Seasoning is one of the most important factors in the furniture and door manufacturing industry, besides selecting the right timber, correctly sectioning, and properly sawing to your desired sizes and thicknesses. Without proper seasoning, door, frame, and furniture may be manufactured and used but the problem is, after a certain period of time the door and the furniture will naturally dry over the period of time. When they get dried they will shrink a certain percent and, that causes the whole problem. Since wood shrinks when they dry and shrinkage causes the wood to bend or crack, if the timber is matured then the shrinkage will be less compared to if the immature timber is used for manufacturing. This shrinkage issue is a big problem especially in frame and door manufacturing, if this takes place in furniture it is less noticeable but, when it comes to quality it’s a big issue. The quality of a door mainly depends on whether the door will bend or crack or not. So, whether we are manufacturing door, frame, or furniture, Kiln-Dried seasoning is a must. Proper seasoning doesn’t mean that, we will lay the timber in the sunlight with few sticks for 3 months and the moisture will come out and it’s done. For natural seasoning, we may stick the lumber properly and lay in a shade for 5/6 month, sometimes more, then the timber may be used for furniture, but not for the door.
When we are seasoning the timber naturally, it is drying slowly through porisrobon system, which is a natural and slow process but, doesn’t take care of the problem properly. The cellular membrane in the cells in the wood causes the problem, when we dry the lumber in a natural process, moisture from the lumber comes out of the cellular membrane of the tumbler gradually, and the cellular membrane shrinks while the moisture comes out but the cellular membrane stay active to suck the moisture in when it get the environment to do that. In the rainy days the lumber sucks the moisture in from surrounding air with a short time and releases it slowly through parisrobon gradually. Here a key problem with the factor of shrinkage and expansion of any wooden product is caused by the mechanism of the cellular membrane. When the tree is dead, who cares, kill the lumber properly, so that the cellular membrane mechanism doesn’t cause any more problems. We are going to destroy the cellular membrane permanently through mechanical seasoning, another word which is called Kiln-Dry, with this mechanism when the temperature in the chamber goes up to 100 degrees celsius, also the temperature of the lumber inside the chamber. The water inside the cellular membrane boils to steam and the volume steam inside the cellular membrane increases rapidly, the cellular membrane gets busted and get destroyed. Cellular membrane is the main reason for the expansion and the contraction of the lumber due to season change. Which causes the door to bend, crack, and honeycomb.
There are many different kind of kiln-dry in the market like, Solar Dry, vacuum-kiln, Natural gas heat Kiln-Dry, Firewood het Kiln-Dry. Any of this Kiln-Dry Chamber will serve the purpose properly, except the solar dry system, which is pretty time consuming and some of the cellular membrane may not be destroyed.
Why lumber blends
Kiln-Dry chamber is an insulated room with high R-value insulation, have an insulated door, which we can open or close for uploading and
downloading the timber, with a capacity of around 400 cft in each load. Has a heater of certain BTU capacity to make sure we can boil all the moisture out of the lumber in a certain seasoning time. We run the heater continuously at high temperature for 12 hours, and rest for 12 hours and continue this process for 4 days. After running the kiln-dry chamber for 48 hours, the moisture content comes down to 3-4%, then we let the lumber cool down in the chamber for several hours and take it out and let it sit for a couple of days to suck the moisture up to normal moisture content, like 14%, which is a standard moisture content for our country.
What happens during 96 hour
We organize the lumber inside the kiln-dry chamber with sticks size 1.5”x 2”, we create a gap
between the lumbers, every 18” to make sure the sticks are vertically straight and evenly distributed like shown in the picture;
Lumbers is placed in the chamber as shown above and circulate hot air through the stick gaps to the timber at 100 degree Celsius for 96 hours, Specially made heater beside the chamber produces the heat and circulate through the lumber in the kiln- dry chamber, with a powerful blower to pump the hot air from the heater to the chamber and lumber. Due to this high temperature, most of the moisture will turn into steam and the chamber get supersaturated with steam and we take the steam out through a special condensation system, so there will be no damage to the lumber, while the temperature is up to 100 degree Celsius the moisture inside the cellular membrane turns in to steam, where the volume of steam is 1700 times than the water inside the membrane, so the membrane gets busted and destroyed instantly. The moisture-absorbing mechanism gets destroyed, no longer in the rainy season the door can get expanded out of limit.
Diagram of the seasoning chamber.
Cellular membranes can only be destroyed by the mechanical kiln-dry chamber and get rid of the expansion and contraction mechanism. Not knowing, some people make comments like, seasoning timber with mechanical system temper of the timer get weaker, which is not true at all, timber get longer life and get stronger. There are many other ways manufacturers dry their timbers, some of them are not profitable for commercial purpose, some of them are quite expensive to purchase the chamber, some of them are expensive and some of them are very time consuming, which is not suitable for commercial use at all. It is essential for the large wood industry to have the timber air dried first, whether they are doing just for seasoning or the manufacturing, whether the door, frame or furniture
Image of a cell with the cellular membrane is shown
After we get the timber out of the chamber, we make sure the moisture content is within the right position, we test the moisture content with a digital moisture meter to make sure of that if we find the moisture content over 14%, we let the seasoning chamber run for little longer and check before we take the lumber out of the kiln- dry chamber, the moisture content usually contains to 3-5 %, now know for sure the cellular membrane are completely destroyed as we desired, and after couples of days, moisture gets up to 13-15 %, after from air. Now we know the lumber is ready for machining and make a door, frame, or Furniture.