Drying wood is necessary to remove excess moisture and make timber suitable for woodworking or burning. The most traditional method of drying wood is air drying, where you stack them up in piles and let them release water naturally. However, if you have an urgent project, you can speed up the process by drying your wood in a kiln. Even though using a kiln makes the process faster, people still question subsequent operations on kiln dried woods, like can you paint kiln dried wood immediately?
Yes, you can. Drying wood in a kiln removes 98% of moisture in the wood, making it an ideal surface for coating products. The low moisture content will also allow the paint to grip the wood better than most surfaces.
Additionally, since kiln drying uses a lot of heat, you won’t have to worry about subjecting your wood to harsh chemical treatments before coating it with paint because the high heat kills insects and their eggs and larvae.
Nonetheless, before painting kiln-dried wood, you must let the wood acclimate to the atmosphere of your workshop before painting it to avoid future problems.
What Does Kiln Dried Mean?
Kiln-dried is a term used to refer to wood that is dried in a kiln/oven instead of open air. Wood from a freshly cut tree contains high moisture content (MC), so it needs some time to lose the water and stabilize in size and grade for easy use.
You can stack the timber outside with spacers between them and allow the wood to release its moisture naturally. However, air drying is a slow process that can take between two months to a full year for the wood to achieve a moisture content that you can use for woodwork.
To hasten the process, wood millers dry the timber in a kiln to control the environment around the wood. With a kiln, you can adjust the temperature, humidity, and air circulation for a set period allowing you to reduce the MC of your wood to a target point much faster while avoiding the natural drying defects.
The kiln drying process requires up to 170°F to heat the air around the wood. Large fans then circulate the heated air all around the kiln to force out moisture rapidly while maintaining a consistent drying rate for all the timber.
Once the air gets saturated, inbuilt dehumidifiers in the kilns remove the moisture, and the cycle continues until the wood achieves the desired MC. Millers usually aim for MC between 6%-8% for wood meant for use indoors and 9%-14% for timber meant for exterior use.
Kiln drying may seem like a simple process of setting the oven conditions to a specific figure and waiting for the water content in wood to go down, but it is not.
Maintaining a specific temperature, airflow, and humidity levels only makes the process take longer. Instead, it is best to monitor the drying rate and alter the factors periodically to allow the wood to reach its EMC quicker and more efficiently.
Moreover, monitoring the drying rate will ensure that the outer edges of larger woods do not dry faster than their centers. If left unmonitored, the moisture imbalance will make the outer edges shrink, causing severe cracking and checking in the wood.
How Soon Can You Paint Kiln Dried Wood?
You can paint kiln-dried wood as soon as it achieves its Equilibrium Moisture Content (EMC) in the area where you intend to use it. After drying wood in a kiln, it will have the moisture content level you deemed workable.
However, upon exposure to the environment outside the kiln – during transportation, manufacturing, or installation – the lumber may reabsorb water or lose more moisture if the surroundings are too dry.
EMC defines the point where the wood stops absorbing or releasing water into the atmosphere in the woodworking industry. So why is it essential to wait for kiln-dried wood to achieve its EMC before painting?
Wood expands and contracts as it gains or releases moisture into the environment. The more moisture it absorbs or releases, the more extreme the wood product’s expansion or contraction.
For instance, say you were making a wooden kitchen cabinet or table in a work area where the average moisture content is 10%, indicating a humid environment. But, your lumber was acclimated to surroundings with a 5% average moisture content indicative of a drier environment. When you expose your wood to the “wet” environment, it will start to take in moisture and expand slightly.
If you color the wood in that state, the paint will chip, crack and peel off the surface. You will also experience the same devastating results when the moisture content levels are reversed, and you work in a drier environment. So, how do you find out if your wood has reached moisture equilibrium?
The first step is to let the wood sit in the installation environment for a few days, and during that time, check the % moisture content of the wood using a wood moisture meter.
Take readings every few hours until the reading on the meter stops changing; then, you can make your product and paint it. It may take your lumber a few days to fully adapt to its surroundings, depending on its moisture content after kiln drying and the temperature and relative humidity of the new environment.
The more significant the difference between the MC of the wood and its EMC point, the longer it will take to acclimate fully.
How Do You Tell If Wood Has Been Kiln Dried?
Several factors help distinguish between kiln-dried wood and air-dried wood, but telling the two apart will be hard if you don’t know what to seek. Both types of timber have a low enough moisture content that allows you to use them for projects.
However, since the two drying processes are so different, millers recommend using each type in specified areas to ensure the success of woodworking projects. Below are a few characteristics of kiln-dried wood to help you as you search for seasoned timber for your project:
- Consistent MC Across the Wood
Measuring the MC of your wood is the first step in identifying the method used to dry it. For kiln-dried logs, the reading on your moisture meter will show one figure throughout the wood. The figures contrast air-dried lumber which shows a higher MC in the core of the wood than the outer edges.
- The Wood Is Fragile.
Kiln-dried wood tends to break and chip more quickly than air-dried ones, especially when working with hand tools. During kiln drying, the outer edges of the wood get subjected to high temperatures that cause the fibers to dry below their saturation point.
They then shrink before the interior part is ready, causing complicated internal stresses that cause the wood to be brittle. Millers often have a way of conditioning wood after kiln-drying to get rid of the stresses, but in comparison to their air-dried counterparts, kiln-dried wood will still be more fragile.
- The Wood Looks “Faded.”
Kiln-dried timber can lose up to 20% of its color even without steaming. The extremely high temperature of the kiln kills some of the subtle hues in the wood grain, causing the wood to have faded brown color.
- The Wood Weighs Less.
Kiln drying sucks out most of the moisture in wood, leaving only about 6-10%. Because of the low moisture content, kiln-dried wood weighs less than air-dried and green timber. Due to their lightness, woodworkers prefer using kiln-dried wood to make furniture because they’ll be easy to move around.
Can You Paint Untreated Wood Right Away?
Untreated wood is timber still in its natural form, meaning that no harsh chemicals are added as a preservative. You can paint untreated wood, but I do not recommend doing so unless yours is from a species that can naturally ward off insects, fungi, and the effects of harsh weather.
Some of the best wood species you can paint while untreated include redwood, cedar, cypress, and teak wood.
If you must paint untreated wood, you need to pay special attention during surface preparation and when choosing coating products. This way, you will prevent moisture damage to the wood and prevent natural tannins from bleeding through your paint. The following is a step-by-step guide to help you paint untreated wood:
- Start by sanding the wood with rough 100-grit sandpaper. Since the wood is untreated, the rough sanding will help even out gouges on the surface and eliminate splinters. Vacuum away the sanding dust, then do some follow-up sanding using 150-grit sandpaper to make the surface smooth enough to produce even paint coverage. Vacuum away the dust again but this time, follow up with a clean, lint-free rag to remove any remaining dust that may interfere with paint grip.
- Next, use a brush or roller to apply exterior wood primer on the surface. Even if you intend to use your piece indoors, I recommend using an exterior primer because it seals the wood surface, thus blocking moisture from contacting the untreated surface and ruining it. Apply the primer against the wood grain to ensure the product better seals the surface. If you are working with species such as redwood, cedar, or maple, ensure that you use an exterior primer labeled “stain-blocking.” These wood species slowly release tannins that will bleed through standard primers and ruin your paint job. Not all woods release tannins but, if you do not know the type of wood you have, use a stain-blocking exterior primer from the start to be safe.
- Once the primer dries properly, apply an oil-based paint to the wood. I recommend using oil-based paint to color untreated wood because it is more durable; hence, it can withstand harsh environmental conditions and prevent damage to the vulnerable untreated wood. Furthermore, oil-based paints provide excellent coverage for surfaces, so you might not need a second coat.
What Happens If You Paint Wet Pressure Treated Wood?
Wood pressure treatment plants use a lot of water to introduce preservative chemicals deep into the wood fibers. Thus, the lumber will be very wet when it comes out of the treatment chamber, and it might take several months to dry enough for painting, depending on thickness and type of treatment.
Several months may seem like a long time, and if you are not patient enough, you will color the wood while it is still wet and experience devastating results.
So what happens if you paint wet pressure treated wood?
- The Paint Won’t Dry.
Painting pressure treated wood while wet is essentially locking moisture within the lumber. With nowhere to escape, the moisture will ooze through the paint, preventing it from drying properly.
Wet paint is an inconvenience because it is more likely to sustain damages than hardened paint. Furthermore, the color will not be what you expect because paint only produces its intended color when it dries.
- The Paint Will Peel
When you paint over wet treated wood, the moisture will not allow the coat to grip the wood fibers properly. Consequently, the paint will begin to flake sooner than if you had given the lumber enough time to dry.
Even after applying the paint, your wet wood will lose some moisture and shrink in the process. The slight change in size will accelerate the peeling of the paint even further, and soon, you will have to sand away all the product and start all over again.
- The Wood Will Warp
Peeling paint aside, the shrinking of painted wood will also cause it to warp, specifically when one side of the surface shrinks faster than the other.
When you color one side of the wood, the unpainted surface will dry and shrink faster than the painted side, and as a result, the painted side will begin to pull towards the bare side, causing the surface to warp.
Since painting wet pressure-treated wood has adverse effects, how can you tell if your pressure-treated wood is ready for painting?
The following are three tests that you should do in succession to ensure that your wood is dry enough to paint:
- The “feel” test – For this test, press your bare hand or a paper towel on the surface to see if you will detect any moisture. If you feel some dampness on your hand or the paper towel becomes moist, it means that the timber is still too wet and needs more time to dry.
If you don’t detect any moisture, it means that the wood is dry, but it does not mean that the surface is ready to paint. So follow up with the water test.
- The water test – Sprinkle several drops of water on a small area of the wood for the water test. If the droplets soak into the surface, it means that the wood is ready for painting. However, if they form beads, there is too much moisture within the wood, and you need to let it dry a little more.
Even though the water test produces conclusive results, you may not be able to tell if the whole plank is dry. And since dousing water on the whole surface would be unreasonable, the last resort would be to use a moisture meter.
- Using a digital moisture tester – The final and most accurate way to test the dryness level for wood is by using a digital moisture meter. These gadgets have two prongs to press into the wood to test its moisture level.
Make sure that you test more than one spot on the surface, then calculate the average of the figures you see to get an accurate moisture level. Also, ensure that you calibrate your device properly before using it to get precise measurements.
NOTE: If you are worried about waiting too long for pressure treated wood to dry, you can have your lumber kiln dried by the manufacturer after treatment to speed up the process.
The Video Below Show’s How to Prepare and Paint Furniture:
Drying wood is an essential process that makes timber suitable for woodworking projects and even burning. You can air-dry your wood, but it may take up to a year to achieve a workable moisture content. You can also dry it in a kiln to speed up the process for time-sensitive projects. Kiln drying is a process that allows you to regulate the atmosphere around the wood as you like to achieve the desired MC in as little as ten days. But the burning question remains…
Can You Paint Kiln Dried Wood Immediately?
You can paint kiln-dried wood immediately after it acclimates to the atmosphere of the surroundings where you intend to use it. When wood leaves the kiln, it still can lose and absorb moisture from its surroundings. Since the atmosphere in the kiln is different from the atmosphere in your workshop, it is crucial to let the timber sit in its new environment until it reaches its Equilibrium Moisture Content.
EMC is a term used to refer to the point where the wood no longer absorbs or releases water because its moisture content is at per with its surroundings. It may take your wood a few days to achieve its EMC and, the best tool you can use to get accurate moisture readings is a digital moisture meter.