Kiln drying is an important practice that is required for wood production which serves to efficiently lower the moisture levels of green lumber to a workable-range moisture level that will not end up causing problems often associated with the presence of excess moisture in wood. Some of these include warping and cracking, binding, or kicking during machining, crowning, and other adhesive failures in the finished products. These moisture-related damages can cost millions of dollars in damages every year. The first step that would help bring wood products to moisture content levels that would be subjected to minimal moisture-related damage is kiln drying.
Kiln dry wood at home, step-by-step method:
- Step 1: Mill the Wood
- Step 2: Determine the Moisture Content
- Step 3: Air Drying
- Step 4: Build the Kiln
- Step 5: Using the Wood
Now kiln drying your own wood at home can be very cost-effective, and you’ll be able to dry the wood to a moisture level that you prefer. It is also a sustainable way to harvest the materials around you, drying it fast enough for you to build woodwork with. If you make a piece of furniture with wood that is still wet, the finished product will continue to dry and eventually crack, and it may end up ruining the piece. Do you want to know how to kiln dry your own wood at home? This article will walk you through the step by step process of drying your lumber at home. Sit tight!
Principles of Kiln Drying
There are two major factors that determine the drying rate of wood you kiln dry. These are:
- Movement of water from inside the wood to the surface of the board
- Evaporation of the water from the surface of the board
Step-By-Step Method on How to Kiln Dry Wood At Home
There are different resources available that offer plans for building a home-based kiln, and also provide greater details about the kiln operation as well as kiln-dried wood. In kiln drying, the lumber is usually stacked in a closed chamber where warm air is mechanically circulated. Here, the air circulation, temperature, and humidity is relatively controlled so that the moisture content is brought to a level where drying defects can be avoided. The moisture emitted during drying is drawn away, and this causes the process to speed up significantly. Kiln drying reduces the drying rate to about one week per 25mm which results in moisture content of just 8% – 10%. However, this process should be carefully controlled to avoid placing undue stress on the substructure of the wood as it dries rapidly. If this occurs, the core of the timber can become very weak and it will not even be externally visible. That being said, here are the step-by-step methods of kiln drying wood at home:
● Step 1: Mill the Wood
The first step here is to mill your wood. Cut down the tree logs using professional chainsaws just like those used in sawmills, together with other necessary equipment in order to have wood of required size and shape. Also, proper sizing of the logs is a very important step in getting the woods to dry perfectly. The perfect time to cut the wood would be before winter to avoid humidity, and I would recommend that you do so in early summer or spring months. Depending on the log, you can even decide to mill it yourself using a chainsaw. However, if you’ll be doing this, ensure you follow the safety instructions highlighted in the user’s manual.
● Step 2: Determine the Moisture Content
It is important to know that there is no accurate visual test for determining the moisture content of wood. However, to make sure your wood is at the perfect moisture level for woodworking, you’ll need a small tool called a moisture meter, which would help you determine the accurate moisture content of the wood. This tool usually features two metal probes that must be placed against the wood, and after a short time, it will display the actual moisture content of the wood. Typically, for most woodworking projects, the maximum acceptable moisture content is 7%. If the moisture content of the wood is higher than that, then it must be dried again to attain this level. To make things easier, you can seal up the end grains of the wood so as to close the open pores. You can also decide to wax or paint the pores in order to close them. If this isn’t done to the end grain of your timbers, they will eventually crack and split up as moisture leaves the wood.
Once your lumber has reached the correct moisture content that is acceptable, the next thing is to equalize and condition it. Equalizing and conditioning (also known as stress relief) are two quality-control measures that are carried out to complete the drying process of high-quality hardwoods. Once they pass these measures, the woods are good to go.
● Step 3: Air Drying
Air drying simply means exposing your woods to natural air and sunlight to achieve drying. You can start by doing this for a few months in order to naturally get rid of the first bit of water (a loss of about eight to ten percent). This process is usually important and produces better results. There are some key factors to pay attention to when air drying. Ensure that you stack up the woods with lots of stickers or spacers under the natural air and sunlight, to allow for a good flow of air. The woods should never be used as a sitting place while they’re drying. The ground on which the woods are placed should not be humid to avoid negative effects on the lumber. The timbers should also be placed in a location with prevailing winds, as this would go a long way. You can also place some already dried wood such as some old 2 x 4’s, and lay them out evenly with about 16 inches of space in between each of the stickers. These woods act as an elevated base, hence air can easily get to the wood from the ground, and the moisture from the ground does not make the wood even wetter.
● Step 4: Build the Kiln
After a few months of air-drying the woods, you can now bring them indoors to complete the drying. In order to do this, you will need to build the kiln. You will also need to construct the insulated kiln box by yourself. Here, two plans are involved; the first one involves using an insulated wooden frame, while the other involves using structural floor insulating panels. Building a kiln yourself not only reduces investment cost but also allows you to save enough when compared to other drying methods. To build the kiln, lay the clear plastic roll on the ground and build a wooden frame with 2×4 studs on top of it for the lumber to rest on. Remember to make space for a standard household dehumidifier at one end, and a small fan at the other for artificial airflow. This will help to dry the woods faster and better before the expected time.
The kiln is usually built around stacked and bound lumber, and over a light wooden frame that carries the clear plastic. All the seams must be sealed using a vapor barrier tape in order to effectively hold the moisture in. You may also decide to cut a few small access holes to control the dehumidifier and for testing the moisture content of the woods in various places. Always remember to tape up these holes after you use them to avoid exposure. The woods can remain in the kiln for as long as 4 months and would have reached an average moisture level of 8 percent.
Building your own kiln at home is very effective, and you can even make the arrangements on your own by using the dried woods in your woodworks. Finally, the kiln performance can be effectively monitored by taking kiln samples which should be selected from the kiln during stacking. The number of samples selected usually depends on the condition of the wood being dried as well as the drying characteristics. The type of kiln used is also taken into consideration.
● Step 5: Using the Wood
After attaining the suitable moisture content, take the wood into your workshop and leave it to acclimate for a few weeks before you start processing it.
● Step 6: Making Furniture
By following these procedures, your wood should be ready for making the furniture that you desire. Using this unique wood often presents you with the opportunity to actually showcase that unique woodwork that you can be proud of harvesting in a sustainable manner.
Always remember that whatever you choose to do, ensure that the wood has a moisture content of less than 8% in it. In addition, it is important to always have a moisture meter to help determine the exact or correct moisture content. From when you mill the wood to the final finish, the woods moisture content must be accurately measured, not just in the kiln but also at each step on the way to its final use.