Prevent Lumber Loss in Kiln-Drying Operations With the Lumber Stack Probe

Have you ever removed a load of lumber from the kiln only to realize it’s still too wet? It forces you to stop, re-sticker (if the wood already went through the breakdown hoist), and load it back in the kiln. That’s like doing your job twice.

Talk about time and labor costs you can’t recoup!

Kiln-drying operations walk a fine line between overdrying and underdrying. Extremes or unevenness in moisture content can lead to wasted resources, production bottlenecks, wood damage, degrade, and even lost contracts. And that all adds up to lost revenue.

But lumber stack probe sensors can revolutionize your kiln-drying operations. So let’s look at all the ways they can help you boost your overall efficiency and limit damaged loads.

• The Evolution of Lumber Moisture Testing
• What a Lumber Stack Probe Is and How It Works
• Advantages of Using Them
• Kiln-Drying Operation Success Stories
• How to Make Your Own Success Story

By the end, you’ll have a clear path to keep your operations running smoothly and avoid losing profit.

To properly set the stage, let’s start with a quick overview of how lumber moisture testing methods got to where they are today.

The Evolution of Lumber Moisture Testing

In the past, the only way to measure moisture content (MC) in a stack of lumber was with a pin meter. But it came with drawbacks:

• Every moisture measurement left two pin holes in the lumber, which, of course, is a problem for some finished products.
• It was difficult to get the pins deep into dense wood without breaking them off.
• It took time to pry or chisel out the pin, often causing even more damage to the wood.
• It was difficult to measure wood deeper in a stack—where wood dries the slowest—without dismantling most of the stack.

The process was limited and time consuming. And the intense labor made it tempting to limit lumber moisture tests, or to skip them altogether.

But cutting corners with moisture testing led to the same problems then as it does now:

• Inconsistent dryness across a load, leading to unhappy customers
• Overdrying—which can waste kiln resources, bottleneck schedules, and cause degrade
• Underdrying—which makes wood prone to moisture-related problems like warping, mold, and lost contracts
• Excess labor costs and time from having to return wet loads to the kiln
• Profit loss from wood graded into lower grades
• And a damaged business reputation

But in the late 90s, Wagner developed the first lumber stack probe prototype. This led to the development of the L722 Lumber Stack Probe for use with the L622 Digital Recording Moisture Meter.

Lumber stack probes streamlined lumber moisture testing and revolutionized kiln-drying efficiency. It gave kiln operators the power to do quick, accurate, and consistent MC testing deep inside a stack of lumber without dismantling it or removing it from the kiln. And on top of all that, it removed the need to worry about dealing with pins or pin damage.

Bottom line: Lumber stack probes provided kiln-drying operations with a practical way to monitor the drying process and avoid lumber loss.

What Is a Lumber Stack Probe and How Does It Work?

A kiln-drying operation worker is able to get an accurate moisture reading from the middle of a stack of wood by using a lumber stack probe sensor.

Using a lumber stack probe is simple. Pair it with a compatible handheld pinless moisture meter and slide it between stickered boards to read moisture levels deep inside a stack.

As a reminder, you’ll need an industrial moisture meter for lumber mills—one that’s more durable and designed to work with a lumber stack probe.

We’ll refer to the Wagner 722 lumber stack probe paired with the new L5300 lumber moisture meter to explain how it works:

1. Plug the probe into a handheld moisture meter.
2. Select the correct species from the meters menu screen.
3. Slide the probe between stickered pieces of lumber to reach internal boards.
4. Let the end-mounted sensor springs do the work of pressing the sensor head flat on the surface of the lumber.
5. See instant readings on the backlit moisture meter without having to slide the probe out.

This setup makes it easy to get an accurate moisture histogram throughout a stack of lumber in mere minutes.

So how does all this work?

In pinless moisture meters, a sensor plate takes instant readings over the area beneath the meter. But when you attach a lumber stack probe, the meter defers readings to the sensor plate at the end of the probe.

It’s also easy to switch from measuring with the meter to measuring with the lumber stack probe by just plugging in the probe to the meter.

Lumber stack probe sensors not only make it easy to measure lumber without dismantling a stack, they also increase accuracy, even inside a cooling kiln.

Advantages of Lumber Stack Probe Sensors in Kiln-Drying Operations

A handheld pinless industrial moisture meter with a lumber stack probe attachment.

A lumber stack probe sensor (a probe paired with a lumber moisture meter) has multiple advantages that can improve productivity and profits.

Let’s break down the most important ones:

• Ability to read deep inside a stack
• Faster than past methods
• Designed for hot and cold checks
• Improved overall accuracy
• Has widespread adoption

Ability to Read Deep in a Stack of Lumber

The primary purpose of the lumber stack probe is to take accurate and efficient moisture meter readings from the inner boards of a stack. It’s an important step because the outer boards won’t give you an accurate moisture picture that represents an entire stack.

If you store lumber outside, the top and outer boards get the most exposure to the elements, including sun, rain, and airflow. And inside a kiln, outer boards often dry faster because of more exposure to heat and airflow.

If you make drying decisions based on the moisture levels of the outer boards alone, you could end up selling wood that’s not at the proper moisture targets. And it can cost you significant money.

Lumber stack probes make it possible to measure moisture without splitting the stack apart. And that saves you time, labor costs, and headaches.

Faster and Easier than Past Methods

Having a lumber stack probe is much faster and easier than using pin meters for three key reasons:

1. You don’t have to press pins into the boards for every moisture meter reading.
2. You measure a larger area per reading, since the sensor plate on a probe is much larger than the area between two pins.
3. You can take readings from inner boards without taking the stack apart.

Studies confirm that the pinless meter component itself is a big part of what makes this new method faster and easier:

• “The Wagner L612 meter was easy to handle, and in this study was capable of taking approximately four measurements within the same time that one measurement could be registered in a resistance [pin] meter.¹
• “During the course of the work, the greater ease and speed of use of Wagner Devices [pinless meters] could be noted, and their accuracy exceeded that of the Resistance Meters.”²

Designed for Hot and Cold Checks

Extreme temperatures can affect both pin and pinless moisture meters. But hot checks are possible with Wagner’s L722 Lumber Stack Probe.

Here’s a quick recap of important points for checking moisture in the drying process:

• During kiln drying if you’re creating a kiln-drying schedule for a specific product, every few hours or daily. This verifies the schedule is on track and avoids overdrying hardwood.
• At the kiln shutdown time, to verify that the lumber has reached target moisture content.
• Immediately after kiln shut-down, to confirm MC during the conditioning stage as drying stresses are relieved.
• After kiln drying, to verify boards reach target MC before storing or processing.
• Bonus: Before shipment, as a final quality control check in case boards absorbed moisture while in storage.

As a kiln operator, you know how important it is to check lumber MC to avoid waste, degrade, unhappy customers, and to monitor kiln consistency throughout the load or charge. But moisture checks take precious time, so having a meter for fast and accurate readings makes a huge difference.

With the L722, for example, you can take hot and cold checks:

• Hot checks: Inside the kiln before the wood has been pulled from the kiln or immediately after
• Cold checks: After the lumber has cooled down after drying, during storage, and before shipping

More Accurate Moisture Testing

Lumber stack probes paired with high-quality pinless moisture meters can improve accuracy in several ways.

Probes can measure deep within a stickered stack of lumber (usually reaching between 26 to 40 inches). This gives kiln operators a truer picture of overall moisture in a stack. And the ease of using a stack probe sensor versus a pin meter makes it more likely that operators will take enough MC readings for a complete moisture picture.

Several studies also confirm the accuracy of Wagner’s pinless meters over pin meters. Here’s what they showed:

• “The pin meters had a stronger tendency to over- or underestimate MC depending on the batch. In contrast to the pin meters, the L612 was nondestructive, and quick and easy to use.”³
• “On average the Wagner L612 Electronic Wave meter performed better than resistance [pin] meters under normal operating mill conditions.”⁴
• “Unlike resistance meters, the Wagner L612 meter required no air or wood temperature adjustment, nor did board thickness…have to be taken into consideration. This made the Wagner L612 meter practical to use in operational conditions, with less likelihood of operator induced bias.”⁵
• “Wagner Devices [pinless meters]…accuracy exceeded that of the Resistance Meters.”⁶

But beyond the studies, more lumber mills are seeing positive results for themselves.

Adopted by Many Mills

While lumber stack probes are revolutionary tools, they’re not new to the market. So, it’s a huge plus that many kiln-drying operations have already made them a regular part of their kiln-drying process.

And that shows how quality lumber stack probes are tried and true.

We’ve looked at five overall advantages, but let’s hear from kiln-drying operators in the real world.

Kiln-Drying Operation Success Stories

If you operate a kiln, you know the importance of moisture testing at every stage of the drying process.

Kiln-drying operators using Wagner L722 lumber stack probes to measure MC are seeing consistent benefits:

“The stack probe has been a great benefit to us. We’re getting truer readings than if you just get a piece that’s sticking out the end. That’s going to be drier than your stuff that’s down in the center. So, with the stack probe, that’s been a great advantage for us.”
–Kaster’s Kustom Cuttings

They also mention that with regular handheld moisture meters, they could only get to the top boards. But the probe allows them to easily measure inside the stack.⁸

Matt Farrell, a partial business owner of Burl and Grain Sawmill, says the Wagner lumber stack probe sensor boosted his ROI by:⁹

• Allowing for faster turnover rates
• Providing better accuracy
• Helping them get more done, faster
• Avoiding the need to desticker stacks for readings
• Speeding up kiln unloading times
• Saving on labor costs
• Lowering stress levels on the job
• Limiting unnecessary trips back to the kiln

Farrel summarizes his two biggest reasons:

“The first being that [it] saves a ton of time. And it is accurate and you can get through material without having to de-sticker it. The other part is that it actually reads deeper than most surface readers. So, we can go through material that is thicker…not necessarily have to pin or get into the core.”

Bottom line: “It gives us more confidence.”

And your sawmill or kiln-drying operation can have that confidence, too.

Stop Losing Lumber Loads. Use a Lumber Stack Probe.

Next time your product is too wet or too dry during or after the kiln-drying process, ask yourself a few critical questions:

• Is it worth losing time and accuracy by slowly poking holes in lumber outside the stack, while missing the full picture of moisture throughout the stack?
• Can you afford a kiln charge that’s too wet (much less load after load)?
• What’s it costing your business when your kiln stops drying consistently and you don’t have a tool to help you catch it early?
• How much time and labor are you losing by pulling a charge out of a kiln while it’s still not dry enough?
• Do you have a sufficient amount of readings to determine if your kiln is operating properly throughout the kiln/fans/coils/baffles/sticker airflow zones, etc.?

Without a solution to these questions, how are you recouping your costs?

If you want to keep your kilns paying for themselves, you need the right tools.

Arm yourself with the L722 Stack Probe, paired with the L5300 moisture meter. It’s a smart way to prevent painful profit loss and plan for peace of mind around your kiln.

Check out Wagner’s L722 Lumber Stack Probe to learn more.

And learn about the new L5300 Industrial Handheld Wood Moisture Meter while you’re at it.