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| Collector's Specialty Woods is tackling wet lumber head on. Contractors, architects, and woodworkers everywhere know how important it is to work with dry lumber, and in a dry climate like Colorado, it is even more essential. We are focusing on the problems: getting wood dry in the middle of the board, drying thick stock, drying without causing tension in the wood, maintaining natural colors, and getting material dry in weeks, not months or years. We have just finished and are operating our new dehumidification kiln, and we expect delivery of our new state of the art vacuum kiln this month. Call us - we can dry your wood! |
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Now Drying: Timber Frame Packages
Logs for Log Homes - Thick Tops - 8/8, 6/4, 4/4 Lumber |
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To dry your lumber (or for more infomation): Call - 800.746.2413 or Email Us
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Vacuum Kiln: 2500 board feet |
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| CSWoods will soon be running a brand new vacuum kiln. This state-of-the-art AirVac kiln, made by Vacutherm, will allow us to dry material to order in a very short time frame - from green to dry in a week and a half for most species, and much less on material already in stock. This programmable machine will have a low defect rate, and be able to actually flatten lumber. Its computer controlled system is able to recondition the skin on material so that it releases moisture at a controlled rate, keeping the tension in the lumber low. This 2500 board foot kiln (5' wide by 18' long) is due to arrive this month. If you are interested in more information about these kilns, or have some lumber in need of drying, we are happy to answer questions and possibly schedule dry times. Please call for pricing.
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DH Kiln (dehumidification): 7000 board feet |
| The solar kiln at Collector's Specialty Woods was converted over the last 4 months into a DH Kiln. This included the installation of fans, a dehumidification box, drainage system, and power storage area. Dehumidification kilns use the continuous cycling of heat and water condensation to dry lumber. Instead or heating the lumber till it releases moisture into the air, and then venting the saturated heated air, water is condensed on dehumidifier coils and then removed as liquid. When the hot air passes over the cold refrigeration coils, the evaporated moisture from the wood condenses to liquid and drains away. This recycling of heated air is more efficient, and although these kilns use electricity to both heat and cycle the air, a set of heater boxes filled with special bricks are heated during off peak hours and used to store and disperse the heat when needed. |
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A DH kiln is loaded from wall to wall so that the air current is moved throught the stacks of lumber. |
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Dehumidification Kiln: sticker stacked Douglas Fir in the kiln |
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Kiln Schedules and the minimization of drying stress |
| Kiln schedules are developed for each species and the thickness being dried. This schedule is essentially a plan outlining the temperature and humidity cycles needed to dry the specific material with the least stress on the wood. Drying stress can result in a wide variety of defects from the tension and compression of wood as the water moves from the inside out. Wood will dry faster on the exterior of the board, thus the exterior shrinks at a faster rate then the interior creating tensile stress on the outside and compression stress on the inside. If this stress exceeds the level that the specific species of lumber can handle, surface and end checking and even cell collapse can occur. It is also possible to cause what is referred to as case hardening. Case hardened wood has surface compression stress because the outer layer dried and set but the center of the board continued to shrink. This leads to over stretched fibers on the outer surface and a strong tendency toward cupping. It is possible to relieve case hardening using a kiln and controlling the atmosphere, but with a good kiln schedule, case hardening can be avoided completely. |
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The importance of dry lumber - history and progress |
The wood world is full of anecdotal claims from wood suppliers and woodworkers about the process of drying lumber, and which process yields a better, more stable product. Although some of the claims can be chalked up as folklore, the discussion is one of the most important in the lumber industry. This issue of moisture content weighs heavily on the minds of everyone involved with wood.
Before kilns, all wood was air dried and, because it is the 'old' way, this process is usually highly respected. Although it sounds simple, air drying lumber properly is a long arduous process involving sticker stacking, waxing, moving, constant checking and restacking. The invention of kilns and the ability to dry lumber more quickly was of great benefit to the wood world, but there is a question about what the process of kiln treating does to the lumber and how stable the resulting product is. The drier the wood, the stronger but also the more brittle it is. Although some believe that it does not matter how the lumber got that way, air or kiln, there is research to suggest that air drying can result in a stronger and more elastic product. The Encyclopedia of Wood cites a 40% greater modulus of rupture (strength/hardness) without heat and or moisture from kiln treating and up to 15% greater modulus of elasticity (can expand and contract with changing equilibrium moisture content conditions without splitting or cracking at glue joints). This doesn’t mean that kiln drying should be avoided, but it is a reminder that kiln operators must be careful, constantly managing the load and monitoring the temperature and humidity. In order to yield the best product, the kiln operator needs to be experienced with the species of lumber and ratio of heat and time needed to reach the desired moisture content, without forcing it to conform to their latest delivery schedule.
At CSWoods, because of our dry climate, we can air dry lumber to around 7%. This process takes years of attentiveness, tying up capital and inventory. On site, we use a solar kiln and a dehumidification kiln, and we will soon be installing our own vacuum kiln to speed up the process. This will allow us to carefully dry wood for clients in a week, ensuring that they are getting the most stable product possible. We are constantly working to educate ourselves, our suppliers and our clients about drying lumber, and the right moisture content for their region. |
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Teak beams and wide plank walnut tops waiting to be dried in the new DH kiln. |
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