Air- And Shed-drying Lumber - OSU Extension Catalog
EM 8612-E Reprinted October 2007tThere are several reasons to dry solidwood products: Drying wood before use helpsprevent staining and decay whilein service.Drying wood to the averagemoisture content1 (MC) whereit will be used ensures minimaldimensional change (shrink orswell) while in use.Dry wood weighs less and isless expensive to ship than greenwood. As wood dries below its fibersaturation point (moisture contentof about 25 to 30 percent), moststrength properties increase.For more information on therelationship between wood andmoisture, see the OSU Extensionpublication Wood and MoistureRelationships (see back page).Wood can be air-dried only, kilndried only, or air-dried to a certainMC and then kiln-dried. For example,green 4/4 white oak can take morethan a month to kiln-dry, while airdried 4/4 white oak can be kiln-driedin 1 to 2 weeks. For most commercialkiln operators, it is less expensive tohave inventory on the air-dry yardthan to do all drying through the kiln.Air- and Shed-drying LumberJ.E. Reeb and T.D. BrownThe process of drying wood is thesame for air- and kiln-drying, but inkiln-drying you have much greatercontrol over air velocity, temperature,and humidity. Controls are much lesswhen air-drying lumber.Air-dryingAir-drying means stacking lumberand exposing it to the outdoors.Final MC is determined by the airtemperature, relative humidity, anddrying time.Depending on outside conditionsand lumber species and size, airdrying to a desired MC can take fromseveral months to almost a year.Wood stored outdoors and undercover will dry to an approximatemoisture content of 12 to 14 percentin western Oregon and 8 to 10 percentin eastern Oregon.When air-drying wood, you muststack the wood properly to ensureadequate air circulation, and you musttest it frequently to monitor moisturecontent. Certain controls can makeair-drying more efficient. Theseinclude orientation and layout of thestack, stacking methods, and coveringthe stack; all are discussed below.Air-drying of wood begins assoon as the tree is cut. If the wood isto be used for furniture, moulding,millwork, or other high-value uses,take care to prevent degrade. If youare working with logs of speciesJames E. Reeb, Extension wood productsspecialist, and Terence D. Brown, formerExtension wood products specialist; both ofOregon State University.Technical terms are printed in bold at theirfirst use and are defined in the glossary onpages 6 and 7.1Figure 1.—A lumber stack with aconcrete block foundation and correctsticker alignment. A roof protects thelumber from sun and rain.
prone to checking, such as oak, applyan end coating as soon as possible,preferably in the woods before thelogs are hauled.Orientation and layoutof the stackThe orientation and layout of thestack(s) of lumber play an importantrole in how lumber air-dries.Construct the air-dry yard ongently sloping ground so water doesnot pool under stacks or in alleyways.Lumber stacked over a surface wherewater cannot pool, such as concreteor asphalt, dries faster than lumberstacked over bare or vegetationcovered ground.Vegetation beneath the stackexposes the bottom layer to air witha higher moisture content. Therefore,never stack lumber over vegetationcovered ground.Wind is not needed to force airthrough the stack. Air circulationcan develop by natural convection.Warm, dry air enters the sides andtop of the stack. As the dry airmoves over the lumber, it evaporatesmoisture from the surfaces. Throughevaporation, the air becomes cooler,moister, and thus heavier. The heavierair moves toward the bottom of thestack. If the prevailing wind movesfreely, the cool, moist air is blownaway and is replaced with warmer,drier air. Therefore, increasingthe height of the foundation, thusallowing more space under the stack,will increase the drying rate.You can use orientation and layoutin several other ways to increase thedrying rate: Use shorter and narrower stacks tofacilitate air access.Stack lumber away frombuildings, trees, or other objectsthat block the wind. Orient rows of stacks to allowprevailing winds to blow moredirectly under foundations.StackingFigure 1 (page 1) shows a stackof lumber properly built for airdrying. This example uses concreteblocks as a foundation, but treatedtimbers or old railroad ties also couldbe used. (Caution: Wood preservedwith chemicals may stain lumber itcontacts.)Ideally, a bottom support bunk, orbolster, should be under every row ofFigure 2.—Step-out methodof piling random-lengthlumber.2stickers. This is especially importantfor thin lumber, which is more likelyto sag.Use stickers that are dry and ofuniform size. Stickers should beenough wider than they are thick sothey are not accidentally placed onedge between a layer of lumber. Oneinch thick stickers commonly areused for air drying.Proper sticker alignment, resultingin proper support for the lumber,is important in reducing warp asthe lumber dries. Proper stickerplacement also allows air to circulateevenly across the surfaces of thelumber and promotes a more uniformdrying rate.Place stickers as far apartas practical to ensure good aircirculation. However, propersticker distance depends on the size(especially thickness) of the lumber.Place stickers farther apart for thickerlumber, because it does not need asmuch support as thinner lumber.Generally, a sticker distance ofabout 18 to 24 inches is sufficient forlumber of almost any size. However,some hardwoods, such as elm, shouldhave stickers every 12 inches.It is important to place stickers atequal distances and straight acrossa layer. Use a sticker at each end ofeach layer for support. Align stickersone on top of the other.It is best if lumber pieces in theentire stack are the same thickness,because the time required to air-drylumber to a target MC depends a loton thickness. Two-inch lumber cantake three to four times as long to airdry to a certain MC as 1-inch lumberof the same species.A thick board in a course cancause nearby boards to warp due toinadequate restraint of these boards.So, minimally, each layer shouldconsist of lumber as nearly equal inthickness as possible.It is best to stack lumber of thesame length together. If you stackAir- and Shed-drying Lumber
Figure 3.—Box piling lumber of random lengths.long and short lengths randomly,the ends of the longer boards mayoverhang. This situation increaseswarping, end checking, and splittingand can lead to mechanical damageand safety concerns because forkliftsand other machinery could run intothe overhanging ends.If you must stack different lengthsof boards together, two suggestedmethods for stacking are step-outand box piling.The step-out method This placesthe longest lengths at the bottom, withthe next longer boards placed on thenext layer, and so on until the stack isfull (Figure 2). Place stickers acrosseach course, supporting the ends ofeach board to minimize warping. Thismethod does not allow you to build aroof or cover over the stack.Box piling This arranges lumberso the length of the outside boards ineach course is equal to the full lengthof the stack (Figure 3). Place otherfull-length boards near the middle ofthe stack across a course.Arrange the shorter boardsalternately with their ends evenwith each end of the stack. If younumbered the short boards, the endsof all even-number boards would beeven with one end of the stack, andthe ends of all odd-number boardswould be even with the opposite endof the stack.You can butt the ends of exceptionally short boards together as longOregon State University Extension Serviceas their combined length does notexceed the stack’s length. Althoughunsupported ends of short boards maywarp, this is the best way to supportand hold down different lengths oflumber in the same stack.Box piling is the preferred wayto stack lumber of different lengths.Remember, lumber pieces should bethe same thickness, and it is best tostack lumber of the same length.In Figure 1 (page 1), thicker andlonger pieces are used above thetop layer to support a cover. A roofextends over the lumber by 2 to3 inches on all sides to protect thelumber from precipitation and directsun. It may be slanted so precipitationruns off. In this case, 4- by 6-inchtimbers (4 to 6 inches longer than thestickers) support the roof.Weight is needed to hold theroof in place. The extra weight alsohelps keep the top layer of lumberfrom warping as it dries. In Figure 1,cinder blocks on the roof add weight.The blocks are aligned directly abovethe stickers.Controllingthe drying rateRemember the fundamental ruleof drying: Quality depends on therate of drying. You must achieve abalance between drying lumber tooslowly, which would result in stain ordecay, and drying lumber too quickly,which would result in checking. Ifyou weren’t worried about defects,you could dry wood in a matter ofhours in an oven.In Oregon, especially east ofthe Cascades, lumber can air drytoo fast. A temperature of 90 F and15 percent relative humidity yieldsan equilibrium moisture content ofless than 4 percent. A kiln operatorwould not expose green lumber tosuch harsh drying conditions.In western Oregon, on the otherhand, humidity often is too high toeffectively air dry lumber duringthe fall and winter. The lumber rewets by either direct precipitationor high relative humidity. However,lumber properly air dried through thesummer should reach an MC of 12 to14 percent by fall.Uncontrolled air drying may drylumber too fast. This causes dryingdefects, most commonly surface andend checks. These defects occurduring the initial drying period, whenwood is the wettest.Drying stresses develop becausewood shrinks by different amountsin different directions and becauseshrinkage affects outer fibers beforeinner fibers, thus creating a moisturegradient between the lumber’s coreand shell. (See OSU Extensionpublication Wood and MoistureRelationships, on back page.)Surface checks form as themoisture gradient develops if thelumber surfaces dry too quickly.Thick, wide lumber is moresusceptible to surface checking thanthin, narrow lumber. Flatsawn lumberdries faster and is more susceptibleto surface checking than quartersawnlumber (Figure 4, page 4).Surface checks, especially inhardwoods, can close in the laterstages of drying. This occurs whenthe stresses reverse (the core becomesdrier than the shell), and the lumbershell changes from tension tocompression. Although these closedchecks cannot be seen, they cause3
problems for end uses, especially ifhigh-quality finished surfaces areneeded for products such as interiortrim, moulding, cabinets, andfurniture.End checks usually are in thewood rays on end-grain surfaces.End checks occur because moisturemoves much faster in the longitudinaldirection (through the ends of theboard) than in either of the transversedirections (through the sides of theboard). The ends of the board (orlog) dry faster than the middle, andstresses develop at the ends. Thesestresses can cause checks and warp todevelop.Direct sun can have a dramaticimpact on the drying rate. Lumber indirect sun can dry faster than lumberinside the stack and on the side of thestack away from the sun.If the lumber in direct sun driestoo fast, you can use covers orbarriers to protect the wood from thesunlight. Several commercial coverseffectively block sunlight but allowair movement through the stack.Maximum safe drying rates havebeen established for some hardwoodspecies (Table 1). Some hardwoods,especially oaks, have low maximum values for rates of moisture lossper day (about 1 to 2 percent). Theseare maximum per-day values,not values averaged over longerperiods.If drying defects occur, thereare several ways to slow thedrying rate: Yellow birch16.1Cherry5.81Chinkapin2.0–3.02American elm10.41Soft maple1Make the stack larger(especially wider).13.8Bigleaf maple8.0–10.02Hard maple6.51Partially block the wind.Eastern red oak1 Orient rows of stacks soprevailing winds do notblow directly under thefoundations.For lumber, such as thickoak boards, that is difficult todry without causing seasoningchecks, several additional stepsmay be necessary.You can apply a coating tothe ends of the lumber to retardthe drying from these points.End coatings usually are waxbased. Apply end coatings as soonas possible because they are not aseffective after the lumber starts todry. You also can cover the ends ofthe lumber or the entire stack withMaximum daily rateof moisture loss (%)SpeciesBuild the stack of lumberover crushed rock or bareground rather than asphalt.Figure 4.—Annualgrowth rings. Aquartersawn board(left) shows theannual rings’ edgeson its broad face.The flatsawn board(right) shows thesides of rings.4Table 1.—Safe drying ratesof some hardwood 4/4 lumber.California black oak2Eastern white oak1Oregon white oak2Walnut13.82.0–4.02.52.08.2Empirically established drying rates forsome eastern hardwoods (Wengert, 1980).2Estimated drying rates based on anatomicalsimilarities with other hardwoods.1burlap. Polypropylene fabric, orshade cloth, has been used to coverhorticultural and agricultural cropsfor many years. More recently, thisproduct has been used successfully toslow the drying of lumber and reducechecking. The use of end coatings,burlap, polypropylene, and othermaterials to slow the drying rate forcertain species and sizes of lumber iscommon among commercial wooddrying firms.Drying shedsIf you are air drying large amountsof lumber, you can use a pole-typeshed to achieve greater control overthe drying process. Sheds allow morecontrol since one or more sides canbe blocked off, slowing the dryingprocess. In addition, the lumber isbetter protected from precipitationand direct sun.Drying sheds can be very simplein their construction. They can bemade more complex by adding wallsAir- and Shed-drying Lumber
that can be raised or lowered andby adding fans to increase air flowthrough the building and to enablemore control to the drying process.You can block the sides of theshed and install fans at one end.Leave the other end open. Runthe fans when you want increasedcirculation and shut them off todecrease circulation.For wood species that have atendency to check when drying toofast, such as oaks, run the fans whenthe exterior humidity is high and theair temperature is low. Turn fans offwhen the humidity is low and thetemperature is high. This processslows the drying rate at the beginning,when lumber with a high MC is mostsusceptible to checking.After the wood has dried to belowabout 22 percent MC, you can turnon the fans when the temperature ishigh and the humidity is low. No newsurface checking will occur once thewood has reached this low MC.When the humidity is high, turnthe fans off to avoid reintroducingmoisture into the lumber. Because noheat is added with this type of drying (sometimes referred to as fanpredryers), the final MC is determined by outside ambient temperatures and relative humidities, just asin air-drying but with more control.Determiningmoisture contentWhen air-drying lumber, you canmonitor the lumber for staining orchecking to determine whether it isdrying too slowly or too quickly. Youthen can use some of the techniquesin Table 2 (page 7) to either slow orspeed the drying.However, most stains and allchecks are permanent once theyappear. A better way to track MC lossis to use a moisture meter, and thebest way is to use the sample boardmethod.Oregon State University Extension ServiceMoisture content is the totalamount of water in a given pieceof wood. The MC of wood usuallyis described as the ratio of theweight of the water to the weight ofthe wood after the wood has beenoven-dried. Although 100 percentusually signifies the total amount ofsomething, the MC of wood can begreater than 100 percent because thewater can weigh more than the wood.Moisture content for green(undried) lumber can range from35 percent to more than 200 percent.The higher the initial MC, the longerit will take to dry the wood.Sample boardsYou can use sample boards tomonitor the MC of lumber while itis drying. For expensive woods susceptible to drying defects, such asoaks, sample boards are especiallyimportant during the initial dryingphase.Sample boards should be representative of the moisture content ofthe lumber being dried. Generally, thewettest lumber has the highest riskof degrade, so sample boards shouldrepresent the wettest lumber.The wettest lumber usually isthe most recently cut, or the widest,or the thickest. Also, quartersawnlumber tends to be wetter thanflatsawn lumber. Select the largestnumber of samples from the slowestdrying material.Referring to Figure 5, preparesample boards as follows.1. Select the lumber to be used.2. Cut a 30-inch sample board.3. Cut two l-inch sections from thesample board. Avoid areas nearknots or within 12 inches of theends of the board.4. Number the two 1-inch sectionsyou cut.5. Immediately weigh the l-inchsections to an accuracy of 0.1 gram ( 0.035 ounces).Record the weight directly on thesection with a marker pen.6. Weigh the sample board to anaccuracy of 0.05 kilograms( 0.11 pounds). Record theweight directly on the board witha marker pen.7. End coat the sample board; adouble coating is best.8. Place the sample board in thelumber pile where it will dry at thesame rate as the rest of the lumber.9. Dry the l-inch sections in an ovenat 215 to 218 F (103 C), justabove the boiling point of water.Dry the wood about 24 hours; becareful not to burn or char it.10. Weigh the l-inch sections againand record the weights.11. Repeat steps 9 and 10 until youget the same weight twice in arow. The wood now is oven dry(OD), sometimes referred to asbone dry.Figure 5.—Method of cutting and numbering kiln samples and moisture contentsections.5
12. Use the following equation todetermine the wood’s MC percent:Weight of woodbefore dryingOven-dry weight– 1 x 100For example, if the wood weighs84 grams before drying and60 grams after drying, theequation is:8460If the water and wood weighexactly the same, the MC is100 percent. If the water weighsmore than the wood, the MC isgreater than 100 percent; if thewater weighs less, the MC is lessthan 100 percent.13. Add together the MC percent ofthe two sections and divide by 2to determine the average MC ofthe wood:2 average %MCFor example, MC1 (fromstep 12) is 40 percent. Assumethe moisture content for MC2 is46 percent:40% 46%2 43%14. Calculate the oven-dry weightof the sample board using theaverage MC percent you foundin step 13 and the weight of thesample board from step 6.Wet weight (step 6)100 %MC (step 13)x 100 ODFor example, if the sample boardweighs 3.84 kilograms:3.84100 43x 100 2.69 kg15. Write this calculated oven-dryweight on the sample board andreturn it to the lumber stack.6Current weight (step 16)Calculated OD weight(step 14)– 1 x 100For example, if the new weight ofthe sample board is 3.21 kg:3.212.69– 1 x 100 40%%MC1 %MC216. Periodically reweigh the sampleboard to obtain a new, currentmoisture content.– 1 x 100 19.33%This procedure lets you monitorhow fast the wood is drying. SeeTable 1 (page 4) for maximumsafe drying rates of variousspecies.Moisture metersYou can use a hand-held moisturemeter to determine maximum dailyMC loss and to help determine finaltarget MC. However, moisture metersare not as accurate as the sampleboard method. For moisture contentsgreater than the fiber saturation point(about 30 percent MC), moisturemeter accuracy is questionable.Remember, wood is mostsusceptible to degrade, includingsurface and end checks, as it starts todry from the very wet stage. If youdo not use sample boards, you shouldpay very close attention when dryingspecies susceptible to checking, suchas oak, during the early drying stage.If surface or end checking occurs,decrease the drying rate.The most common type of handheld moisture meter is the resistance(or conductance-type) meter, whichhas pins that penetrate the woodsurface.Another type of hand-heldmoisture meter is the dielectric powerloss meter, which has smooth surfacesand does not penetrate the wood.Because of this design, dielectrictype meters are used in-line at woodproducts mills to monitor lumber,veneer, and other products for highmoisture content.For accurate measurements,you must apply temperature andspecies corrections to both types ofmeters. Manufacturers supply thesecorrections.Problemswhen air-drying Lumber is susceptible to fungi,mold, and insect infestation whileon the yard. Temperatures are nothigh enough to kill fungi, mold, orinsects.Lumber that air-dries too quicklycan check, split, honeycomb, andwarp.Lumber is susceptible to chemicalreactions and bacteria, and bothcan cause stains.Lumber can become “weathered”from dirt and other contaminants. Temperatures are not high enoughto set the resin in highly resinousspecies.Table 2 summarizes techniquesto help reduce checking, warping,staining, and decay during air drying.GlossaryBolster—A square piece of wood,usually 4x4, placed betweenstickered packages of lumber toprovide space for the forks of a lifttruck.Bone dry—Wood at zero moisturecontent. Not a natural state forwood. As soon as bone-dry woodis exposed to air, it will take inmoisture.Bow—A form of warp. Bowdescribes a deviation flatwise froma straight line drawn from end toend of a board. If the board is laidflat on a wide face, the ends of theboard will be off the ground.Check—Lengthwise separationof wood fibers that extendsacross the annual growth rings.Air- and Shed-drying Lumber
Table 2.—A guide to reducing checking, warping, staining, and decay.A relatively slow initial drying ratereduces checking.Proper support and restraintreduce warping.Fast surface dryingreduces staining and decay.Do the following:Do the following:Do the following:Space stacks no more than 2 feet apart.Use close spacing between stickers,such as 12 to 16 inches.Provide more space between piles, suchas 6 feet.Avoid different board thicknessesacross a layer.Keep yard clean and avoid blocking airspace below piles.Use wider stacks or a double stack on asingle foundation.Butt lumber in each course edge toedge as closely as possible, especiallyin the upper layers.Use thinner stickers (0.5 or 0.75 inch)Use polypropylene or shade cloth toprotect lumber from direct sun.Use box piling if you stack differentlengths of lumber in a stack.Use end coatings for logs and lumber.Commonly caused by stressesduring drying. Surface checksoccur on flat faces of lumber,and end checks occur on endsof lumber, logs, and other woodproducts.Crook—A form of warp. Crookdescribes a deviation edgewisefrom a straight line drawn fromend to end of a board. If the boardis laid on its edge (narrow face),one or both edges will be off theground.Cup—A form of warp. Cup describesa troughlike shape in which theboard edges remain approximatelyparallel to each other.Equilibrium moisture content—Thebalance of moisture content woodattains in response to the relativehumidity and temperature of thesurrounding atmosphere.Fiber saturation point—The stage in thedrying or wetting of wood whenthe cell walls are saturated withbound water and the cell cavitiesOregon State University Extension ServiceAlign stickers exactly above eachother. Support both ends of eachboard with a sticker.Use stickers of uniform thickness.Use a roof that extends past the pileby several inches on all sides.Use box piling if you stack differentlengths of lumber in a stack.Reduce the width of the stack.Increase space between lumber acrossa course.Use a chemical dip, which can retardstaining and decay.are free of liquid water. Fibersaturation point for most woodspecies is at moisture contents ofabout 25 to 30 percent.Relative humidity—The ratio of thevisible on the surface, that occurmost often in the interior of thewood, usually along the woodrays.Split—Separation of wood fibersHoneycombing—Checks, often notMoisture content (of wood)—Theweight of the moisture in wood,usually expressed as a percentageof its oven-dry weight.Natural convection—A circulatorytransfer of heat due to warmerair rising and cooler, denser airsinking.Oven dry—See bone dry.Pile—Lumber stack. Stackinglumber layer by layer, separatedby stickers on a supportingfoundation or stacking stickeredpackages one above the other on afoundation separated by bolsters.amount of moisture in the airto the maximum amount ofmoisture the air could hold at thattemperature.along the grain, forming a crack orfissure. Splits may extend partiallyor completely through the wood.Stickers—Solid or laminated woodstrips used to separate lumber.Typical sizes are 0.5 to 1 inchthick and 1 to 2 inches wide.Use 1-inch thick stickers for airdrying.Twist—A form of warp. Twistdescribes a lengthwise “twisting”of a board in which one cornertwists out of the plane of the threeother corners.Warp—Distortion in lumber and otherwood products, causing departurefrom its original plane. Commonforms of warp are bow, crook,cup, and twist.7
For more informationUSDA Forest Service, ForestProducts Laboratory. Visit thePublications section s/1-publication-list.html —and search on topics ofinterest.Other publicationsBond, B., 2006. Design andOperation of a Solar-HeatedDry Kiln, Publication 420-030.Virginia Polytechnic Instituteand State University ExtensionService.Peck, E.C., 1962. Drying 4/4 RedOak by Solar Heat. ForestProducts Journal 12(3):103–107.Plumptre, R.A., 1983. SomeThoughts on Design and Controlof Solar Timber Kilns. WoodDrying Workshop of IUFRO,Division V, Conference, Madison,WI.Reeb, J.E., 1995. Wood and MoistureRelationships, EM 8600. OregonState University ExtensionService. 8600.pdfSimpson, W.T., ed., 1991. Dry KilnOperator’s Manual, AgricultureHandbook 188. USDA ForestService, Forest ProductsLaboratory, Madison, WI.Wengert, E.M., 1971. Improvementsin Solar Dry Kiln Design,Research Note FPL-0212. USDAForest Service, Forest ProductsLaboratory. http://www.fpl.fs.fed.us/documnts/fplrn Then go tofpl rn212.pdfWood and How to Dry It. 1980. FineWoodworking 22:56–59.Rietz, R.C. and R.H. Page, 2003.Air Drying Lumber: A Guideto Industry Practices (USDAForest Service, AgricultureHandbook 402). 1995 Oregon State University.This publication may be photocopied or reprinted in its entirety for noncommercial purposes. Produced and distributed infurtherance of the Acts of Congress of May 8 and June 30, 1914. Extension work is a cooperative program of Oregon StateUniversity, the U.S. Department of Agriculture, and Oregon counties. Oregon State University Extension Service offers educationalprograms, activities, and materials without discrimination based on age, color, disability, gender identity or expression, maritalstatus, national origin, race, religion, sex, sexual orientation, or veteran’s status. Oregon State University Extension Service is anEqual Opportunity Employer. Published September 1995; reprinted October 2007.
Air- and Shed-drying Lumber J.E. Reeb and T.D. Brown EM 8612-E Reprinted October 2007 The process of drying wood is the same for air- and kiln-drying, but in kiln-drying you have much greater control over air velocity, temperature, and humidity. Controls are much less when air-drying lumber.
A stack of uniformly thick and well-piled lumber is shown in figure 5-lb. Figure 5-1—(a) Stacking lumber of different thicknesses in the same stack results in warping of lumber and de-formation and breakage of stickers. (b) Lumber of uni-form thickness and stickers remain flat during drying.
Solar Drying Recent efforts to improve on sun drying have led to solar drying. Solar drying also uses the sun as the heat source. A foil surface inside the dehydrator helps to increase the temperature. Ventilation speeds up the drying time. Shorter drying times reduce the risks of food spoilage or mold growth. Pasteurization
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Me- EMC, %db . Mo – Initial moisture content, %db . K – drying constant . θ - time, hour . Deep bed drying All grains are not fully exposed to the same condition of drying air . Grain fed at the top & move downward in a zig-zag path where it encounters a cross flow of hot air
Western Lumber Co. Western 1-'ine Association Western Oregon Lumber Co. Westport Lumber Co. West Waterway Lumber Co. Willamette Iron and Steel Works Wilson, A. K. Winchester Bay Lumber Co. Wind River Lumber Co. Wisconsin Department of State 3. Unidentified. Inclusive dates 1936 1920 1937 1922
groups and reflect the fact that wood is an ortho-tropic material. 2.7 Dry lumber--Lumber of less than nomi-nal 5-inch thickness which has been seasoned or dried to a maximum moisture content of 19 per-cent. Note: Lumber of nominal 5-inch or greater thick-Lumber . Lumber . 2 .
2 · FREEZE DRYING In our RAY freeze dryers, frozen products are dried at temperatures below -18 C. No thawing of the product takes place and its quality is preserved. Pressure Torr Water phase diagram Temperature 1000 760 100 10 4.6 1 Hot air drying Vacuum drying Product (Room Temperature at sea level pressure) Freeze drying Triple .
P 4 418.668 P 4 419.989 P 5 418.186 P 5 419.227 P 6 418.973 P 6 419.684 P 7 419.379 P 7 420.751 P 8 420.141 P 8 420.065 P 9 419.532 P 9 421.259 P 10 418.643 P 10 421.386 P 11 418.719 P 11 418.846 P 12 416.763 P 12 419.887 P 13 414.782 P 13 418.363 P 14 P 14 P 15 P 15 P 16 P 16 P 17 P 17 P 18 P 18 P 19 P 19 Test Sample j 2 Test Sample j 3 Reading Points Reading Points Reading Points Test Sample .
