A few facts about wood: The Intro.

    Understanding even a tiny bit about wood can make you a much better woodworker. So lets start with some basic safety advice:

    Working with any timber is a potential health hazard:

    • Ignoring all chemicals, even if you have a freshly cut piece of timber from an organically grown and recently harvested log, you don't want to be breathing in sawdust! It's bad for you.
    • Some species of wood are naturally toxic, even if it's just saw dust. Others are far worse if you burn them (even if they don't have any chemicals) by producing more effective toxins, carbon monoxide, and other hazards.
    • Synthetic/engineered woods and treated timbers have multiple additional risks to natural timbers. Never burn them, and be sure to wear safety equipment like dust masks when working with them.

    The lumber you will likely use in wood working comes in three main categories:

    1. Natural Timbers
    2. Treated timbers
    3. Engineered timbers.

    Natural Timber:

    Describes any timber simply milled (cut) from a log or branch. However, before we go too far, let's look at some facts about natural wood.

    • Wood is made of fibres, and these fibres aren't always parallel to your boards. If they go diagonally through your wood, the direction in which you cut, plane, and even sand your wood, and your chosen methods of joinery used can make a difference to how cleanly, smoothly, or strongly your project ends up.
    • Wood varies a lot from one species to another, even individual trees within the same species, and these differences may include a mix of strength, flexibility, hardness, water resistance, prevalence, availability, or even the ability to transmit sound!
    • Wood varies within even a single piece of timber!
      • Since wood is grown, rather than manufactured like steel or plastic, it's far from consistent throughout. If you've ever seen a cut end of a log, you'll see alternating concentric light and dark rings. Small circles of the inner wood are inside ever-growing rings until you reach the bark (if it's still attached). Each light coloured ring is a fast-growth period, (spring and summer) while the dark lines indicate a slower growth period (usually autumn and winter). So knowing this fact, you can count the number of rings and figure out how old the tree was when it was cut down.
      • Both the light wood rings, and the dark wood rings have differing properties. The light coloured stuff is less dense, so it is softer and more flexible, the darker stuff is harder and more stiff. Interwoven layers of hard and soft wood makes it quite strong while relatively flexible.
      • Some species of trees not only have the rings, but literally push all the usable nutrients to/through the outer wood (also called the "sap wood") to help grow and maintain leaves, while dumping any unusable materials found in the soil into the core of the trunk (called "heart wood") which is used as a vague skeleton (and dumping ground) for the tree itself. Trees like this have hard, dense, compression resistant heartwood, while the outer sapwood is softer, more flexible, and "stretchy". One of the most famous tree for this is the "Yew" tree. It was harvested almost to extinction before firearms were commonplace because the wood made fantastic archery bows. To this day, you'll find centuries-old Yew trees located on historical sites like abbeys, churches, and grave yards because these areas were defended or merely occupied by archers, so growing these trees nearby made sense.

     

    Hard wood versus soft wood

    Different species of trees produce different types of wood. While there is a lot of grey area between the two extremes, wood is usually grouped into two different categories. Slower growing (and often deciduous) trees often have more dense wood, and are called "hard woods". Faster growing trees (often ever-green trees) have less dense wood, so they're often called "soft woods". I'm sure that's a simplification, but for now that's enough.

    • Soft Woods:
      • Benefits of soft woods:
        • Cost:
          • The most prolifically available timbers are the softwoods like the ever-available generically labelled "pine" (Although please note that there are some harder pines too). Foresters can plant trees and have them ready for harvest in anywhere between 10-30 years. This makes pine wood cheap, lighter weight (which is useful for some applications), and most importantly, relatively renewable. As such, pine and other soft woods tend to be on the cheaper end of the scale. Also, being softer, cutting softwoods is easier on your arm/motor, and blades typically last longer as it's not quite so difficult to cut. This means you can get by with cheaper, or smaller power tools, and replace your blades and router/drill bits less frequently. So it's cheaper up front, and via associated costs.
        • Easier to work with:
          • Wood working with soft woods is more forgiving, as there's a sort of "sponginess" to them. If your joints are a little tight, or even a little loose, it's not inconceivable for the wood to "bend to your will" in the right circumstances.
          • Soft woods are also useful because being less dense, they're lighter to move and work with.
          • Also I'm not certain, but pine seems to be stained a little more effectively with less staining product. In general, soft woods are very useful wherever you don't imagine they'll need to take much of a beating, or need to be particularly strong.
      • Downsides of soft woods:
        • Easily marked:
          • I suppose it comes down to a matter of application, but many softer woods are easily marked. Camphor wood, like pine and other softwoods are easily scratched, or dented by abuse, or even an accidental scratch with a finger nail. Some people like beating up new soft wood furniture to look "old" with chains to give it a "Shabby Chic" look.
        • Softer woods are also less suited for particularly heavy loads, especially when joined using weaker joints... also being soft, softwoods are eaten by termites faster as well. However, some have natural resistances which make the species less attractive to particular wood-eating critters.

    A side note:

    My university was genetically engineering Poplar trees (not "popular" as some people I know call it) to grow in even less time, but the wood was so poor they had a tendency to snap and fall down in only moderate wind. Being a public safety hazard, they were removed.

    Don't get me wrong, I like soft woods, and they're strong enough for many tasks. I have no chance of breaking a 50mm (roughly 2" in the old parlance) thick piece of pine, even if I jump on it... unless my weight is placed on a long cantilevered beam or something. My home-made work benches almost all use pine for the framework. House frames are often made of treated pine. It's not weak, it's just not as hard wearing as the harder woods.

    • Hard Woods:
      • Benefits of hard woods:
        • Hardwoods have been popular for many, many reasons. I think the main ones are:
          • They're longer lasting,
          • they can take more of a beating,
          • they are better at bearing really heavy loads. But perhaps the most important one is...
          • that hardwoods are just so darn pretty. Whether you have a walnut table with gorgeous burl patterns in them, or the deep red of Mahogany, (don't confuse that with monogamy), Jarrah, or Red Gum. Ironbark is another particularly hard, dense wood that has been used in railway sleepers, and it lasts quite some time, depending on the conditions, thickness, and application.
      • Downsides of hard woods:
        • Cost:
          • Unfortunately, many of the best hard woods have been harvested from forests in an unsustainable way. Combining this with the substantially longer time it takes to grow hard wood trees to maturity, means that "sustainable" management means "leave it alone for many decades, or even centuries", which just isn't economically viable. (But probably ecologically essential) As a result, so many species are getting very rare and extremely expensive. Go back 50 years many of today's expensive woods were cheap. This is why buying antique furniture (which is a bit unpopular at the moment, with their currently low prices) can be particularly worthwhile. Merely knowing the value of wood can indicate if buying a particular item may be a great investment. Case in point:
            • My university college was founded in 1971. At the time, wood was plentiful so it sold at a fraction of the current cost. As a result, large tracts of the college was made of (now rare) types of cedar, and each dining hall table was made "on the cheap" out of Tasmanian Oak. There are over 50 tables, and now each table has over $2500 worth of wood in them. There's literally millions of dollars worth of wood in that place. If you think the cost of copper has gone up, hard woods have to be on a similar price trajectory.
          • Hard woods need bigger/more powerful tools to cut and shape them if you do that a lot. Since I work with a lot of hard wood I only buy professional grade tools now, and replace or sharpen blades more regularly. That adds some serious expense, not just in buying, but in the ongoing maintenance and insurance too!
        • Weight:
          • Hardwoods, due to the density, also have the downside of being particularly heavy! It doesn't take much Ironbark to reach 20Kg (roughly 44 pounds in American) so it's entirely possible to hurt your back if you aren't careful. Building anything from it needs to be a relatively immobile item. I'd recommend it as a decorative exposed rafter, but it's impractical for a lot of furniture. A "rustic" 6 seat slab-style kitchen table could easily exceed 250-300Kg depending on design.
          • The density comes at another cost, and that is "not having much give" in the wood. This means hard woods are more unforgiving of mistakes. Errors in joinery are visible if they aren't perfect, and need to be fixed (or covered up) somehow.
        • Harder to find "good" hard woods.
          • A lot of stores sell huge amounts of pine and engineered wood products.. but you're not likely to find "the good stuff" in your average Bunnings, or big box store. Yes it's going to take more effort to find, but there are things you can do.. all involve some level of effort, but that's what you're here for:
            • Take the time to visit real lumber yards, talk to the people there, and develop your contacts. I managed to get some amazing "off cuts" the size of my leg, by merely being polite, talkative, and asking.
            • Alternatively, look up reclaimed timber sellers, or even your local recycled building material co-operative stores. Again, develop those contacts, get to know them, tell them what you're interested in, and give them your contact details. I've had some phone calls that go along the lines of: "Hey Ham, are you still interested in some nice deep red timber like Jarrah, Red Gum and the like?... If so, there's a guy who's dismantling a stair case, and you can have the wood if you help him to remove it". I was understaffed that week and had to work. Turns out it was nearly $30,000 of beautiful 100 year old timber, all neatly finished, with just a few holes in it. Yes, I'm bitter... but I also have no idea how I'd justify storing that much timber to Wren. It is also one of many reasons I left that job.
            • Have you tried the local classifieds? Whether it's online, or in a newspaper, sometimes people just have excess timber to get rid of. However, most wood workers know the value of good hard woods, so don't expect it to be free. :-) At the same time, don't just pay the asking price, do your research and figure out what a fair price might be. To do that, you need to know both the type of wood, the dimensions, and see (at least) a photo showing if it hasn't got any problems. A quick search online, or simply calling up "for a quote" from a real lumber yard will give you a fair idea. Heck, be honest with your favourite lumber yard, say "I'm considering getting this, is it a good deal?" They might have something better, or something similar at more reasonable cost, maybe even both.
            • Buy old furniture!
              • It may seem counter-intuitive, but sometimes complete older furniture is cheaper than the wood used to make it.
                • According to a friend in "the biz", antique stores aren't doing so well these days, so ask them if they have any damaged goods. Repairs might not be cost-effective to a store overloaded with stock in this climate. But it might be a good chance for you to learn some ways to repair a finish!
                • Or simply buy old furniture.. it may actually be cheaper than making it.
                • Or you could break down old furniture to study the design/construction and salvage the wood. You might need to strip finishes and be a bit creative to make it work.

    Treated timber products:

    Somewhere between natural timber, and engineered timber is the treated timber range. Treated timber is usually natural lumber (or ply wood, discussed below) that has been chemically treated to slow rotting and deter termites. You can see identify some treated pine products by a characteristic green-ish tinge. Some are intentionally dyed with unnatural colours to indicate that they're treated. However, it's not always easy to identify whether a piece of wood has been treated or not, especially if it has "greyed" with age.

    To make matters more confusing, not all treatments are the same. Older treated products were treated with an arsenic solution (a potent poison) which has raised concerns about the safety to use it in places like playgrounds, and vegetable patches. Newer treated products, claim to be "safer" (note that saf-er is not the same as "completely safe") because they have used a different solution, by reducing the amount of arsenic (not removing it) and combining it with copper and chrome. (aka: "CCA" treatment). Copper deters fungus, Arsenic kills borers and termites, and apparently the Chrome bonds them together somehow. CCA treatments have been standardized and come in a variety of "strengths" from "H1" to "H6" (here in Australia). H1 refers to the "Hazard level". As you might imagine, H1 is the "safest" but also has the least wood protection. "H6" lasts the longest, but also has the greatest chemical risk.

    • Benefits of treated products:
      • Greater fungus/borer/termite resistance.
      • Allows you to use woods where they might ill suited, or likely to be exposed to the elements, rot, or pests.
      • Cheaper than many hard woods.
    • Drawbacks of treated products:
      • Can leech chemicals into soil if left there. Not recommended for food-producing gardens.
      • Burning treated timber is extremely hazardous. Don't do it!
      • Breathing in treated sawdust is a potential hazard as well. Dust extraction, dust mask, and proper disposal highly recommended.
      • Unknown extent of health risk from long-term exposure.
      • It is not always obvious whether timber has been treated or not. Especially true of wooden pallets. They might use eco-friendly ways such as kiln-drying, or debarking. However, Methyl Bromide is a particularly potent poison to stop international quarantines from being breached by "stowaways". For more information, I have an article on that on this site called "Reclaiming Pallets".

    Engineered Wood-like Materials:

    While all wood must come from a tree at some point, your typical solid lumber isn't the only option around. Ply wood, particle board (a.k.a: "Chip board") and MDF (a.k.a: "Medium Density Fibreboard") are three of the most common products in this area. All of them involve some form of wood and glue, but they do it in decreasingly natural ways. The big advantage of engineered products is that you can build it to any size, dimension, and tweak them for different purposes without trying to grow the biggest tree conceivable. Most people won't be concerned about custom-made, ship-sized stuff, and just deal with the commercially available supplies. Let me outline the benefits and costs of each.

    Plywood:

    Plywood is the most natural of the big 3 engineered woods. Although that isn't saying much. You certainly won't see this wood being cut "as is" from a tree trunk. Instead, ply wood manufacturers take thin sheets of natural wood, then glue the sheets into stacks of odd numbered layers. You might be asking: "Why is it odd numbers of layers?"  The only answer I have been able to find is so that the grain on both sides goes in the same direction, giving it a more natural look. If you ask "why bother?" You see, each layer has in ply wood has the wood grain perpendicular to the layers above (and below it if it's not an end sheet). That way, the wood is strengthened and made more stable by doing so. But if you have the two sides with the grain going in perpendicular angles, the wood looks weird, it makes wood orientation yet another important thing us mere DIY'ers to forget to consider, and causes inconsistent exposure to the elements if the ply wood is left out "to weather".

    Plywood sheeting comes in thicknesses ranging from 2mm to 20mm (at least where I live). I've also seen up to 50mm in planks... usually structural treated pine, known by builders here as "LVL" or Laminated Veneer Lumber. Naturally, as the thickness increases and number of layers goes up, so does the weight, cost, and strength of the wood. Plywood also comes in various kinds. Some are hardwood, others are pure soft woods like pine. Some don't bother filling in the gaps between layers (called "voids") while others fill the gaps to make "void-less" options. Naturally, the void-less type is more expensive. Top grade ply also comes with consistent, knot-free hardwood finishes (top and bottom layers are blemish free) which might also be "marine grade" for exposure, and hardiness. Since I am an "in-lander" with no convenient coastal access, marine grade to me just means "pretty", allegedly more "resilient", and far more expensive.

    Because plywood is made in numerous locations. There isn't always a consistent system to judge the rating of a piece of plywood. So do your research, and understand the ratings used in your area. If that's not an option, have a good look at any piece before purchasing, and consider the needs of what you're trying to do.

    • Benefits of plywood:
      • Plywood is a stable, workable, and versatile material. It can also be incredibly strong.
      • Since it comes in so many varieties, there's a huge range of applications (and prices) that need to be considered. I use plywood as my engineered product of choice in most of my workshop cabinetry, and drawer construction. Mostly because it's better with liquids (particularly when finished properly) and looks more natural than the other two.
      • Of the three engineered products discussed here, plywood is the safest, and perhaps, the most forgiving. The other engineered options use more glue in their construction because the wood components aren't in sheets, but rather small chips, or even fibres. It's also more hardy as the other engineered woods do not handle exposure to water well at all.
    • Downsides of plywood:
      • Cost:
        • Plywood is more expensive than MDF and chip board.
      • Layers can separate:
        • Layers make a directionally strong product, but the layers can be separated by making cuts/drilling holes/heavy impacts on the edge.
    • Issues with cutting large pieces:
      • You need to support large sheets consistently across the surface of your larger sheets when cutting them. If you don't, you'll find that as you finish your cut, the weight of the two separating pieces may peel/rip the remaining connected layers in really rough ways. In short, to get clean cuts, support your entire sheet well.
    • Sanding can make ply look ugly. You can easily sand through the top veneer when it is particularly thin. Do your best to get your joints as close to true/square/flush/aligned as possible to reduce the need to sand.
    • Plywood can be very heavy and large sheets are cumbersome to work with.
    • The layering process means that the nominated thickness is an approximate value. A 17mm thick sheet may be as much as 2mm off in places. So keep this in mind, particularly for joints that require more precision... or installing drawers with runners. Subtle shifts in thickness can mean the runners taper toward each other or apart quite a bit over the length of the extended runners. This leads to jams or "derailing" which stops the drawers from opening or closing properly.

    Particle Board/Chip Board:

    Particle board is one of the most common components used in kitchen cabinetry (particularly the plastic coated/melamine coated stuff). It's basically a bunch of wood chips doused in glue, then squeezed under high pressure into boards of a particular dimension. If you've gotten into kitchen cabinetry, then you've probably seen the white melamine-coated variety at your local big box/hardware store. It has some interesting properties.

    • Benefits of chip board:
      • Chip board is extremely cheap.
      • The dimensions are precise (unlike most timber)
      • and is very stable (meaning it doesn't expand or contract with air bourne humidity).
      • Easy to find/easy to use:
        • It's also everywhere. You can buy it in 2.4m x 1.2 metre sheets, (usually 16mm thick) or even in pre-fabricated dimensions suitable for kitchen cabinetry, with panels already pre-drilled for adjustable shelving. It's also extremely easy to cut.
      • Melamine coated boards offer a really nice low-friction surface for workshop jigs, and whatever else you might think of.
      • Chip board is also surprisingly decent at reducing resonant frequencies of box-like speaker enclosures. Most speaker boxes are not made of natural lumber, but rather involve an engineered timber product like chipboard and have a veneer of real timber to give it a classy look.
    • Downsides of chip board:
      • Chip board is a compressed product and this makes it directionally strong, and while it can take a beating on the surface (where it was compressed) it is extremely susceptible to impacts on sides and edges.
      • Being made of chips, impacts on edges, or edge drilling, or even sawing with faster/rougher blades can tear out chips in their entirety, leaving rough edges.
      • Chip board is prone to absorbing water in the worst possible way, causing the entire board to decompress, expand, and then disintegrate. You need to keep this stuff dry. It has zero tolerance for dampness. Which is why kitchen cabinets need the plastic coating over chip board.
      • Certain types of joinery really aren't very good for chip board. If you must use edge joinery, a combination of biscuit/dowel joinery will give it a substantial improvement of strength. For the love of all things successful, pre drill and countersink your screw holes!
      • Needs the right glue!
        • Also, make sure that you use the right glue for melamine-coated boards as your standard PVA wood glue won't work very well here.

    Medium Density Fibreboard (MDF):

    MDF is another compressed wood product. Instead of using wood chips, it uses really fine sawdust and a ton of glue, compressed heavily to make sheets. MDF is a much more glue-determined as the wood particles are so much finer. You could honestly argue that it's saw-dust reinforced glue product, rather than wood... strictly speaking.

    MDF, like plywood comes in a variety of thicknesses, and often comes in large, easily available sheets.

    • Benefits of MDF:
      • Cheap
        • Like chip board, MDF is comparatively cheap to natural timber. 
      • It's incredibly easy to cut, shape & attach.
      • It's stable (again it doesn't expand and contract with atmospheric humidity).
      • It's also much less prone to warping, bowing, bending if kept relatively flat.
      • Dimensions are accurate.
      • It is another product used in building hi-fi speakers, again veneered later with something to make them look prettier.
    • Drawbacks of MDF:
      • Noticeably heavier than chip board, and even some soft woods.
      • Hates being exposed to liquid water.
      • It doesn't like being impacted on the edges.
      • Fine dust of it's construction has been known to act a lot like asbestos when freed from the board. So cutting, drilling, and sanding creates hazardous dust, and if not managed properly may expose you to respiratory problems.
      • Glues are suspected of causing cancer, burning MDF is a terrible idea.
      • The fibres are still in layers, so it's possible to peel off, or separate them when screwing edge surfaces. Pre-drill your holes!

    Wow, that was a lot of info in a page. Ok that's enough for now, I hope this has been helpful. Have fun!

    Ham.


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