We offer hardwood lumber kiln drying with both our premium vacuum kilns. Our custom design controls are set to dry wood up to 4" thick in amazingly short time! Traditional kilns pull moisture from only the surface of the wood. Because our vacuum kiln pulls moisture from throughout the entire board, boards are dried much more quickly and at lower temperatures. The boiling point of water is reduced under vacuum, and heat is applied directly to the lumber. This effectively forces the moisture out of the core of the board by turning it to vapor and enabling it to flow through the fibers of the wood more easily than traditional drying methods.
The total drying times for 1 inch thick hardwood lumber boards are usually less than a week. Also, boards as thick as 3 inches and thicker can be dried in the vacuum kiln. The lumber is dried without the use of "stickers," the spacers that are used with most drying methods. Instead, heating blankets are placed around each row of lumber as it is stacked in the kiln. This prevents sticker stain that often happens to light colored lumber such as maple or basswood.
We meter every board/slab on both sides in many spots. It is common that thick material can require 2 passes through the kiln to dry. The first pass through the kiln usually takes approximately 10-> 14 days. The slab is allowed to acclimatize for at least 1 week (1 month is preferable) between passes. This allows the moisture content remaining in the slab to equalize which improves the overall drying for the second pass. The second pass is shorter; typically 5 to 7 days.
We have dried 1000's of thick slabs in the past 10 years. Drying thick slabs is more difficult than drying standard 1" material and is not an exact science. Some species dry more easily than others. Some species are more reactive than others. We recommend allowing the slabs to rest for several months before using them in your project; it is best not to rush this process!
Board lengths are critical for efficient loading. The kiln chamber is 25 feet long and 32" wide, so lumber stacking is done by laying two 12'6" boards end to end, or two 10' boards with a 5' board, etc. 8'4" and 12'6" are ideal lengths for the kiln, but any size will be accommodated using "fillers" placed in the row. Please be aware that the customer is paying for the space of that filler.
A minimum load of 250 bdft is required to run the kiln, with a maximum capacity of 2000bdft per load. Similar species should be dried together. The charge for all runs of less than 250 bdft will still be set at 250bdft. Actual drying time once the kiln is started varies but is usually around one week. Air drying the lumber before kiln drying is a good idea.
In order to maximize your space within the kiln (and to reduce your costs), we may have to trim over-length lumber to the above lengths. Typically this trimming is less than 6", we try to trim the lower grade boards where possible, and we trim the worse end of the board.
Our hardwood lumber and services pricebook lists all of our current pricing. Are you new to having logs sawn or lumber dried/milled? Have questions on how the process works? We can help. Our What To Expect page is a good place to start. We also have a Frequently Asked Questions page to help you understand the process better.
Whether you are air drying or kiln drying your lumber, the moisture content should be stabilized to be desired location before use. In the Midwest that means wood intended for indoor use should be dried to 6->8% and for outdoor use 10->14% moisture content. To get a better understanding of how wood dries, visit this article: Understanding Moisture Content and Wood Movement. The article mentions the following helpful rule of thumb:
Most species of flat grain material will change size 1% for every 4% change in MC. Applying this formula to a situation where the seasonal EMC ranges from 6% to 10%, a 12-in. wide board will change dimension 1/8 in.