# burl vs spalted



## hughbie (Jun 23, 2007)

ok, i know this question is pretty basic......but ya gotta ask sometime.

what's the difference between a 'burl' and a 'spalted' in pieces of wood?

i really curious and know that you guys are great for helping us newbies.

thanx in advance[:I]


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## penhead (Jun 23, 2007)

http://hobbithouseinc.com/personal/woodpics/_figure.htm#BURL

BURL

A burl is a wartlike, deformed growth on the trunk or root and sometimes even the branches of a tree, caused by (1) an injury to, or (2) and infection in, the tree just under the bark, or (3) the existance of an unformed bud which has all the genetic material necessary to grow a full branch, or even a whole tree, but which for some reason did not grow properly. In any case, the result is that the tree cells divide and grow excessively and unevenly in a process somewhat analogous to cancer cells in a mammal. Burls are sometimes called tumors on wood, although I'm not aware of their ever being fatal. Trees with burls continue to grow otherwise normally. 

Continued growth follows the contour of the original deformity, producing all manner of twists, swirls and knots in the wood fiber. Usually, this results in wood that has a spectacular pattern that can be used to great effect in woodworking, and sometimes it is also accompanied by the creation in the burl of dormant buds which create "eyes" that make the burl even more spectacular when worked. 

Burl wood is usually darker than the rest of the tree and in some cases (Paela comes to mind) may be a significantly different color altogether. Because of the diverse grain direction, burl wood cannot be relied on for strength, but that's of little consequence since burls are prized for beauty, not strength. 

Burl wood can be difficult to dry without cracking. Sometimes there are bark inclusions in burls, and also sometimes gum pockets, either of which can cause surface defects when the burl is worked. In some species of wood, gum pockets are common in any burl found on the tree. 

Burls come in all sizes and shapes from golf-ball and smaller to hundreds of pounds of massive growth on the side of a large tree. Burls as large as 4 feet by 8 feet have been reported as have trees with hundreds of small burls. On really large trees, such as the redwood, burls commonly exist that are large enough to be used to create veneer. Burl veneer frequently does not stay flat after cutting and has to be moistened and clampled flat before and/or during application. 

"Cat's Paw" and "cluster burl" are a couple of commonly identifed types of burl figure. Cat's paw is frequently found in cherry and cluster burls are found in a number of species. Most often, burls have no sub-designation and occur in a large number of species. Common burl species include redwood, oak, ash, maple, madrone, elm and walnut. Some exotics with very popular burls are mappa (poplar burl), thuya and imbuya, and there are MANY more. 


http://hobbithouseinc.com/personal/woodpics/_figure.htm#SPALTING



SPALTING

Spalting is a dark vein caused by a pattern of bacterial rot in dead wood that once stabalized often looks like a black ink line of varying thickness and great irregularity drawn through the wood. Spalting can be encouraged by keeping a dead tree moist. Spalting is a form of decay and if spalted wood isn't stabilized at the right time, it will just rot. I need to do more research on this, but at present, my impression is that spalting is something that mostly happens only in softer woods. Wood that is really heavily spalted and still completely solid is rare, since advanced spalting is generally accompanied by enough decay to soften at least some areas of the wood.


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## hughbie (Jun 23, 2007)

thanx john........i appreciate the trouble you went though....

that's why i love this forum...........an unlimited amount of info...just waiting to be tapped.


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## Rifleman1776 (Jun 23, 2007)

John's explanation is great. But he did leave out one detail about spalting. Depending on the fungus starting the decay process and the type of wood, you can often see colors other than black. Blue, green and even red are often noted. If caught at the right time, these can produce spectacular results in a finished item.


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## Dario (Jun 23, 2007)

Burl and spalting also are not exclusive...you can have both on a piece of wood [][]


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## galoot_loves_tools (Jun 23, 2007)

> _Originally posted by penhead_
> 
> http://hobbithouseinc.com/personal/woodpics/_figure.htm#SPALTING
> 
> ...



The black streaks and veins in spalted wood have a high concentration of bacterial or fungal spores. This is not good to breath, which is why one should use a high grade of respiratory protection when turning the stuff.


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## MesquiteMan (Jun 23, 2007)

This is something really fascinating about the black lines in spalted wood.



> So, what makes those fine lines?  The White Rot fungi groups do that.  Those are called "zone lines" and are caused by incompatible colonies of White Rot fungi coming together and, I guess, not liking the togetherness. Hey, it's not just us humans that are like that! Those zone lines are laid down by each colony as a barrier to surrounding colonies. The slightly different coloration on either side of those zone lines are the results of those fungi colonies moving through the wood. White rot attacks the cellulose, lignin (although not actually "eating" it), and other chemicals in the wood giving the wood an off-white appearance.



Source: http://www.hiltonhandcraft.com/Articles/Spalting_a_Fungus_Amongus.asp


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## pilot1022 (Jun 25, 2007)

Here are some examples of Burl and Spalted wood.




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