The most commonly referenced "heaviest wood", lignum vitae (Guaiacum officinale), has a specific gravity of 1.05 when green, which makes its weight about 1365 kg/m3, or 85 pounds per green cubic foot. Off the top of my head, Id say average for most woods is .4 -9 specific gravity. Specifically, it is the mass in a unit of volume. You must have JavaScript enabled in your browser to utilize the functionality of this website. /Type /XObject
Density is expressed in the units of mass divided by volume, such as grams per centimeters cubed (g/cm3), kilograms per meter cubed (kg/m3), or pounds per cubic foot (lb/ft3). All Rights Reserved. Wood density and specific gravity are terms that are often used interchangeably, although they are slightly different concepts. With such a wide disparity between specific gravity values, its not hard to see how confusing this measurement can become when no qualifyinginformationaccompaniesthe value. Once moisture content goes below 30%, however, all the free water has been released through evaporation, and the bound water begins to be chemically driven from the wood substance. Professional builder and craftsman Jordan Smith explains: Specific Gravity is a shorthand way of saying how dense a material is as compared to water. Edited by F.F. BTU charts that I can find on the net give varying values, sometimes significantly. In the case that the value is not available in our database or custom basic specific The density of wood differs depending on tree species and tree growth environment. A woods density or specific gravity also affects how it holds a fastener. Since the weight is always based on the ovendry value, it tends to produce anartificiallylow impression of specific gravity. Such a combination is a real-world impossibility: its useful within the scientific community, but is very confusing for the woodworking community. These are BASIC specific gravity numbers, so please take this into account if trying to calculate average dried weight. We are constantly working on the content of our website and are always eager to add new features. Let me ask, would a piece of wood thats not dried in an oven, go to its basic (0 mc) specific gravity over time?? A similar situation exists between earlywood and latewood. Then its original moisture content would have been (100-40)/40, or 150%. per cubic foot), Considered by some to be the original ebony: 1.08 g/cm3 (67 lbs. With the specific gravity around 1.5, solid wood "substance", or lignocellulose as it is commonly called today, weighs around 1500 kg/m3 (93.6 lb/ft3), at theoretical mostno air, water, or other fluids in cell pores, which would decrease the weight of the wood per unit of volume. Did I miss something? [arve url=https://youtu.be/6XAJyj9Au6Y /]. To keep it simple, I calculate a Low Range estimate and a High Range estimate for moisture content as 1/3 and 2/3 of the way between the stated values of heartwood and sapwood moisture content. Classes include professionally produced videos taught by practicing craftspeople, and supplementary downloads like quizzes, blueprints, and other materials to help you master the skills. Canarium oleosum (aka Grey Canarium). >>
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Learn more. This leads us also to the understanding that sapwood, with its higher moisture content in the field, often weighs more than heartwood. JavaScript seems to be disabled in your browser. It can't, of course. Learn all about the properties of wood and how wood is used in construction in the. Jordan suggests thinking of a piece of wood marked with two points. As 1000kg of pure water @ 4C = 1 cubic meter, those materials under 1000kg per cubic meter will float; more dense materials will obviously sink. Hardwoods vary by species, and on average the moisture content in sapwood is only slightly higher.
See All Pest, Disease and Weed Identification, See All Beer, Hard Cider, and Distilled Spirits, See All Watershed Protection and Restoration, See All Community Planning and Engagement, Specific Gravity and Other Properties of Wood and Bark for 156 Tree Species in North America, Alternative Energy Credits for a Renewable Energy Market, BarkThe Issue Facing the World's Wooden Pallet Industry. Therefore altitude has no influence on density. What is the range of specific gravity if wood generally????? per cubic foot), With cells full of water, balsa lumber is very soft and light, with a density of only 0.11 gm g/cm3 (around 7 lbs. Learn all about the properties of wood and how wood is used in construction in the MT Copeland course on Wood Materials.
The calculation becomes: Oak-Hickorygreen = 590 * (1 + 0.71) = 1009 kilograms/m3 , or 63 pounds/ft3. Accordingly, specific gravity measurements referenced in woodworking will usually be a pairing of green weight and green volume, 12% MC weight and 12% MC volume, and so forth. Im also interested in getting photos of completed wood projectsespecially of obscure or lesser known woods. This technique works well for all wood species. He learned to build and weld while working on the farm with his grandad, and after earning a degree in Welding and Materials Engineering, he spent the next 10 years working in the heavy construction building everything from robots to ships to offshore oil rigs before transitioning to residential construction.
/Subtype /Image Specific gravity was calculated with the recommended formula: Wg= Wd(1 + M/100) to desired moisture content SMC , it is possible to calculate the What we find is that there is a functional relationship between the specific gravity of a wood and the moisture content it can attain; in other words, at a certain point, the density of the wood limits how much moisture it can take in. The higher the number, the more dense the wood. Donating wood samples and pictures of wood itemsIf youve got a new or unusual wood species that isnt on the site, please consider sharing it with the rest of us! Earlywood cells, formed in the fast-growing early weeks of growth when moisture movement is at its maximum, are necessarily larger with thinner cell walls to allow higher flow volume. If we use 80% as the moisture content again (it isn't listed on the Wood Handbook table 4-1), our estimate of live oak's green weight is: Live Oakgreen = 800 * (1 + 0.8) = 1440 kilograms/m3, or 90 pounds/ft3. from green state to oven-dry moisture content (S0). Sea level vs. mountains? Some types of wood are more suitable for construction than others, depending on their physical propertieswhich include density, texture. All of Timberaid.com's content is provided as is, without warranty of any kind. Where:Wg is the wood gravity. Gb . u-]`m8Ps: UM hHq:vd&% Now, suppose that original sample had weighed 100 grams. This is great. Wood specific That is because the cellular structure of wood is "full" of what is called "bound water", the water chemically bonded to the wood. Hardwood and softwood are distinguished in terms of their reproduction: hardwood comes from deciduous trees, which produces seeds with a covering (think walnut, maple and oak); while softwood comes from gymnosperm trees, which have needles and produce cones (think conifers such as spruce and pine). stream Again a table from the 2010 Wood Handbook is helpful. The basic difference between the two classifications is not in their actual hardness. A better way to state our expected green weight of oaks and hickories would be to use estimates based on variation around our mean estimates. There is of course no obligation, but if youd like to give back and ensure that the project continues to grow, consider supporting me on Patreon. You are commenting on the very page of the article look up. Entering your postal code will help us provide news or event updates for your area. %3.1 In addition to the variety of measurements used in botany, woodworkers also use various standards to gauge specific gravityusually based on real-world wood samples. t$"`5X#vchW\h9nDp-ggxvTB6,p4x(** and both are used in different types of construction projects. Many thanks for any help you can provide! Many thanks for such a wonderful site. If its less than oneand most wood is less than onethen its going to float.. In order to calculate a woods bending strength, we have to determine a measurement called the Modulus of Rupture, frequently abbreviated as MOR. %PDF-1.5 % How much does wood weigh? Thank you, Eric. Press on the wood until it breaks, Jordan says. First, that crazy moisture content calculation that confounds so many beginning wood science students. For example, for red mallee burl, you list a Janka hardness of 2,490 lbf based on specific gravity, but I cant tell whether youre using .79 or 1.05. specific gravity varies depending on moisture content. Download the excel spreadsheetto run your own calculations. Terms and Policy. Wood Handbook: Wood as an Engineering Material. And as you can imagine, not every wood is the same. Mass is constant everywhere in the universe. I use it all the time. Wood: Its Structure and Properties. %PDF-1.5 Not really practical or helpful in most instances. The way we reach that measurement is to calculate the ratio between an oven-dry or air-dried mass of wood (that is, the lightest it will ever get) divided by the green volume of the wood (when its freshly cut and has its largest possible water volume) to find its moisture content. per cubic foot), An evergreen perennial, technically a grass: .38 .85 g/cm3 (23.72 53 pounds per cubic foot), Also known as a linden or tillia, its well-known as a light, low-density choice for woodworkers: .32 g/cm3 (20 pounds per cubic foot). /BitsPerComponent 8 But there most certainly is a strong relationship between specific gravity and hardness in wood. Get the latest updates about new courses, special trainings, resources, and more. Actual woods, the amazing composite of cell matrix in infinitely different shapes, sizes, and arrangements, much like a sponge made of lignocellulose, have much lower specific gravity than the theoretical maximum due to the amount of space in the matrix filled with air and water. That is when sg(12%) is most commonly used.). K@G]invL$% #Y9+0ckf;A Wood also contains measurable quantities of organic "extractives" such as such as terpenes, resins, and polyphenols such as tannins, sugars, and oils. Essentially, it is the measure of the strength of a piece of wood loaded with a block perpendicular to the grain until it breaks. We will use the mass of one cubic meter for mdry, and for MC we have a choice: we could plug in an assumed moisture content, one taken from a green sample, or one taken from reference. Some types of wood are more suitable for construction than others, depending on their physical propertieswhich include density, texture, strength, hardness, stiffness, moisture content, potential for shrinkage, deformation, splitting, and flammability. The second number is meant for woodworkers, and is simply a snapshot of the woods specific gravity at 12% MC, (that is, both 12% MC weight and volume). Since water conveniently weighs about 1 g/cm3 , variable with temperature, specific gravity was derived as an index metric to state the weight of other substances relative to water. A rare wood with a density as high as 1.42 g/cm3 (88 lbs. As growth slows, the later cells formed take on a denser form with thicker cell walls and smaller cell lumina. per cubic foot), a small South American tree related to mesquite: .98 g/cm3 (61 lbs. The first number is the basic specific gravity, based on the botanical standard of ovendry weight and green volume. Hello. /Filter /FlateDecode The density of pure water is also 62.4 lbs/cu.ft (pounds per cubic foot) and if we know that a sample of apple has a sg of 0.73 then we can calculate that its density is 0.73 x 62.4 = 45.552 lbs/cu.ft. https://www.fpl.fs.fed.us/documnts/fplrp/fpl_rp643.pdf. In other words, the specific gravity of wood does not change in wood that is above 30% moisture content. 1981. The point at which it snaps is the modulus of rupture, or the measure of the amount of weight you can place on a piece of wood before it breaks. but only based on oven-dry mass movendry . Also, if you have green moisture content data on species outside of North America, and you feel like sharing that data, please send it on and I will add those species with the appropriate calculations to the spreadsheet. Together, the amount of ash and extractives in wood can vary from trace amounts to 30% and therefore affect the weight of wood differently according to species. Having done that, we find that the lowest low range estimate is for sand hickory, at 56%, and the highest high range estimate is 85% for water hickory. Wood of course, is comprised of cells, of which only the cell walls have the specific gravity stated above. In my experience, specific gravity is without a doubt the single most abused and vaguely used term in woodworking terminology. Wood possesses great impact resistance. endstream endobj 3 0 obj 1636 endobj 4 0 obj<>>> endobj 5 0 obj<> endobj 6 0 obj[8 0 R 10 0 R 12 0 R 14 0 R 16 0 R 18 0 R 20 0 R 22 0 R 24 0 R] endobj 7 0 obj 2108 endobj 8 0 obj<>stream Table 1. Canarium indicum 0.560 1. There are two primary types of woodhardwood and softwoodand both are used in different types of construction projects. Technically, specific gravity is a measure of the ratio of a woods density as compared to water. If wood were the same density as water, the specific gravity would be 1.00. However, by extrapolating the table by the trend rate, we conclude that the highest possible moisture content of wood with a specific gravity of 0.8 to be 52%. ) StZ2ZWP:-oN`\Ri\bX(IK8pn`;wWj\E^b,KgSobOC~70_UHc Using green SG, and yes, using the tropical equation. mention moisture content along with specific gravity. Thanks for the reply. 7 0 obj Betweenscientificand woodworking standards, there are at least five different ways to express specific gravity, and oftentimes sources (particularly woodworking publications) will make no attempt at identifying which standard is being referenced. The Pennsylvania State University Press. See my page on donating wood samples for more info. Page 199. The most comprehensive tables of specific gravities, both basic and at 12%, for North American woods that I know of is compiled in "Specific Gravity and Other Properties of Wood and Bark for 156 Tree Species in North America", by Patrick Miles and Brad Smith. As specific gravity is just a comparison, it can be applied across any units. Technically specific gravity is the measure of a woods density as compared to water. My question is in regards to btu values and certain species of wood. Extreme ends would be more like .1 1.4. After spending a couple of years working with industry leading builders in Austin, Jordan and his wife Veronica struck out on their own to form Smith House Co. :mhY=W~,-yZ8d>3}R->-SoR*lbYN9L
Support me directly through PatreonIf youve been helped by the Wood Database, consider saying thanks and helping to support the project. I am not asking about any of the other many Canarium species found all around the planet, just these two, please. Specific gravity, green moisture content, and weight of selected North American wood species. << d%^~\@ya? If you are trying to find BASIC specific gravity, that is another story, and a much longer explanation.
specific gravity of the material at any moisture content GMC . Temperature and purity will often have a definite effect. For thousands of years, wood has been used for construction, and for making tools, weapons, and furniture. Smith House Co. strives to build more beautiful, functional and resilient spaces which are self sustaining and harmonize with their natural surroundings. Substituting these values for the grand average MC used above, and using the specific gravities for the species from which we get the MC range values, we get: Oak-Hickorygreenlow = 620 * (1 + 0.56) = 967 kilograms/m3 , or 60 pounds/ft3, Oak-Hickorygreenhigh = 610 * (1 + 0.85) = 1129 kilograms/m3 , or 70 pounds/ft3.
WzfiCJ,mEGQ*+Z)0 +4A .6*Bt:y^Zv4>Jhfg4njwM]qfY)YH"?\E*I R Table 4-1 of the 2010 Wood Handbook2 gives the heartwood and sapwood moisture contents of 40 North American hardwoods, and 28 North American softwoods. So a correct statement in the original article should have been that oaks and hickories average between 60 and 70 pounds per cubic foot green. For softwood, this is practically always true. 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. What Is Thinset? ), You can help support the site by buying one of these resources, designed and published by The Wood Database. (At least with average dried weight, the moisture content is generally assumed to be at 12% unless otherwise noted.). Fa#'p{~T!XfX'DXYIEGF-XJ NAu;=|EBsdg]AQ4.Ac!bnx7^[,ZIlI\}%P~3P!=D(R-s,T+^-m` L.=SWg[k9#u:;TwFbvmqrkH|I;7~'$m\%Taw{]Mt5w tqDhN|4.0+=X={4H!hEEUg(UDEsPuPuMDPm4F}5D3ct:TAW @)}. The most technically correct way to calculate weight of wood gets somewhat tricky, because the specific gravity of woods changes with moisture content once the moisture content goes below 30%.
circumstances into account and the presented results should not be considered as the sole basis for making important decisions. Some other standards set pure water at 60F as sg = 1 so it is more correct to state the base used. See this article for more info: https://www.wood-database.com/wood-articles/wood-and-moisture/. gravity of species in their green state, which is called basic specific gravity By entering your email, you consent to receive communicationsfromPennStateExtension. We see in this example that an increase in moisture content results in the increased weight of green wood. Density is a function of an objects volume and mass. If a species of wood has a higher basic specific gravity than another, wouldnt that species also have a higher btu value than a species with a lower basic SG? Hematite specific gravity 5.26 is only rated 5.5 6.5 mohs. The researcher must be able to calculate the density of the wood at the moisture content of interest. Canarium indicum (aka Red Canarium) Thanks. Since the volume of wood changes based on moisture content, attached the calculation sheet. What can be said about wood that is always used underwater, which species is the best, what is their SG, moisture level calculations, and specific gravity, etc? This website is designed to be informational and educational only. Recall that specific gravity is density in grams per cubic centimeter (g/cm3); since the denominator of the specific density is one cubic centimeter, and assuming we want to calculate the weight of a cubic meter, we simply have to multiply 0.59 * 1000 to get 590 kilograms as the mdry for Equation 2. So another way of thinking about this is that the density of green wood (that above 30%) is different (less) than the density of the wood as stated in most references, which are usually given as specific gravity at 12% moisture content, for the purposes of aiding those who work with wood. Its basic density is 0.80. (The basic specific gravity is identified by that at "green" moisture content in the tables, as opposed to the specific gravities listed at 12% moisture content.) Technically what you say is true for minerals. Thanks, Density at 12% moisture content; and about 1.3m3 of seasoned sawn timber per tonne: aulacocarpa 800kg/m. No, it would reach what is known as equilibrium moisture content, which is, as you guessed, dependent on relative humidity. But denser woods are also more likely to split if a large fastener is driven into them. Why do we need this?
Submerged wood reaches whats called its fiber saturation point (FSP) which varies a bit for each wood species. The presented calculator extracts percent volumetric shrinkage values from Unfortunately, the tables only go up to a specific gravity of 0.7, where the highest possible moisture content is listed as 72%. Hello Mr. Eric, Thanks for the Video. Recall that mdry is the mass of dry wood and MC is the moisture content at which we wish to estimate the weight. The developers worked hard to ensure the accuracy and correctness of the data presented in this website. `R6t m Now we have all we need. The moisture content calculation is simply a comparison of the mass of a sample of wood at any given moisture to its mass when "oven-dry", or when all the water has been removed from the sample. /ColorSpace /DeviceGray The equation used for calculations is quite simple: So, to use a simple example, if a sample block of wood weighs 50 grams at original weighing, and 40 grams after being dried to 0% moisture content, then the moisture content of the original sample was (50-40)/40, or 25%. MT Copeland offers video-based online classes that give you a foundation in construction fundamentals with real-world applications. Table 4-1 list 12 species of oaks and hickories, and they average. Easiest way is to just take density and divide by 1000, so SG = .442. Those materials have a specific gravity more than 1. You already have the wood density, so that is what I would use. For the species in the table, the hardwood heartwood averages 81% moisture content, while the hardwood sapwood averaged 83%; the softwood heartwood, however, averages only 60%, while the softwood sapwood averaged 152%! The basic difference between the two classifications is not in their actual hardness. * Green heartwood and sapwood moisture content data taken from Table 4-1, 2010 Edition of the Wood Handbook. , and for making tools, weapons, and furniture. Hk$(L`rLW`Zdo 9L*,_>LNs jmGqjw-qU}+Iz:JWw77vMoo{;/>Y}~?O_|net6>{?wW~2eV-M %:0n`o+ LEARN HOW TO SLOW THE SPREAD OF THE INVASIVE SPOTTED LANTERNFLY.