Kiln drying is a standard practice that is employed in wood production mills as it efficiently helps to reduce green lumber moisture levels to workable-range moisture content levels, hence it does not lead to most problems that are usually caused by the presence of excess moisture content in wood. Kiln drying process of wood involves the drying of lumber or wood in a controlled chamber where the air circulation, temperature, and relative humidity can be relatively controlled so that the moisture content of the wood can be lowered to a specific point where there are no drying defects. Normally when lumber is first harvested, it is referred to as “green” – which means that it has not been dried. Because green lumber tends to be very moist, it will always shrink for every percent of moisture content below its standard fiber saturation point. This shrinking will still occur regardless of the drying method used.
Use Kiln to Dry Wood, The Fastest and Cheapest Way:
The best balance between speed and cost to kiln dry wood is to use a solar kiln. They are relatively easy to use and well suited to dry smaller quantities of lumber and wood. Several homemade solar kilns can be built for around $600-$700, excluding a moisture meter. The major operating expense is electricity that is needed to run fans for hot air circulation.
Before the conventional kiln drying method was introduced, woodworkers would simply go to a local sawmill or a lumber retail store to buy their lumber, especially the kiln-dried material, for their jobs. In most cases, these wood materials do not end up being exactly what is needed and may even cost more than the wholesale price. Applying a custom lumber-drying method to dry green lumber which is sawn for use by the woodworkers can be relatively expensive. Kiln-drying of lumber is an expensive process which is why kiln-dried lumber is sold at a significantly higher price than green lumber.
Typically, the most kiln-drying process of lumber is done by conventional and dehumidification kilns, and these operations are usually energy-intensive and require high cost. To save costs, some woodworkers simply air-dry their lumber material. Some individual woodworkers even prefer to use other cost-effective methods to help lower the cost of purchasing kiln-dried lumber cuts. So you want to know the fastest and cheapest way of kilning lumber? Are you interested in saving costs? You’re in the right place. In the rest of this article, you will discover the different types of kiln drying methods as well as the cheapest and fastest way to kiln-dry your woods.
Contents
Different Types of Kiln Drying
Solar Kiln
Solar kilns are kiln drying methods that generally depend on some kind of solar collector that provides the heat energy that is responsible for evaporating the moisture present in the lumber. This method is quite effective and will save costs. However, drying in a solar kiln depends greatly on the weather condition which makes this method generally unpredictable. In hot weather conditions, they can degrade lumber as a result of excessive drying. In cold climates, on the other hand, they can be extremely slow and unreliable.
Dehumidification Kiln
Dehumidification kilns have become one of the most commonly used kilns in wood production industries. One of the advantages of using these kilns is the continuous recycling of heat within the kiln, instead of discharging the heat from the kiln as in the case of conventional kilns. Most of the moisture is usually condensed on the coils of the dehumidifier and is removed in form of liquid instead of being ventilated to the outside of the kiln. While dehumidification kilns make use of electricity as their source of energy, which is more expensive than gas, they are still very economical than conventional kilns because of their heat recycling process and are also more environmentally friendly. While they are relatively cost-effective, dehumidification kilns are still more expensive than solar kilns, however, they can provide top-quality kiln-dried lumber all year round regardless of the weather condition.
Conventional Kilns
Conventional kilns make use of steam which flows into the kiln through pipes and radiates heat into the kiln. Here, the moisture in the wood is converted to vapor and is discharged from the kiln as hot air. Although quite effective, conventional kilns require large amounts of energy making them neither economical nor efficient compared to other kilns like the solar and dehumidification kilns.
Vacuum Kilns
This type of kiln is very expensive so much that the less commonly used vacuum kiln is about 3 times more expensive than conventional or dehumidification kilns. This huge cost is due to the limited drying capacity in the chamber. However, the biggest advantage of this method is the extremely high-drying speed.
The Fastest and Cheapest Way of Using Kiln to Dry Wood
As discussed earlier, kiln-dried lumber tends to be very expensive. This is why woodworkers may prefer to dry their wood as it also helps assure them that they are getting the moisture content they want. One cost-effective option for woodworkers is to air-dry wood. Air drying, however, can take up to several months and will still not achieve a moisture content that is low enough without an additional step of kiln drying. Therefore, a simpler, faster, and cheaper way to dry wood is by using the solar kilns method. You may even decide to build a backyard solar kiln, which is relatively inexpensive and is easy to operate.
Due to its low cost and simple mode of operation, solar drying lumber can be considered one of the attractive methods of drying small quantities of lumber and wood. Several homemade solar kilns can be built for just about $600-$700. The major operating expense here would be electricity, which will be used to run fans for hot air circulation. Also, these solar kilns do not require a large space making them very convenient.
Greenhouse Kilns
A solar collector is a device that indirectly extracts solar energy from the sun, and converts it into a usable form. A common type is a greenhouse kiln which is a simple construction with a lumber frame made out of plywood or oriented strand board (OSB) sheeting. When using this solar kiln, the floor and walls must be well-insulated to achieve an efficient drying process. The common solar collectors in these kilns make use of glazed glass, fiberglass or plastic sheets, which are directed towards the south.
Several factors control the amount of heat that can be obtained from sunlight. However, the most important one is the slope of the roof. The ideal angle of the roof depends on the geographic location, but usually, it is set at an angle of 40-45 degrees to the south. Note that there is usually some variation due to the wood species.
Another important factor that controls the quality of the dried wood or lumber is proper air circulation. There are usually one or two fans located on the top of the kiln, which is used to remove moist air from the surface of the lumber. The ideal circulation rate of air through the lumber should be around 150 feet per minute and nothing more. If this volume is multiplied by the total space openings, the average cubic volume of air required in the kiln can be calculated.
External Collector Solar Kilns
Unlike the greenhouse kiln method, the overall process of an external-type collector solar kiln is much more complicated and twisted. Ideally, the surface area of the external collector is approximately 1 ft2 and this goes for each 8 to 10 board feet of lumber with a thickness of 1 inch.
The way this solar kiln operates is much more complicated and requires technicality. However, during the drying process, temperature and relative humidity can be generally monitored using a sling psychrometer that has both wet and dry bulb thermometers. Also, depending on the size of your kiln, one or more sample boards should be removed to find out the moisture content of the load. These samples are usually weighed at an accuracy of one gram before they are then placed into the oven at a temperature of 214-218 degrees Fahrenheit (or about 105 degrees Celsius) until they can reach a constant weight.
This particular process often takes about 18 to 35 hours depending on the species of the wood you’re working with, then the moisture content can be calculated after. As a general rule of thumb, lumber must not be dried at a drying rate that is more than the required moisture content loss per day. If this happens, some drying defects such as warping, surface checks, and even splitting may occur, and this will reduce the final quality of your lumber.
Final remarks
For professional woodworkers (or other people that consider this a hobby), who are willing to save cost and generally avoid the high cost that comes with commercially kiln-dried lumber, a homemade solar kiln may be just the best option. These kilns are quite inexpensive to build and are easy to operate. Additionally, besides the small cost of electricity required to run the fans, they cost only a little amount to operate daily. However, woodworkers need to use a moisture meter to ensure that the solar kiln does not dry wood too fast. This will help in monitoring the moisture levels to prevent cost defects in a finished wood product such as cracking or warping.