It All Starts at the Mill
Drying live edge wood slabs properly is one of the most important, and often overlooked, steps in creating a one-of-a-kind piece of furniture. When slabs are pulled from our mill, they are stacked with evenly spaced sticks separating each layer. These sticks create a space between each layer for air to flow over the surface of the slab, allowing moisture near the surface to evaporate. This is the start of the air-drying process. The air-drying process can take anywhere from 1-3 years depending on species and thickness of the cut slab. The general rule of thumb for most hardwoods is to allow them to air dry 1 year for each inch of thickness. Most of our slabs are cut between 2” and 3” thick; so, a 2” slab will need to air dry for 2 years. This is to allow all the “free water” in the woods cellular structure to be evaporated.
Once the free water has been removed the wood will usually have a Moisture Content (MC%) of 18%-22%. The slabs are then be put into our vacuum kiln to remove the bound water, which is the moisture built up in the walls of the cellular structure. Our vacuum kiln uses heated aluminum plates and a vacuum chamber to remove the remaining moisture from the woods core. This process can take anywhere from 4 to 7 days. Once complete we check each slab to make sure it has reached a MC% of 6%-8%.
Why Is Kiln Drying Important?
Kiln drying live edge slabs and lumber has a lot of advantages. The first being to make sure that any boring insects and their larvae are destroyed before entering your home. Powder post beetles are a common threat to live edge slabs and lumber. In the final step of our kiln drying process, we will heat the wood core to over 170 degrees Fahrenheit for over 24 hours to make sure these pests don’t make their way home with you.
The second advantage has to do with stability. As green (freshly cut) lumber loses its moisture, it shrinks. Most hardwoods will see 6%-10% tangential shrinkage, 3%-5% radial shrinkage and usually less than 1% longitudinal shrinkage. That means a piece of wood can shrink anywhere between 9% and 15% overall.
If the slab you choose has not been properly kiln dried, it could mean disaster for your project because as the wood shrinks it will twist, warp, and/or cup exposing screw heads and popping glue joints.
After the drying process
Wood is always interacting with the relative humidity (RH) in the environment; gaining and losing moisture until it comes into equilibrium with the environment. This is called EMC or (Equilibrium Moisture Content). Temperature and Relative Humidity work together to give us our EMC. These conditions will vary across the United States at different times of the year. Typically, you’ll see RH between 40% and 50% and temperatures between 65 and 75 when climate controls are used in the house.
Wood inside a home where the RH% is held at a consistent 40%, and temperature at 70 degrees Fahrenheit, will have an EMC% of around 7.7%. Here in the northeast, many older homes don’t have climate control, so RH% can change drastically throughout the year. Many shops and garages aren’t climate controlled either. This means you’ll need to be careful how your new live edge slab is stored. If your slab needs to be stored for a long time before you work on it, it’s best to leave it wrapped in plastic to act as a moisture barrier. Once you are ready to work on it, it should be laid out flat on sawhorses or a bench and left to acclimate to the environment for several days. It’s important to make sure each face of the slab can gain any moisture back equally as to reduce any cupping.
To check the EMC in your home, you’ll need to know the average temperature and RH and reference that with the chart at: http://www.csgnetwork.com/emctablecalc.html.
Why Berkshire Products Live Edge Wood Slabs?
We have over 35 years of experience with Lumber and Live Edge Wood Slabs drying, so we know how important it is to our customers that the piece they choose for their home has been kiln dried right. We monitor conditions in each of our warehouses and we check each slab each slab we sell for issues so the customer can be confident in what they are receiving.
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