry and cure. If they don’t, you’ll be left with tacky stain on the surface of wood.
OK. But Why Won’t Polyurethane Specifically Stick To Tacky Stain Regardless?
For the same reason why polyurethane doesn’t stick to any wood finish that isn’t wholly cured.
Polyurethane needs a clean uncontaminated surface to adhere to. If there are any oils or resins on the surface, polyurethane won’t dry and cure properly — at best.
At worst, polyurethane will ultimately flake and peel off later on.
So this is the main reason why you don’t put polyurethane on that tacky wood stain.
Instead, you need to fix tacky stain first. After which, you can seal it with the polyurethane finish of your choice.
So Why Is This Wood Stain So Tacky? Why Won’t It Dry?
Typically, one of the three following reasons commonly prevent wood stains from drying:
1). It’s Too Cold
Wood stains need at least a bit of heat around in order to dry. If the area is too cold, (i.e. below room temperature), this will obviously lead to wood stain taking longer to dry.
2). There’s Too Much Of It
This is usually the most common reason. Any over-application of wood stain makes it really difficult for it to dry fast.
This can happen when you haven’t rubbed the stain right down into that wooden surface. Or if you haven’t wiped away any excess stain.
3). There’s Too Much Humidity
Last but not least, if the environment is very humid, the moisture in the air will make it difficult for wood stain to dry quickly.
In fact, if relative humidity (RH) is 85% or more, then wood stains simply won’t dry at all.
Now, that’s the bad news. However, the good news is that you can easily use a dehumidifier to maintain a 45% RH to 55% RH ideal humidity range.
How Long After Staining Can I Go Ahead And Apply Poly Over It? Check your particular brand of wood stain first for instructions. However, as a general rule of thumb, wood stains should be dry enough to seal within a day.
I’ve Managed The Temperature And Humidity, And It’s Still Not Working! What Can I Do?
At this point, your next step is to try and thin out the wood stain.
Wiping stain down with a lint-free rag — soaked in Mineral Spirits — will soften and thin out tacky wood stain.
This will make it easy for you to remove any excess wood stain that may be preventing it from drying.
Quick Step-By-Step Guide To Thinning Out Tacky Wood Stain
Step 1: Put on some protective gloves.
You are going to be dipping your hands into a solvent, so let’s stay safe.
Step 2: Soak a rag (ideally a lint-free rag) into Mineral Spirits.
Step 3: Run the soaked rag over the tacky wood stain.
Afterwards, wait for 2-3 minutes.
The mineral spirits solvents will soften up that too-thick wood stain.
Step 4: Using a putty scrape (NEVER fine steel wire wool) remove as much of the tacky stain as you can.
And, you only need to get rid of the excess congealed stain on the surface.
Step 5: Get another separate fresh clean lint-free rag, and soak it in Mineral Spirits.
Squeeze off as much of the excess mineral spirit so that the rag is left damp, rather than soaked through.
Step 6: Run the damp rag over the surface.
Remove the last of any tacky stain left behind.
Related Post: Can You Use Mineral Spirits Before Wood Stain?
Great! Once That’s Done Does A Wood Stained Surface Always Need Sanding Before Polyurethane?
It will. This is best practice when applying polyurethane in general, because poly finishes need a bit of grit to adhere too.
Lightly sanding with 120-grit sandpaper will create enough grip for a polyurethane top coat.
And make sure you wipe down the surface with a clean lint-free (and damp with water) rag afterward. This will remove any oils, dust, or dirt from the surface, before you coat on polyurethane.
To Wrap Up, Here Are The 3 Key Takeaways From This Post…
- 1). Polyurethane needs to be coated onto a dry clean uncontaminated surface. Otherwise, it will flake and peel off.
- 2). If a wood stain is still tacky, that means that it is not wholly dry, and can often still leech oils and resins as a result. So, polyurethane will not stick and stay if applied over tacky wood stain.
- 3). Wood stains can remain tacky due to high humidity environments, or due to over-application.
Arminger, Benjamin, et al. “On the drying behavior of natural oils used for solid wood finishing.” Progress in Organic Coatings 148 (2020): 105831.