All About Wood: The Difference Between Brown and White Rot

All About Wood: The Difference Between Brown and White Rot 533 358 Simon O'Rourke

Welcome to our blog and vlog series ‘All About Wood’.
In this series Simon will be answering some of the questions we receive about timber. Essentially, he’ll talk about how wood behaves. That is, how it reacts to different environments, the longevity, how it cracks etc. He is often asked about these things, and rightly so! As well as being fascinating, they all impact the life of a sculpture, so it’s good to research before commissioning.
In this first part of this educational series, Simon shares more about rot, specifically the difference between brown and white rot.

Aging, not Rotting:

Simon is often asked how long a sculpture will last. And the honest answer is, that nobody knows! There is no exact science, although this blog we found gives some idea about wood durability.

A sculpture will begin to age quite early on, especially if exposed to all weather conditions. However this is very different from rotting. Aging adds different tones and highlights, increases the depth of the shadows, and overall, enhances the sculpture. If you are interested, you can read more in our blog about choosing a bronze of wooden sculpture.

Wood or Bronze Sculpture: A side-by-side photo shows the same wooden sculpture of a stylised woman's face years apart. Photo one is warm and smooth. Photo two has taken on rich, grey hues, and the weatherted wood now has the character of a real face

Side by side photos like this show that the aging process enhances the depth and beauty of a sculpture

Heartwood and Sapwood

Rot is something very different, and something Simon needs to be very aware of.

In the video above though, Simon begins with some simple tree anatomy. He first explains the difference between heart wood and sap wood:

Sapwood is the tree’s pipeline for water moving up to the leaves, and in very simple terms, is new wood. It is essentially the part of the tree that was growing most recently. As newer rings of sapwood are laid down, inner cells lose their vitality and turn to heartwood.

Heartwood is the central, supporting pillar of the tree. Although dead, it will not decay or lose strength while the outer layers are still intact. At this point the timber is actually hollow, needlelike cellulose fibers bound together by a chemical glue called lignin. And di you know that when cellulose and lignin combine to make timber, it can be as strong as steel?! For example,  a piece of timber 12″ long and 1″ by 2″ in cross section can support a weight of twenty tons! This is the part that Simon usually uses to create his sculptures.

cross section of a tree trunk showing the heartwood and sapwood

The Difference Between Brown and White Rot: White Rot

In the video above, Simon highlights where the outer edges of the cedar are already beginning to rot. In this specific case, the lignin (the part that brings the rigidity) is rotting away, leaving only the cellulose. This means the timber is beginning to get soft and fibrous and it now peels away easily. This kind of rot means the timber simply won’t take shape or hold its shape if it did – meaning Simon can’t carve a sculpture in wood affected by white rot. It would also degrade extremely quickly, which is one difference between brown and white rot.

The Difference Between Brown and White Rot: picture shows a piece of timber which has become fibrous, soft and stringy. It peels away easily. This is an example of white rot

The Difference Between Brown and White Rot: Brown Rot

The other major type of rot in trees (and something to look out for in selecting or working with timber) is a brown rot. In white rot, the lignin has rotted away. In the major difference between brown rot and white rot, in brown rot, it is the cellulose that has rotted away. This means the soft flexible fibres in the timber are gone, leaving something much more rigid. You’re left with a hard, sometimes sharp, biscuit-like, crumby texture. In fact, one of its other names is ‘Biscuit Rot’!
However, although it will take shape better than timber affected by white rot, it is still not suitable for sculpting.

an example of brown rot on a piece of timber as part os simon o'rourke's blog on the difference between brown rot and white rot

Any Questions?

We hope you’ve found this blog about basic tree anatomy and the difference between brown rot and white rot to be informative. Over the next few months we’ll be looking at lots of other aspects of how timber behaves in our ‘All About Wood’ series.
If you have questions you would like answering, reach us via our Facebook page or at www.treecarving.co.uk/contact/ and your question could feature in our series!