The RFV kiln drying process is fairly complex. In a nutshell, we are drying the timbers in an oversized vacuum chamber microwave. Here's an overview of the dynamic drying process from start to finish.

First, a specialized computer program is utilized to indicate the most efficient use of the kiln chamber as it relates to the species and size of timbers to be dried. The RFV kiln chamber can dry timbers of virtually any thickness and width, and accommodate lengths up to 42 feet!

The timbers are loaded on to the RFV Kiln carts via a vacuum crane to avoid any damage than can often occur with standard cranes or forklifts.

Large Alaska Sitka Spruce timbers waiting to be loaded into the RFV Kiln.

The carts are then rolled into the kiln chamber where a near perfect vacuum is drawn. Radio Frequency (RF) electromagnetic waves are generated by a power amplifier system at a set frequency controlled within the confines of the vacuum kiln chamber. These RF waves are sent uniformly throughout the wood. Prior to being subjected to radio waves, the water molecules within the timbers are not aligned. RF waves generate electromagnetic forces causing the water molecules to align. This realignment of the water molecules allows the vacuum to draw the moisture content evenly out of the timbers.

The RF waves essentially move the moisture out of the wood from the "inside out". The RF waves agitate the water molecules throughout the timbers heating them to a boiling point. The subsequent steam generated moves parallel along the grain structure of the wood and out through the ends of the timber by the vacuum pumps. Since water moves up to 10,000 times more easily longitudinally than in other directions, drying schedules of four to five days are the norm.

By controlling the rate and frequency of the waves for each load being dried, the timbers are dried uniformly throughout, from the center core to the surface of each timber. By drying the wood under a perfect vacuum, we can get the moisture to vaporize at very low temperatures. Under vacuum, the water present in the wood can vaporize at 90ºF (30ºC) compared to 212ºF (100ºC) with conventional kiln drying methods. This is a huge advantage over conventional drying in that lower temperatures allow us to move large volumes of water out of the wood with minimal splitting, cracking, twisting or checking.

The final element of control is our ability to build timber loads that are hydraulically strapped and therefore stabilized under uniform pressure. A compression plate that distributes the RF waves also

This 42’ long, 36" wide, and 18" thick Alaska Sitka Spruce timber is removed from the RFV Kiln and ready to ship.

applies up to 250,000 lbs of pressure to the timber load (roughly 10,000 pounds of hydraulic force for every 4 cubic feet). This awesome force allows the timbers to be held in a straight and flat position which minimizes the movement of the wood during the drying process. This final step in the RFV kiln drying process helps Arc Wood & Timbers to produce a straight and stable timber that is dried uniformly throughout with minimal surface checking.

All aspects of the RFV Kiln drying process are monitored and recorded by computerized sensors within the kiln chamber. The data is evaluated and documented by technicians allowing Arc Wood & Timbers to build a comprehensive "drying" database by species of wood. This growing knowledge base allows us to continually improve our drying capabilities for all species and dimensions of lumber.

This level of detail is unparalleled within the timber industry. At Arc Wood & Timbers, we are not claiming that all our timbers dried by the RFV Kiln will not have checks or move, but we are claiming that our timbers dried using this method are by far the most stable product available in the market today.