Guide for buying logs:
Things to look out for with all species:
When buying logs (or indeed deciding what goes into the firewood pile or what you are going to mill, if you don't buy your logs) there are criteria that apply to all species. These are some (though it's not an exhaustive list!):
* Ring shake: This is where you find cracks that run along the growth rings of the tree. This is the most serious form of shake, and seriously ring shaken trees are not worth milling due to fractured boards. This is what ring shake looks like:
I've found it to be most prevalent in Sweet Chestnut - I've looked at many SC logs and only milled one.
* Star shake: Not as serious as ring shake, but severely shaken trees can still be a lost cause. Seems to be worst (in my experience) in oak up here. I wouldn't automatically disregard a star shaken log, but I'd look carefully at both ends. If you can't easily see the top end of a log, look at any larger branch stubs as the shake will still be visible through the branch stubs if it is present.
* Twist: Very few trees grow completely straight. It's the degree of twist that causes the issue. The best way to judge twist is to follow the pattern of the bark. Severely twisted trees tend to come from sites that are exposed or subject to other stresses. As such (for this moment ignoring the fact that the twist will result in boards that will twist the moment they are cut), trees like this should be avoided.
* Off centre heart: If you haven't seen the tree standing, you can still get a very good idea of how it grew by the position of the heart. In an ideal world, you would only mill logs with a dead centre heart, as these trees will yield boards that are most stable. A severely miscentred heart will mean huge tension in the log and result in boards that move a huge amount both on the mill and in drying. This is accentuated with softwoods - you won't believe the movement in milling larch with off centre hearts.
* Rot: Don't automatically disregard logs with rot. It might not extend as far as you think, and in some species (like elm) it's thought that rot can cause more colourful figure further up the tree. That said, on commonly available, lower value timber, firewood a half rotted log as it's not worth the effort.
* Metal: Metal is sometimes obvious, usually not. Look for usual lines across the butt (this often means fence wire), look at the position the tree grew in and look at the butt for discolouration (blue stain from metal is only really apparent in oak, but other species can give metal away sometimes). Accept that garden trees nearly always have metal in them, pray it's not too severe and don't bother with a metal detector as they really aren't that good.
* Branching: The number of acceptable branches on a log depends on your customers. If you are selling quartersawn oak, the number of acceptable branches is zero, or as close as is damn it. Garden furniture is the other end of the scale. Sometimes branching results in stunning figure - the difficulty comes later in getting it to dry flat and machining it. Very branchy logs at my yard usually end up as mantle pieces.
* Amount of time felled: For some species, a tree that has been down for a couple of years is better (oak for instance). For others (sycamore and pine mainly), it can be disastrous. Sycamore is very prone to grey staining and will grey within a couple of months of being felled, even if felled in winter. Pine goes blue. Get the right tree at the right time of year, and make sure you don't sit on it for too long if you can. Spruce is another one - dries fairly quickly in the round and becomes very hard to cut flat once part dried.
That's about all that springs to mind at the moment - do add to it!