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    Default You killed it - Now what??? Basic steps in timber drying for a quality product

    This is written in response to the many questions asked about what comes next after you’ve sawn a log. The topic of timber drying is important: as a professional sawmiller there are few things that make me so annoyed as seeing good trees turned into bad boards because of a lack of proper attention to detail in the steps beyond actually sourcing a tree. Sadly, it happens with great regularity and not always with just backyard/amateur/hobby operators. The reality is that regardless of how good your log was, and how pretty the timber you’ve cut from it is when it comes off saw – if you don’t do it right from start to finish all you will end up with is some very expensive firewood.

    Proper procedure here is not that hard. It does require some attention to detail. It does require some extra effort. It does take a little bit longer to do things right. And it does get better results. The production of good boards is a “whole of operation” process that must be consistently adhered to for consistent results.

    · End Sealer. If you don’t apply an end sealer to your logs you increase the likelihood of end checks and splits. End sealer will not prevent all splits from occurring in the log or boards but it will slow the process down considerably. There are a number of commercial end sealers on the market all of which are a wax emulsion type “paint on” solution, however if you don’t have access to this any paint will do – anything is better then nothing in this case. The correct time to apply end sealer for best results is within 1 hour of the tree being felled and sooner if possible. Beyond that (if logs have been end sealed already) end sealer should be applied to freshly cut ends everytime the log is crosscut in the mill yard.
    If your log(s) have not had end sealer applied when you get them and we may be talking days or weeks later, best practice is to cut the log back and apply end sealer to a freshly cut end. You are wasting your time and money applying end sealer to a badly split end of a log: it’s a preventative not a magic bullet. Minor surface checks are okay, but if the splits disappear back into the timber you won’t seal them up by slapping some paint around the exposed faces.
    When sawing if the log ends have been end sealed it will not generally be necessary to apply any more end sealer to the boards, however if you crosscut any boards then obviously you’ll have an unsealed end. Depending on the value of the lumber and cross-section size it may be necessary to seal these freshly cut board ends in the mill, however it’s not always necessary.

    How important is this? Look at it this way – if you start with a log/board that’s 3.0m /10’ long, and you lose 150mm/ 6”off each end due to end splits – you’ve now lost 10% of your log to mostly preventable degrade. Me, I work dammed hard for my timber and that 10% might be the difference between us eating and not eating, so to me it’s a lot. We also as a practice cut things long to help prevent this. Logs are sawn off at 3.2 rather then 3.0 if we wanted a 10’ board, just to allow for end splits. It is a risky practice to cut logs or green sawn timbers at the length you wish to use them at and hope that they dry without problems if you ask me.

    · Proper Milling is essential. By proper milling I mean that if you wish to stack your timber up and have it dry flat it must be reasonably flat to start with. Note that “flat” does not necessarily mean straight. We can remove a degree of bow from timber during the drying processm particularly if the timber is thinner. Bow in thicker sections (+38nn thick) is going to take a lot of weight to pull out and is best sawn out when milling. Spring is of little concern at this point: personally I don’t like stacking sprung timber but there are times when I do it. (My concern is around streamlined production as opposed to it having any effect on the drying process). Many will remove spring later (saw or jointer or handplane) rather then saw it out in the greenmill. Either is okay.

    Just as it is possible to remove bow in the drying process it is possible to make wood bow in the drying process. What you can’t have here is boards that are thick and thin, which is why this is a milling issue. If you stack boards that are thick in the middle one atop the other, then strap them down/apply weights, you will naturally get a pile of wood that is higher in the middle then it is at the ends. It will curve, and you will dry that curve into your stack of timber. What we are after here is boards that are consistent in thickness from end to end, regardless of any curvature in the timber. They don’t have to be perfect – some variation in greensawn thickness is normal - but the perfecter they are the better your end result can be. A consistent 1mm high spot in the middle of your boards will result in a 12mm rise in the middle of a pack that’s 12 rows high. Stack four packs on top of each other and that’s now a 48mm difference between the ends of the pack and the middle at the top row - and that’s just expensive firewood.

    Other than improving your sawing process overall so the problem doesn’t occur, you need to do the following: Thick Boards – pass them through a thicknesser to remove the thick spots.
    Thin boards, (or thin in patches boards) stack them so they are in the middle of each row of sawn timber, surrounded by even boards. This means they do not influence the stack above or below them.

    · Stickers. As with timber, you need your stickers to be flat. Preferably dry as well to help reduce any staining issues. There is a tendency for people to use any old bit of rubbish lying around for stickers and that’s okay, we do it too. But your rubbish needs to be flat and of even thickness; as with the sawn timber if the thickness is not consistent then you will push a bow into the timber it is supporting. It’s that simple. Ideally stickers should be KD to avoid any shrinkage differences in drying though that’s not always so important depending on the species. What you want to avoid here is having green stickers in three different species with three different shrinkage rates: they might all be the same thickness today, but as the timber dries it’s not going to stay that way long.
    Back to that word consistent again.
    The one thing about good stickers is that you will re-use them. Depending on material and drying times, they might be re-used for years. Here we would normally expect to use each timber sticker around 5 to 6 times before its broken, or becomes weak through repeated kiln cycles and overdrying. Its worth doing them right.
    If you don’t have any stickers and it’s a one off drying job – look at ripping some down out of sheets of ply. They wont hold up for as many cycles as solid wood ones will, but they will be an even thickness and it’s a quick way to get a pile of them.

    · Treatment. There are a lot of things that like to eat timber. Bugs/borers/termites/mould/fungus, all of them are problems in different species, and the best way to treat to prevent this is very application specific. Some people don’t worry about it, some do. Some use environmentally friendly reagents, some don’t care about what else dies so long as it kills whatever its supposed to. (Poisons by definition are designed to kill things). Some thought should be given to what if any treatment you intend to use and how best to apply it.

    · Stacking. Theres no great secret to stacking timber. It needs to be stacked on a flat area to keep things simple. If you’re on a dirt floor you need to think about subsidence, but other than that its irrelevant as long as its level. Then all we have to do is place our consistent thickness boards beside each other in rows, separated by our consistent thickness stickers. You need your stickers spaced evenly so that weight transfer down through the pack is direct to ground. You need the ends of boards supported which includes sticking an odd extra sticker into the pack here and there to pick up any shorts you have. You need the pack to be square when finished: square stacks can be stacked atop each other but pyramids or the leaning tower of Pisa can’t be.
    When stacking its normal to have gaps in the stack due to some boards being shorter then others or have some variation in the width of each row or “course” of planks due to different sizes being present. What you need to avoid is having these gaps situated atop each other: If gaps are above each other in course after course then air will tend to flow up through the stack rather then across or through the stack. This will lead to uneven drying of the boards.
    Sticker spacing is determined by the thickness being stacked, but its normally in the range of 450-600mm/ 18-24” apart. The thicker the material being stacked the wider your sticker spacing’s can be.

    Pretty simple right? You’d think so but it must be difficult based on a lot of what I see.

    · Storage. Storage of freshly sawn timber is most important. It must be kept on a level surface to get flat boards.

    Ideally the stacks should be supported under each vertical row of stickers to get weight transfer evenly through the stacks to the ground. Supporting bearers should be even in thickness, lest we undo all the hard work so far at the last moment. Ideally you want at least 150mm/6” between the bottom of the pack and the ground – and more if its stored outside in a yard type setting. This allows airflow to the bottom row of boards, and makes spraying under the pack for bugs easier.

    Sunlight is the enemy of freshly sawn timber. Greensawn packs should be stored in the shade or otherwise be stacked to keep the sun off them. Sun causes too rapid drying which will cause the top of the pack to curl up like a leaf, or surface check beyond recovery. In a yard type setting its common to top the sheets off with a row of dunnage boards on top m then having sheets of roofing iron to keep the sun/rain off the top of the pack. If your timber was bowed going into the stack now is the time to attend to that – weights need to be placed on the stack to hold it flat during drying and with enough weights we can bend our bowed timber back out to flat. Wet timber is of course trainable… and as it dries if you’ve done the right thing you can now train it to lie flat. If you haven’t done the right thing, this is the time when you train it to be bent: Your call.

    Stacks need to be where air can flow through them for drying, but not too much air because drying too rapidly can lead to a lot of issues with warp/cup/ twist/ surface checking. At the same time not enough air can give problems with stain/ fungal problems /moulds /mildews /rot. How fast you can safely dry is very much dependant on species, thickness, and seasonal conditions. It’s important to note that air must “flow through” the stack. Having one side open to the air and the other hard up against a wall will not allow air to flow through.

    As a general rule the denser the timber the slower it needs to dry in the initial phase from straight after sawing to 20% moisture content. That time there - when the wood is at high moisture content – is when most checking and drying faults happen, even if they don’t become visible to the naked eye until later in the process. Heavy dense timbers such as many of the eucalypts often need to be dried extremely slowly for the first several weeks, and this may require that the timber is occasionally rewetted or stored with very limited airflow.
    Conversely pines, and other “white” hardwood species where stain and discolouration from moulds are very problematic issues, will often need to be dried very rapidly at the start to remove the moisture required by the fungal organisms to survive. This may involve the need for additional airflow (fans) to remove water from the timber as fast as possible. Most softwood species can be dried very rapidly, however it can become difficult with white hardwoods due to the contradictory requirements: rapid drying to reduce stain vs slow drying to reduce checks.

    And from there we wait, remembering to check our timber occasionally and take steps to prevent any problems getting out of hand, and spraying for termites once a year…just in case. The end result should look something like this:

    IMG_20151003_172814_671.jpg


    This is a very quick overview of a very complex subject. I don’t mean to suggest that if you follow these procedures you’ll get a good board every time. Nor would I suggest that this is an exhaustive look at the steps that can go into the production of good wood: It’s not meant to be.
    What I hope you get from this is a list of the basic considerations you need to take into account when you start milling for yourself if your aim is to produce boards at least as good as those you’d buy (or how to handle your bought freshly sawn boards to get a reasonable end result from them). It is work, and some of it will seem “unproductive” – making stickers is the most boring job in the sawmill and is a never ending task (I ought to know, we’ve got a hundred thousand of the things in circulation). But its also important work if your aim is to produce a quality product.

    Anything to do with sawmills is hard work, and for those of you who do it at home often with limited tools and equipment then it can be very hard work. And to see all that hard work go into the production of firewood quality planks is heartbreaking. Even when you do it right you can still have issues with a lot of faults because that is the nature of drying wood, and some trees will want to twist or split or check regardless of what you do. Sadly sometimes thats just how it is.

    I know its a long post - and this is only scratching the surface of it. Sorry about that.

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  3. #2
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    Well written mate
    Neil
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    Brilliant post John, well done and very helpful indeed.

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    Excellent post. Dunno what your sorry for, I'd like to say THANKS.

    Cheers
    Bevan
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    Great read, no-where near milling in my woodworking journey but there was a lot of great information for future use.

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    thanks for taking the time to write this
    regards
    Nick
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    Great post.

    thanks.

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    John I have some questions if you don't mind. About stickers. I have sometimes heard that stickers should be made from the same species as is being stacked for drying. I have never done this as I have 20 species of timber and it would just be impractical. I know in certain situations using the wrong stickers can be disastrous, maybe I have just been lucky but I have used stickers made from sawn up floorboards (19mm thick) for all species from eucalypts to silky oak to jacaranda to camphor and nerver a problem. Can you comment on this please, and also on sticker thickness - I think 1" is common, but I sometimes use thinner stickers in summer to help slow the drying speed. Does that make sense? Thanks, Ken

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    Quote Originally Posted by timbertalk View Post
    John I have some questions if you don't mind. About stickers. I have sometimes heard that stickers should be made from the same species as is being stacked for drying. I have never done this as I have 20 species of timber and it would just be impractical. I know in certain situations using the wrong stickers can be disastrous, maybe I have just been lucky but I have used stickers made from sawn up floorboards (19mm thick) for all species from eucalypts to silky oak to jacaranda to camphor and nerver a problem. Can you comment on this please, and also on sticker thickness - I think 1" is common, but I sometimes use thinner stickers in summer to help slow the drying speed. Does that make sense? Thanks, Ken
    Perfect sense Ken. And the answer is... theres what I'm told I should do, some of which I take seriously and some of which I don't. it's a business and at the end of the day I know that 90% right is profitable and 100% right is often unprofitable due to the increased in cost and headache, if that makes any sense.

    I try and use "like with like" if its something particularly valuable, and if I can get "like" without too much effort. Other then that its not worth the headache IMHO.
    I try and make most of my sticks from mid coloured species of a similar shrinkage rate, give or take a couple of %. Just in case they get wet again.
    I avoid species for stickers that are particularly prone to borers, fungal issues etc etc
    I try and use only KD "white" stickers with white timbers due to staining issues (White Beech, Silver Quandong, Silver Silkwood, Northern Silver Ash, Pepperwood etc etc) White timber drives me nuts: I can do everything right and still get "salt and pepper".
    I never use stickers from wood with a high extractive content (Johnston river teak aka Merabu, Red Mahogany, tea tree, FRG etc etc) on a timber lighter then itself. I'd avoid them all together but we cut a lot of the RMY and FRG for flooring and panelling at times and if i run out of sticks thats what they come from.
    I really avoid the high shrinkage/collapse prone timbers for stickers.
    I'd like to say I only use KD stickers but theres never enough of the things so I do the occasional pack on green ones. I just keep them all one species which isnt hard because I saw in single species runs mostly, and thickness them at 22mm... then take them back to 19 later post kiln.

    Thickness depends. I'm pretty much standardised on 19mm x 1 1/4" now. I suspect 1"is mostly common because thats the size they come off the mill at in most places and I'm the only idjut who wastes time dressing them (I dont think its a waste of time obviously).
    I think 1" would be better on the whites or other stain prone timbers for increased airflow when air drying.

    It makes perfect sense to me to be changing your sticker thickness to suit the weather. I come at it from a different way: I use 19mm to increase kiln capacity and if I want it to dry faster during the air drying phase (as with the whites) I park a fan in front of it, if I want it to dry slower I hang a bit of shadecloth across the front.

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    Excellent information John and well written and all from practical experience, not from a book. Well done. I have a pack of silver ash that John cut and dried, a lifetime of woodworking experience says that that silver ash is as good as any I have had the pleasure of using, thanks to John's experience.

    Jim
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    You are just going to cut it up into tiny little pieces & then glue it back to get her again.
    Cliff.
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    Quote Originally Posted by Cliff Rogers View Post
    You are just going to cut it up into tiny little pieces & then glue it back to get her again.
    Yah, I need to figure out how to treat the white stuff in pretty patterns, so it can get white, green and black streaks or swirls or something. It's save Jim a whole lot of work if I could get three distinct colours into one board.

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    Quote Originally Posted by powderpost View Post
    Excellent information John and well written and all from practical experience, not from a book. Well done. I have a pack of silver ash that John cut and dried, a lifetime of woodworking experience says that that silver ash is as good as any I have had the pleasure of using, thanks to John's experience.

    Jim
    I have the other half of that pack of silver ash & have to agree that it is the best and "whitest" silver ash that I have seen or used.
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    Quote Originally Posted by John.G View Post
    Yah, I need to figure out how to treat the white stuff in pretty patterns, so it can get white, green and black streaks or swirls or something. It's save Jim a whole lot of work if I could get three distinct colours into one board.
    When you work that out, I'll have what he is having.
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    Quote Originally Posted by John.G View Post
    Yah, I need to figure out how to treat the white stuff in pretty patterns, so it can get white, green and black streaks or swirls or something. It's save Jim a whole lot of work if I could get three distinct colours into one board.

    Spoil sport......


    Jim
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