How to process logs for Woodturning

Countless times I have seen new Woodturner's posts on Facebook where they score a haul of small cut logs and then ask for advice on how to seal the wood for seasoning and drying. The advice given to these people is generally wrong and a complete waste of time and sealer. This is repeated on a daily basis on the various group pages so I decided I needed to address it.

The advice from other novices is normally to seal both ends of a log with Anchorseal, Emulsion Paint, PVA Glue, candle wax etc. If the log is short, you have just wasted your time and whatever sealer you have used. The wood will crack and you will lose most of what you tried to save anyway depending on how long you leave it that way. Instead, the best advice is to cut and remove the pith as soon as you can before sunlight and wind get to the wood surface. Once the Pith has been cut away from the centre of the log, then you may then seal the endgrain. Read on below.

Saving Cut Logs

After a tree surgeon has visited, if they haven't taken away the wood that is; they generally cut the tree into firewood sized logs approximately 9 or 10 inches long if asked to do so. Sometimes they do twice that, it depends on who does the job and the instructions they receive. There is absolutely no point in sealing these sizes in their current form. The wood will crack because the heartwood or pith is still intact. Heartwood and sapwood dry differently and with the piece intact the wood will pull in different directions as it dries and will form end checking cracks. This is unavoidable while the pith remains and cracks get worse as time goes by , not better. The wood will continue to crack until the tension has been fully released. You release this tension by removing the Pith from the wood.

I have created a simple drawing of the cross section of the log. The Heartwood is shown as not being a perfect circle, wood is rarely perfectly circular in shape. I am using a large diameter example here rather than a small diameter log. On large logs it is possible to get 2 or more blank slabs either side of the Pith. I have oriented the Bowls 2 different ways to show how they can be oriented as a finished product. On smaller logs only 1 small slab or blank is normally possible each side of the Pith. Please note; Blank slabs can be cut into spindle blanks should the material be unsuitable for Bowls.

Log Endgrain View with Sections

Cut Out the Pith - Always

The Pith or Heartwood should always be removed. On small logs you can cut right down through the centre of the Pith and this should be enough to relieve the tension for drying. For larger logs it is advisable to cut left and right of the pith to lessen the chances of Heartwood material moving differently and possibly cracking your bowl. The area that you cut out would then be quarter sawn material outside of the Pith and suitable for Platters due to more stable short grain.

How to Process Logs for Woodturning?

How do I process logs for Woodturning? It's really very simple. You need to process the log into blanks as soon as you can, cutting away the pith before you can seal the endgrain. The pith is the area of original growth, it has different density and will always dry differently to the rest of the log. The pith itself nearly always cracks and is always the cause of logs splitting. It is also advisable to cut away any of the bark areas as this is where insect activity will be based mostly. If the wood has woodworm, chances are that the larvae will have travelled further into the wood and are so small that you may not see their tracks. It is advisable to cut away as much of this material as possible to avoid continued woodworm presence or better yet throw it away and get something better. Why take a chance on infecting other wood or even your home!

Spindle Blanks

Spindle blanks are easy to deal with, simply cut the sizes you require and then seal the ends. You don't even have to bandsaw straight edge, an axe cut is probably sufficient if you allow enough waste but probably not the best if you want to stack the wood on stickers. Seal the endgrain and go about an inch up the sides at each end. Put the wood on stickers so that the air can get at all the surfaces and away you start the drying process.

If you do get end checks after this it probably isn't the end of the world. Some wood will crack not matter what you do and there may also have been micro cracks before you even started. I always allow a little bit of waste for my pieces so I can cut the drying checks away and I always cut the ends of new green spindle blanks with a chop saw to make sure there are no end checks before sealing them. Mostly, I aim to get 4 individual pieces from any single spindle blank length I cut. I allow a specific measurement and if an end cracks I will just add that cracked bit to the firewood pile.

Bowl Blanks

Bowl blanks are a little more complicated. If the log was exposed for a while it is advisable to cut the endgrain again exposing fresh wood without cracks. Depending on how long the end grain was exposed you could end up cutting up to 4 inches from either side of the hardwood log. You must keep cutting until all the cracks are gone. Cracks don't heal or get smaller as the wood dries, they get worse. If you want to make Bowl blanks out of small logs you should get wood to the rough turned bowl stage as soon as you can and then seal the outside edge of the endgrain with PVA Glue. You may then use whatever drying method suits you. If you leave the log as is, you will get radiating cracks going into the bowl.

Bowl Formula for Logs?

Is there a formula for figuring out a Bowl size from a log? I don't have a set formula as such but I have a basic rule of thumb; not always perfect and depends mainly on the size of the log and direction of initial Pith cracks. Cut a fresh end to the log until all large cracks are gone, there will always be a small crack at the Pith (initial crack). Orient the log to give you the best sized bowl parallel to any pith cracks and draw a line (A). Rotate this line vertically. Measure this line and then measure along the log to give you the best possible diameter for the size of log similar to the size of the line on the end and add a little bit (B). A-B will be roughly the same but adding a little bit extra along the log allows for errors or if there is a defect you can move the bowl slightly. You will be making it smaller on the bandsaw and smaller again when you true this up on the Lathe so don't worry about accuracy at this point. You will always learn something new when you cut Bowls so don't worry if you make a mistake. You learn from mistakes. Every log you cut will be different and you will figure out your own techniques over time.

Short term Storage of Logs

There will be times that you can't get to the wood to process it on the day or maybe a few days, what do you do then? A short term solution is to wrap the logs in a decent Tarpaulin. Wrap in such a way that all surfaces are completely covered by one or more Tarps and secure against wind. I would not leave this for more than one night if the logs are fresh cut as a Tarp is not a hermetic seal. If you start cutting but can't finish, put the cut sections into black or clear plastic bin bags and fold the bag over allowing no air in. Each day, turn the bag inside out so the wood doesn't develop mildew and put the log back inside the dry bag surface. This will do for a week or so. Bowl blanks should be processed within this time and spindle blanks can go a bit longer. The bigger the Bowl Blank size the sooner you should process it into a Bowl and seal the external end grain. Best advice is always to process as soon as the wood is cut so you don't lose anything.

Best Way to Season Hardwood

The best way to season Hardwood is to cut the trunk in long lengths and put it on 3 or more stickers to keep it off the ground. Wood sitting on soil is going to rot so keep it elevated. You don't have to cover the wood, just leave it exposed for 6 months up to 12 months but you should keep an eye on it so it doesn't go too far. The levels of Fungi on the endgrain should tell you how much Spalt is likely developing. This seasoning method will hopefully allow the wood to gain some colour due to existing fungi while losing some water and weight. As the wood loses water it starts to relax and tensions are released and in some other areas are increased. If you cut a fresh tree and turn a bowl straight away, the wood will move an awful lot and you will end up with a very misshapen dry shape. By letting the wood lose some water over the 6 - 12 months or so it will move far less after the 1st Turning. If you can, source a trunk about 6 feet rather than small logs. You then don't have to worry about a poor yield. Some of the more experienced Woodturners around the world will leave a tree this way for about a year or more before deciding on when to cut. Their experience should tell you what method is right.

Why do People advise Sealing Small Logs

Most people are not experts at processing wood and many people just parrot what they hear online. That's why the same bad advice keeps coming up again and again. I will say it once again. Sealing logs is a waste of time and effort, don't do it! There's no point in sealing large trunks either, the wood will crack no matter what you do as the tension moves in the wood. You will be cutting back up to 4 inches anyway so why waste the sealer?

Below is one of my earliest attempts at seasoning wood. I sealed the logs after this and wrapped the unit on all four sides and the top with black weed barrier to stop the sunlight but allow airflow. Why did I do it like this? Because someone told me that this is the way to season wood. It isn't. It isn't even a great way to prepare this wood to be firewood. I know far better these days. Again, remove the Pith and the Bark and then you can seal the end grain with glue or Anchorseal or any of the ones I mentioned above. Wood should then be stored like I have done in the last picture below.

One of my Earliest Drying Methods

Drying Spindle Blanks

You can create a drying area for Spindle Blanks quite easily for very little cost. Racks made up of rough sawn 2 x 1.5'' are quite sufficient once the weight is supported at midpoints. Below is a small wooden shed I lined with 25mm Xtratherm Insulation to control temperature. There are air vents about allowing air to free flow taking moisture away. The shelves are narrow to allow the glue ends of the wood to dry without getting stuck to the racks. 3 months in this shed with a fan assisting during the day before the wood moves on to my secondary drying location.

Spindle Blank Drying Store

Drying Bowl Blanks

There are different requirements for drying Bowls and a variety of different methods which I won't go into in this post. That probably deserves a Post on its own. My own preference right now is the old paper bag method which is slower but has better results than Kiln drying.

Conclusion

There are loads of different methods for cutting wood logs and storing for drying. What I have outlined here is correct because I have tried and tested this myself. Take everything you hear on Facebook forums with a pinch of salt as people can be eager to parrot other people's opinions to make themselves feel important. Try and get a second opinion before believing what you read and hear. Go and get a second opinion on what I have written here by all means, I won't be insulted at all.

Thanks for reading, I hope it was helpful. Post comments below if you wish. David

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