Wood – the burrs, spalting and other decorative features in wooden bowls

The wood I use for the work I sell comes from sustainable sources – naturally fallen trees, site clearance, recycled timber and hardwood offcuts. It’s all material that would go to waste if not used. I use the most interesting and beautiful English hardwood varieties I can find. Seeing what the grain and figure of the wood look like in the finished bowl or other item is one of the things I enjoy most about woodturning. The wood often has features that can be highly decorative.


Burr figure in oak
Burr figure in oak

Timber with burrs or spalting can make specially attractive pieces.  Burrs are the twiggy, lumpy growths sometimes found on the side of a tree.  Burred wood has very small, tightly packed knots and distorted grain. It gives a very striking and complex figure, very often with small cracks and fissures. There are usually examples of burred (and spalted) timber on my bowls page.

Spalted wood

Spalt zones in sycamore
Spalted sycamore

Spalted timber can have spectacular patterns, with dark lines and areas of different colour. These are made by the harmless fungi that once grew in the log. Different kinds of spalting give different effects. There may be single crisp black lines, or pairs of closely-spaced parallel lines wandering over the wood. Sometimes there is a cloudy variation in colour without sharp boundaries. Often the colours are clearly defined and separate. Spalt colours may include chocolate brown, white, green, black, orange, red, yellow, pink and blue.

Left unchecked, spalting progresses until the wood  becomes soft, porous and weak. Toadstools may sprout from the log. Eventually, the log would disappear into the forest floor. But if caught at the right time, the wood retains much of its strength. The finished item is stable and durable, though spalted wood is never as hard and strong as unspalted. It would not be suitable for load bearing applications.

The rate of progress of the fungus can vary within a piece, so that sometimes a bowl may have small spots where the effect is more advanced. These may give the wood an uneven surface, where the softer spots cut back more rapidly as the bowl is sanded smooth. These spots may respond differently to the oil finish I use, leaving them with less of a sheen. I sometimes use a stabiliser such as penetrating cyanoacrylate glue to harden these spots, but usually leave them as they are. As with all these features, they are part of the story of the wood. Sometimes the fungus itself can be seen penetrating any small cracks or fissures in the wood.  

Although spalting is a natural process, it can be encouraged by leaving the timber in suitable conditions. I left some beech logs in the woods undisturbed for a couple of years, with great results. All it needed was time, and luck, because not all fungal growth produces good quality spalted wood.

There can be great variation even within one piece of turning timber. So there can be considerable differences in appearance between two similar items made from that piece. One part of the log might have small bark inclusions, where the wood has grown over part of the bark, perhaps following damage years previously. Another part might have meandering tracks or holes,  the evidence of past insect attack. There are sometimes cracks caused by stresses in the standing tree or by shrinkage during drying. There may be coloured streaks in the wood caused by buried metal. A nail hammered into a live tree will slowly be overgrown and enclosed. It will become completely hidden in the middle of the log. That doesn’t make the turning any easier! Depending on the species, the metal staining may be black or purple. Bark inclusions often have natural fissures that I sometimes fill with metal or other inlay for decorative effect.

The natural colours of some woods can be very striking, but often fade or darken with time. I see them at their best when turning unseasoned timber. At first the colours are vivid, but they often fade quickly.

Ripple and crotch figure

Sometimes the wood has ripple figure – beautiful undulating grain that catches the light. It’s as if you are looking beneath the surface. The grain looks as if folded, even though the polished surface is smooth and flat. The waves in the grain are real, and I see them clearly when the log is split. Sometimes you may see the ripples as small corrugations on the bark of the living tree. Ripple figure forms where branches join, but occasionally it extends through much of the trunk. It forms where the wood grows under greater than normal compression.

crotch figure in oak
Crotch figure in oak bowl rough-out

Crotch figure forms where the trunk divides, or large branches join. Depending how I cut the log, there may be a single feathery line going across the bowl, or a large area might be affected. Crotch figure can be spectacular and, like ripple, can shimmer as the light catches it. The example above appeared when I started to rough out a bowl from a block of oak. The photo shows the figure on an unfinished surface. This piece also had a hole where a dead branch had rotted away. It had been partly overgrown by new wood.


All trees have heartwood in the centre of the trunk and sapwood under the bark.  Often the two look similar, but in some species there is a colour contrast. Usually the heartwood is dark and the sapwood pale.  Laburnum, yew and whitebeam are species with a strong contrast. Some species such as ash may have dark streaks in the heartwood.

Bog timber is found in some parts of the country. This is wood that has lain submerged in a peat bog. The acidic peat preserves the wood and blackens it. Though often somewhat unstable and degraded in strength, the better pieces can be turned into very attractive and unusual work. Bog oak from the ancient oak forests is well known, but other species are found too. Radiocarbon dating proves that the wood is thousands of years old.

All these natural features can add interest. They enhance the beauty of the wood and make it very suitable for decorative pieces. Such timber is usually fine for fruit bowls, but bowls that are heavily spalted or burred or have bark inclusions are not recommended for moist food such as salad.

Sometimes, I add colour, carving or other decoration to the finished item. Although I make many of my pieces from wood that is spectacular in its own right, others are more subtle. Good turning does not depend on colourful timber. Satisfying though it is to use highly decorative materials, I also enjoy using timbers such as holly or hornbeam. They are often pale in colour and without prominent grain. Without distraction of figure and grain, such pieces let the turned shape of the piece dominate. I like to think they are some of my best work.

Tree species

I use many species of hardwood trees, but rarely use softwoods such as pine. The classification of hard and softwood comes from botany; softwood trees are conifers, and hardwoods are mainly deciduous. Yew is technically a softwood but is physically harder than many species classified as hardwood. It turns very well and all turners like to work with it.

In temperate latitudes, trees grow most quickly in spring and early summer. That wood tends to be softer and more porous than the slower growth at other times. The annual variation makes the visible growth rings in the log. Counting them tells you the age of the tree. Slow-growing trees have their rings closer together and their timber is more valuable. In contrast, tropical species grow all year round and are much more uniform in density.

As a maker of bowls, I like timber from large trees. But small ones have their uses too. I make wooden mushrooms from small branches. Some shrubs have fine, compact grain and turn and finish well. Others such as elder have a tube of soft pith in the centre that limits their use.

Structure of wood

All wood is porous. But some species have much more visible pores than others. Some oak varieties have large pores like pin pricks, big enough to see through in a thin section. They show in the finished item, unless filled. In past times, cabinet makers went to some pains to fill the pores. They wanted a glass-smooth finish. Now, many woodworkers are happy to show the natural appearance of the wood. But the pores do affect the function of a bowl. An oak salad bowl, with its exposed porous end grain, might leak oil.

Some wood species have characteristic ‘rays’. These are radial sheets of cells that play a part in sap distribution. The rays are visible as small flecks or as wider patches or streaks. Their appearance depends on the angle at which they intersect the surface of the wood. This means that the same piece of wood can have markedly different appearance, depending on how it is cut. Quarter-sawn oak has its prominent rays parallel to the cut. It looks quite different from plain-sawn oak cut across them. The example in the photo was revealed when I was turning a bowl from a block of unseasoned oak.

ray structure in oak
Ray structure in oak

Wood from a plane tree, when cut in the right direction, is known as lacewood. That’s because I ts complicated ray structure resembles lace. Turned work does not show these rays so clearly as cabinet work, because the surface is only parallel to them at one point on the curve. But they may form a band on the side or rim of a bowl.

I can saw a log in different ways. If I cut it into parallel slices, the growth rings align differently in each plank. The first and last slices, closest to the surface of the log, have the rings more or less parallel to the faces of the plank. These ‘plain sawn’ planks, although attractive, are more likely to warp than quarter sawn timber.

I saw some planks directly through the middle of the log. These are ‘quarter sawn’. The growth rings are then more or less parallel with the edges of the plank, not its face. This wood is the most stable, and preferred for furniture making. Plain sawn and quarter sawn wood look different in turnings because the angle at which you see the growth rings greatly affects the figure. Often a bowl contains both, the plain part usually in the bottom of the bowl, the ‘quarter’ at the rim.

Wood as a medium for craft and art

Wood is a marvelous medium for craft work and art. Watch how someone will pick up a well-made piece. They pass their hands over it almost as if absorbing something from it. And that is just what they are doing – they are taking in the natural qualities of this wonderful material. The polished wood can evoke the calm of the forest, the imposing presence of a full-grown tree, the durability of old oak beams and the delicacy of fine furniture.

Handling a piece of timber puts you in touch with its history. In each piece, you can see the annual growth rings that tell its age. Over the years, events in the life of the tree leave their mark. In good growing seasons the rings will be wider. Burr formation may date back to an injury to the tree trunk. A branch broken in a storm long ago and enclosed by later growth leaves dead knots and disturbed grain in the wood. Insects may attack the sapwood, leaving holes and tunnels under the bark.

A nail driven into the trunk years ago may leave no visible trace on the surface of the log. But there may be tell-tale staining in the wood itself, a warning to the craftsman that tool edges are at risk. Spalting shows that the tree suffered from fungal attack. This can happen while it is standing. It can also develop while the log lies on the damp ground before use. 

The right timber for the job

The craftsperson, particularly in past times, had a great knowledge of wood. He or she knew the properties of different species of timber. They selected the right wood for the function of the item. They would pick oak for its strength and durability when building a house. Elm for its resistance to splitting when making cart wheel hubs. Sycamore for its fine grain when making kitchen ware. Beech for its workability and strength for everyday furniture. And they chose ash for its toughness when making tool handles. They preferred straight grained timber for its ease of working. They rejected knots and bark inclusions because they weaken the wood. Craftsmen considered spalted wood to be waste. Burr wood was not strong enough for furniture. But it was valued for decorative veneers to be overlain on stronger material. 

Sometimes appearance is as important as function. If conditions of use are not too onerous, the maker chooses material for its beauty. People value bowls with swirling grain, spalting, knots and burrs, bark inclusions and even insect damage.  

The demand for cheapness shows in the difference between mass-produced wooden bowls and those that I make. At the factory, timber must work easily without needing individual attention to each piece. The results are plain, uniform and bland.

Artists may sometimes also prefer plain timber, but for different reasons. They want people to appreciate the shape of their work undistracted by the material. A wood carver may need fine, straight grain to enable fine detailing. A sculptor may want to make large pieces, eliminating the small trees that turners can use.  But sometimes artists will pick wood with more character. They may incorporate its natural features in the design. The finished work may have a silky-smooth finish. Or it may have a surface with texture, whether natural or applied. They may want the contrast of rough and smooth in one piece. Few materials are as versatile as wood.