Let’s start with a simple question; where do we find the wood?  Well, that’s complicated. 

I’m located on the east coast which limits the availability of wide slabs of furniture grade wood at a reasonable cost for a small shop.  My preferred species is walnut, more specifically black walnut, which makes it even harder to get the slabs I’m looking for.  Forget about Bastogne or English Walnut, it is virtually non-existent. You also need to consider the finished dimensions of your intended table.  You would think this would be obvious, but I have talked to other woodworkers that have gotten narrow or thin slabs and have a hard time getting the layout to look correct for their intended table. 

I would always recommend purchasing from a professional mill or supplier.  Yes, it’s usually more expensive.  Yes, I’m sure you can find slabs less expensive on Facebook Marketplace or Craig’s List.  The only advice I can offer: you get what you pay for.  I have found these locally advertised slabs to be less than ideal for the builds I’m working on (too thin or narrow, high moisture content, bugs in the wood, etc.) at best. 

You may ask, why do we care whether or not the slab is dry or what’s known as; equilibrium moisture content (EMC) in wood?  For starters when the slab is dried correctly everything is improved (strength increase, prevents color fading, cutting/machining cleaner, glues and finishes better).  It controls shrinkage over time as it naturally dries, which could cause warping or cupping.  It also kills any bug infestation.  That’s a terrible experience when you start pouring epoxy or your plaining to final depth and bugs start crawling out.  The EMC of furniture grade wood is typically 7%. 

So what’s going on in the wood while it dries that causes this improvement? 

Not being a microbiologist, the hard part for me to understand was what was going on with the cells of the wood and why it made a difference.  As simply as I can put it, there are two different types of water cells moving through the wood of a living tree; “free water” and “bound water”.  Free water is what is moving throughout the tree, while bound water is part of the wood fibers.  When wood is dried, the free water evaporates relatively quickly.  This gets the relative humidity down to roughly 28%, what’s known as “fiber saturation”.  Continuing with the drying process starts to remove bound water from the cells of the fibers, which causes the wood to strengthen and shrink as the molecules condense.

Well, why don’t we start a huge fire in the yard, elevate the slabs over it not to burn and dry it out?  Of course, it’s never that simple.  Dry the wood too slow and you can end up with stains on the wood from the water being extruded, dry too fast or too hot and you can end up with cracks or warped/cupped wood.  Ever go to a box store and have to rummage through a stack of lumber for a straight piece?  Ever wonder how there are that many planks twisted so badly? Well, now you know.  The process they use in the production of construction lumber dries wood so quickly it ends up causing imperfections in nearly every piece.  I’m fine with taking my time looking through a stack of 2x4s for the best ones.  But for live-edge slabs, the drying process needs to be done just so.  Long story short, it’s gotta be dry and dried correctly. 

So, how do we dry slabs properly?  There are several ways to accomplish this.  All of which require the use of a kiln at some point in the process.  But, we’re getting ahead of ourselves.  Let’s first look at air drying.

Air drying is pretty self-explanatory, you need a dry place with plenty of airflow to store the slabs during the process.  On one hand, it’s just that simple.  On the other hand, air drying takes a long time.  The accepted standard rate for “Green” or freshly milled slabs to dry to 7% EMC is 1 year per 1” of thickness.  In other words, if you have a 3” thick slab it would take 3 years to properly air dry.  Air drying will also not get you all the way home.  It the correct environment the slab will dry to around 20-30% EMC, but you will need a kiln for the last roughly 10-20% EMC

So what is a kiln? In a nutshell, a kiln is a void where the airflow, temperature, and humidity can be controlled.  There are several types of kilns, their names define the means by which they control temperature and humidity.  In commercial applications, you will most commonly find Dehumidification, Conventional, and Vacuum kilns.  If you’re really ambitious and have the space for it, you can build your own simple kiln.  There are several good YouTube videos out there describing DIY kilns. 

A Conventional kiln uses some form of heating element to raise the temperature in the kiln to remove the water.  This evaporated water is exhausted from the kiln in heated air.  This type of kiln produces good quality slabs, but in so doing uses a lot of energy.

A Dehumidification kiln uses fans to circulate hot air throughout the void, evaporating the water in the wood and drawing the water out of the air over a dehumidification coil.  Much like any dehumidifier you pick up at a box store, just scaled up.  This is the method that currently seems to be the most widespread, but not for long.

A Vacuum kiln is newer to the industry but has been around for some time (technology to produce dry slabs has finally caught up).  Water boils at different temperatures based on atmospheric pressure.  The higher you go, the less pressure there is, so water boils at lower temperatures.  By applying a small amount of heat and lowering the pressure within the void, you end up drying wood in a fraction of the time.  My High School Chemistry & Physics teachers would be so proud that I finally understand something from their classes. The vacuum kiln can easily cut down the drying time compared to both the conventional and dehumidification methods and will most likely be the future of the industry, however, they are cost prohibited to smaller suppliers at the current time. 

In the end, it doesn’t matter which method is used to transition from green wood to slab.  The most important thing when selecting your slab is that it’s dry.  There are several products on the market that can be used to determine what the EMC of a slab is.  I personally use a Wagner Orion 950 Smart Moisture Meter.  Yes, it’s expensive.  Yes, there are cheaper options on the market.  Perhaps in a future blog, I’ll go over my reasoning, but it comes down to the same premises we started with: you get what you pay for.  This is one of and in my personal opinion (not being endorsed by or compensated in any way) the best moisture meters on the market.  My meter lives in the glove box of my truck, so I always have it with me.  It’s a great tool and bailed me out of potentially bad purchases in the past. 

So where do I find my slabs?  When I was just starting out I did look at the online marketplace, and gave it the old college try, but simply put; it was a bust.  Pretty stuff for sure, and there were live-edge slabs, but not what I was looking for.  Searching within a 60-minute drive, I have found one supplier with vacuum kilns and one that air dries under (for lack of a better description) greenhouses.  Each has its drawbacks.  Specifically, the trees supplied in this area are not large enough to be milled for the tables my clients have been asking for.

Hope is not lost.  Nor have I been forced to settle.  The solution; Goby Walnut in Portland, Oregon.  I was a skeptic at first too when I first learn about them a few years back.  They were referred to me by another woodworker that was also frustrated with the lack of raw material in his region.  Since my first interaction with them, the staff at Goby Walnut has been superb every step of the way.  Their product is exactly as described and the quality is outstanding.  Their website is where the magic happens for me.  Each slab sis categorized by species, size, price, where in the drying process it is, you name it.  They offer several views of each slab which allows you to visualize your intended table.  The best part (provided it’s already dry) is I can place an order for a slab, and usually, within 10 days it’s being delivered into my shop.  Can’t beat it. 

You may think I’m being sponsored by or get preferred pricing.  Nope.  Just honest feedback based on my experiences with this vendor.  It comes down to this; I couldn’t make the piece I do, here in Charlotte, NC without my friends from Goby Walnut in Portland, OR.

So what is simple answer to the question: where do we find the wood?  You need to know what to look for and have some knowledge to ask the right questions.  I hope this article provides you with some of that education.  However to answer it simply, I get my slabs from my friends.

Thank you for reading.  Stay tuned for the next build update on the Black Walnut dining room table.