What Is Spalting?

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Spalting is a phenomenon that occurs in wood which is not always predictable. It occurs when a fungus infects wood and causes partial rotting of the wood. Spalted wood is a high-value variety of wood but you also have to have to keep in mind that it compromises the mechanical strength of the wood.

Spalting occurs when fungi infect the wood, taking nutrients from it creating dark patches and lines as the wood dries. Spalting requires particular conditions for it to take place. Woodworkers always look for spalted wood. Varieties like spalted maple are much sought after in the world of woodworking. They also come at a considerably higher price than regular wood.

Fine line spalting in Mango wood. This spalted mango was used to construct a Romero Creations TinyTenor ukulele.
Image Credit: Melensdad via Creative Commons

Spalting needs particular conditions for the fungus to grow. Also, the timber should be under stress which explains why spalting occurs mostly in dead trees. The wood should be located in moist conditions with adequate exposure to nitrogen and oxygen. All this should take place in the presence of natural sugars.

So, you can understand why it is not easy for spalting to occur. Spalting can only take place when these ideal conditions exist. There can also be a color change where you get streaks of red, brown, and black.

Spalting tends to occur with light-colored woods like maple, beech, and sycamore. It can attack both the heartwood and sapwood of these trees. We can say that spalting happens after the fungi exhaust themselves.

It leaves marks behind in various colors and hues, adding to the visual appeal of the wood. The appearance can be further enhanced if we apply an adequate finish to the wood and polish it adequately.

Types of Spalting

Three major types of spalting occur based on the type of designs and colors that form. Accordingly, we get pigmentation, white rot, and zone lines.

A piece of spalted wood can feature one or all three types of spalting. Spalting can occur in both hardwoods and softwoods but you will find white rot and zone lines in hardwoods due to the enzymatic composition in the rotting fungi.

You will find that conifers (softwood) are more prone to brown rot, although a species of brown rot called “beefsteak” fungus occurs in hardwood trees as well.

Let us take a closer look at the different types of spalting:


Inside the wood the fungi release pigments. These pigments can occur at the cellular level of the trees. For example, blue stain pigments restrict themselves to the hyphae of the cell walls.

This change of coloring of the cells shows up in the wood especially when we cut and polish it. You will also find white rotting fungi which appear as white patches in the wood.

White Rot

Cross section of an oak trunk decaying by white rot fungus action. Decay has progressed from right side, as it was the exposed end. Left end is freshly sawn.
Image Credit: Auró via Creative Commons

A particular variety of fungi called white rot tends to have a bleaching effect on the wood. It creates bleached patches. This occurs when fungi attack the lignin which is the component of wood that gives it color. It creates an interesting visual effect when the wood is cut and polished.

When white-rot occurs in wood it is accompanied by weight loss and reduced strength. It creates an area that woodworkers call “punky.”

Brown rot is an undesirable fungal infection. Although the fungus also causes color variation, it causes the wood to crumble and crack.

Both brown rot and white rot unchecked can destroy the wood.

Zone Lines

Zone lines are dark dotting and may have random lines of black, brown, or red. It can happen with any particular type of fungus. But it is restricted to particular areas in the wood that create lines instead of patches. Wood damage does not accompany zone lines.

Price of Spalted Wood

Spalted wood of any variety tends to be more expensive than regular wood of the same species. Among the spalted wood on the market, spalted maple tends to be among the most expensive.

The spalted wood market is very irregular. The prices can vary hugely from place to place. So, if you are looking for spalted wood it is always good to do a bit of shopping around.

You need to look at the wood grade and also the extent of spalting. Sometimes, spalted lumber can come with a great deal of damage. The damage caused due to fungus can weaken the wood and render it useless.

When you finally buy spalted wood, particularly spalted maple or beech, buy small quantities from a new source. Process it to ensure sufficient quality.

Artificial Spalting

Another interesting development over the years is that of artificial spalting. The idea of artificial spalting is to create the conditions that cause spalting in wood.

Artificial spalting is an extremely popular activity nowadays. Although it is still in its infancy, people are artificially generating different types of spalting. Experimentation is going on with the different aspects of spalting.

Factors to Consider

Textured Background of Dark and Light Striped Ambrosia Maple Woo

For example, woodworkers are trying to find out which are the best types of wood for spalting. They have concluded that hardwoods like maple are among the best choices. The reason is that it can rot without too much damage occurring.

Spalting involves the development of fungi and fungi like warm and moist conditions. Therefore, artificial spalting is usually done by holding the wood in a container that should not be completely sealed to allow the fungi to breathe. Adding a bit of soil and humus can also promote fungal growth.

One artificial spalting enthusiast even suggested that you can add cold coffee. It creates a desirable pH level and promotes fungal growth.

Choosing the Fungi

Once the wood is in the container in the presence of moisture, then the next stage is to add fungi. Greenwood generally already contains some fungi so you may not have to add a lot. However, adding fungus helps in the overall process.

For planting the fungus, you can use wood that is already spalting. You can also purchase spores. Some people chuck in a few mushrooms. So, you can be a bit innovative but you have to add fungi of some sort to promote the fungal growth.

Add the Wood

The final stage in the artificial spalting process is sometimes adding wood to the fungus. However, some enthusiasts do it the other way round and add the fungus later. The important thing is to not disturb the growth. You should keep it in a place where the wood doesn’t get disturbed.

Avoid applying fungi to the end grain as it prefers to grow towards the center of the wood.

The Waiting Period

Once you have completed all the above operations all you have to do is wait. You can check the wood after five to six weeks. If there is any progress you can check every two weeks.

The trick in creating artificial spalting is not to leave the wood too long as it can damage the wood beyond repair.

Safety Measures

While spalting wood you have to realize that you are handling fungus particularly if you use spores. The growing fungus also generates spores that can harm you if you inhale them.

Use a well-ventilated area and also wear a mask while working on your spalting project. It is not advisable to engage in spalting activities if you have a respiratory condition.


Spalting is an extremely interesting subject. The process is quite simple whether it occurs in nature or if artificially induced. However, there are many different aspects to spalting.

Even as an experienced woodworker, you may not be aware of all the facts that we have mentioned here. We hope that you now have a better insight into spalting and that you can look at this aspect of wood with a new light.

Next time you come across some spalted wood, why not do a bit of experimentation and make a fine woodworking project out of it?

Happy woodworking!