According to the U. Forest Service's Forest Products Laboratory in Madison, Wisconsin, it takes 1"-thick green boards from days to air dry to percent moisture content in sunny, temperate, not-too-humid weather.
If you live where it's colder and damper, count on more time. Inside, the drying process can prove slower, taking three or four months before the wood reaches its EMC and can be worked. But achieving workable stock means starting with a proper stack.
Pick a storage spot for your boards that's in the open, but avoid low, damp, or boggy areas. And, keep the stack from under trees that can litter it with twigs and leaves. On the other hand, don't pick the sunniest spot in your yard—your boards might dry too rapidly.
Keep wind direction in mind, too. Says the experienced Robert McGuffy: "The [prevailing] wind should blow through the side of the stack, not through an end. It'll dry much quicker going through the side, and you won't get end-checks. At Anderson-Tully, Robert takes extra precaution so the green boards won't degrade in the drying process. Home woodworkers can do practically the same thing, notes Robert.
You may find some variance in the thickness of your green stock. Stickers create gaps between the layers of wood. These gaps allow air to flow freely through the stack.
Make your stickers from dried wood. They should be straight-grained and strong, so they can be used over and over again. Use 2- to 3-in. The extra width helps slow the rapid loss of moisture at the ends of the boards and makes the stack more stable. Stickers should be slightly longer than the overall width of the stack. It is essential that each sticker be place directly in line with the one below.
This creates a vertical column that transfers all the weight of the stack to the foundation. In box-piling, full-length boards are used on the outside edges, and shorter boards are placed in the interior of the stack. Fill the voids at the ends of the pile with offcuts from trimming.
Can I use a kiln to dry out the retreads and will they straighten out? Is there any advice that anyone can offer to help me out of this expensive error. I was … Read more ». Ouch, that sounds like a very unfortunate turn of events! I do not believe that simply drying them or otherwise adjusting the moisture content will be the standalone solution. You might try a combination of weight and lowering moisture content. Maybe someone else can chime in with better ideas.
While traveling the Great Lakes, I visited a colonial style boat building display. They were using a homemade steam box to heat the wood to allow it to be bent around the bow of the boat. Would it be possible to steam the boards, the lay them on a flat surface with good stripping and weight on the top to force them back straight?
Might salvage by planing thinner or squaring up 2-inch strips and edge-gluing. Not a bad look and done historically for more stable surface. A good experiment is to take a thin, partially-seasoned, plain-sawn Pine board, throw it on a moist lawn on sunny day and see how fast it cups.
Turn it over … Read more ». Cut the boards into 2 in strips alternate the cup and glue back together. Lots of work but the only way to eliminate cup. Honestly I would advise getting them as wet as possible then weighing them down heavy and letting them dry, steaming would be most effective followed by weight. At what mc can I do the heat treatment? I just picked up 4 , 6 x 6 posts 10 foot long to replace front porch pillars. Green treated. What is the best way to dry these before use? If so, leave that bad boy in the sun for an hour or so, the slime will dry off quick, just be sure to install them not long after.
Drying bowls is a different process than flat slabs of wood. Keep rough turned bowl inside a paper bag or double bag for sensitive species and then weigh it intermittently until the piece stops loosing water weight. After that, it should be ready for final turning. Several good schools o f thought here — I turn wet Cherry to the finished dim and shape then use planer chips from a hardwood Walnut pack the piece tightly in these shavings in a paper bag and inspect a month later.
Uaually I win! But this year there have been some bigger limbs coming … Read more ». I believe that kiln drying walnut actually causes some colors to be lost, your best bet, with regards to color, is to air dry the material. Walnut color is highly variable depending on growing conditions. Sapwood is a pale gray color and can take up at least a few inches of the outer edge of the stem.
Has any one else dried wood in a microwave? I play with a lathe and have have had good luck cooking small raw pieces. Red cedar scents the shop kitchen too. I will be sawing beams from sourthern pine for timber frame. Up to 30ft. A year for each inch in thickness is the standard drying time for all timber. Great job there. Easier to slice through than Ironbark!.
I just bought rough cut lumber to build a wall in my basement is there anything I need to do to prepare it. I just got 2 8 ft long planks of wood with crusty bark on the edges.
Should I seal the ends with something while it dries? I plan slow on drying it in my house and then making shelves with the wood. Any other advice about drying or working with these planks is appreciated.
I recently acquired two dozen or so logs of silver maple. I sealed the ends with end grain dealer within about 24 hours of them being cut down.
You can help support the site by buying one of these resources, designed and published by The Wood Database. The specific links on this site are affiliate links as an Amazon Associate I earn from qualifying purchases and help support the site at no extra cost to you. See my page on donating wood samples for more info. Drying Wood at Home. Drying times can vary significantly depending upon wood species, initial moisture level, lumber thickness, density, ambient conditions, and processing techniques.
In situations where green wood is to be processed into usable boards, especially in the case of thicker lumber , a kiln is frequently used to control the drying process. While there are various types of kilns used to dry lumber, the basic premise is usually the same: a large insulated chamber or room is used to balance and control humidity, temperature, and airflow to safely and efficiently bring wood down to an acceptable moisture content. The main advantage of a kiln is that with the increased temperature and airflow—all while carefully maintaining and controlling the ambient humidity—the wood can be dried much more evenly, minimizing any sort of moisture gradient between the outer shell which dries very quickly and the inner core which slowly equalizes moisture with the shell.
Drying defects But kiln drying may also introduce internal stresses into the wood—particularly if an improper kiln schedule is used, or if corrective measures are not employed—resulting in a condition known as case-hardening. This defect is caused when the outer shell begins to dry faster than the core: the shell tries to shrink, but is inhibited by the still-wet core.
If the moisture difference between the core and the shell is too great, the shell can dry in a stretched condition. Later, as the core eventually begins to dry and shrink, the condition is reversed, and the stretched shell prohibits the core from completely shrinking.
In extreme instances of case-hardening, the core can split and check in an irreversible condition called honeycombing. Kiln drying wood at elevated temperatures also has many other secondary effects as well, such as killing powderpost beetles a destructive wood pest in all stages of their development. For most woodworkers, running their own kiln to quickly dry lumber may be impractical or excessive.
In most instances, simply storing project lumber at a targeted humidity level is the best option to ensure it will be at the correct EMC when building time comes. However, in some cases, such as when processing logs or other green wood into lumber, a more meticulous procedure will need to be followed.
Home air-drying tips Process logs in a timely fashion. Bark on whole logs can act as a natural moisture-barrier, and if left unsawn, can contribute to fungal decay and deterioration in some species. A hallmark of poorly processed, do-it-yourself lumber is the presence of spalted or partially rotted wood.
Cut the wood slightly oversized. Remember that wood shrinks as it dries. Seal the ends. In addition to processing logs in a timely manner to prevent stain and decay due to excessive moisture, the opposite is also to be avoided: allowing the wood to dry out too quickly will result in splits and endgrain checking. It is important to remember that moisture escapes from wood about 10 to 12 times faster on the ends than through other surfaces.
Sealing the endgrain forces the moisture to exit in a slower, more uniform manner. Although there are specially formulated endgrain sealers on the market, just about anything will do in a pinch: paraffin wax, polyurethane, shellac, or even latex paint can be used to seal the endgrain surface.
The key is to build up a thick, obstructing film that will inhibit moisture from escaping at the ends of the board. In order to minimize the risk of checking, it is best practice to coat lumber ends within minutes—not hours or days—after coming off the saw. Stack and sticker. Add weight. The lumber at the bottom of the stack is probably weighed down sufficiently by the wood on top of it, but boards near the top greatly benefit from added weight.
Weighing the stack of wood down helps to prevent warping or distortion, which is especially important during the initial drying phase when going from green to an ambient EMC. Neatly and properly stacking, stickering, and weighing wood will go a long way towards ensuring that the drying process will result in flat, stable, and usable lumber. This small stack of buckthorn Rhamnus cathartica half-logs has just been cut, stacked, stickered, and sealed with a water-based wax emulsion coating.
Add heat once EMC is reached. This can be as simple as moving the lumber stack from a garage or shed into a heated basement indoors. A drying cabinet can be nothing more than a simple wood cabinet with an incandescent lightbulb on a dimmer to finely control the light output—which in turn dictates both internal temperature and consequently relative humidity.
Many thermometers both traditional and digital sold by big-box retailers also feature a hygrometer with a somewhat accurate readout of the relative humidity; the ability to know the RH of both the drying cabinet and the wood shop proves to be a helpful and prudent investment.
A good way to visualize the tendencies of wood during drying and shrinking is to picture the arc of the growth rings trying to flatten themselves out. This of course is not actually the cause of the shrinkage, but it serves as a good memory tool to help visualize dimensional changes. This endgrain view of plum Prunus domestica exhibits cupping.
The board was initially cut flat, with the top and bottom originally being parallel. Further machining will be necessary to ensure the board is flat and square. The results of uneven shrinkage vary depending upon the particular shape and grain orientation of the board; flatsawn boards become cupped, riftsawn square stock becomes diamond-shaped, and circular dowels become ovoid.
Additionally, there are a number of warping issues that can occur which are not solely related to uneven shrinkage. In certain cases, a pre-existing flaw is present in the wood itself, which is only brought out and made apparent by the drying process. This can result in defects such as: bow, crook, twist, or a combination of two or more defects simultaneously. Regardless of the specific names that can be applied to distorted lumber, most drying-related warping issues can at least be minimized using a few simple guidelines: Use proper stacking techniques.
As mentioned previously, by far the most important deterrent to warp is the adequate stacking, stickering, and weighing of a lumber stack. Avoid juvenile wood. There is no officially determined width of juvenile wood, usually excluding the first few central growth rings is sufficient , but generally, the further the wood is cut from the pith, the better. Much like the pith itself, juvenile wood is very unstable, and has an elevated rate of longitudinal shrinkage; this increased shrinkage rate pulls against the mature wood and causes it to contract and deform either along the face of the board bow , or along the side of the board crook.
Avoid processing branches or leaning trees. This abnormal wood is called reaction wood, and it can cause a number of unpredictable warping problems during drying.
In softwoods, reaction wood forms on the underside of a branch or trunk, and is called compression wood. Conversely, in hardwoods, just the opposite is true: its reaction wood forms on the topside and is called tension wood. An open shed or outside area with a metal roof over the top is ideal. To dry a quantity of lumber containing 1" and thicker boards from 6" to 10" wide and 6' to 10' long, follow the procedure below to build a proper stack using the materials shown in Figure 3.
Put a sheet of heavy at least 4 mil plastic on the ground to keep moisture away. Then lay out the landscaping timbers to raise the stack off the ground by at least 4" to 6". They need to form a flat surface, as the boards will conform to the timbers as they dry. Next, lay a sticker along each landscape timber.
If the boards vary in length, start the stack with the longest ones. I recommend identifying the species with a tag, so they will be easy to sort after they air-dry. Align the stickers vertically so they transmit the weight of the stack straight down to the ground. Having a second person makes stacking easier, since it allows you to each take an end of the board and set it straight down without moving the stickers.
Go as high as you safely can. I stop at 6'. With a stack that is out in the open, do what you can to keep the rain and sun off, while allowing good air circulation. Whatever cover you use should sit on a layer of stickers to allow air to flow over the top of the stack. If this is a one-time proposition, overlap some scrap lumber on the stack to shed water, and strap or weight it down.
Metal roofing, like the kind you get at a home centers, is better. Then comes the hard part…waiting. The European style involves stacking slabbed wood with one or both edges left natural to reconstruct the log Photo C. This allows the craftsman to select matching grain and create book-matched tabletops. The same drying principles apply to this stacking approach.
Once the stack is assembled, put a couple of ratcheting straps on it to keep it from warping badly. Once a week or so, tighten down the ratchet straps. They tend to loosen some as the wood dries and shrinks. The top slab protects the stack from rain, and the edges naturally shed water. Unlike conventional stacking, it is not an efficient use of space.
Though wood air-dries one year for each inch of thickness, this does not take into account drying rates based on the season, climate, and time of year. Air-drying only brings the wood down to an MC that corresponds to the average outdoor relative humidity, though it does respond to seasonal humidity changes.
After a long, dry summer, it may pick up moisture in the fall. Species such as walnut and poplar have a porous structure that allows them to dry more quickly than white oak or maple. If the design allows for shrinkage without damaging the wood or causing joints to loosen, you can use air-dried lumber.
You can do this at any point in the drying process. Drying wood in the shop, however, requires space, a fan to circulate air, and monitoring the MC. For accurate monitoring, invest in a good moisture meter when air-drying wood see the one I used in the buying guide. It lets you keep track of the MC of the wood you dry as well as the wood you buy. The better ones compensate for temperature and species, and have wired probes for monitoring MC at several places in a lumber stack.
These wires are left in the boards for the duration of the drying process. Pinless meters are more expensive, but take a reading by holding one against the wood. They lack probes that could mar the wood. Insects cause major damage to lumber, often reducing beautiful boards to something resembling Swiss cheese.
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