Spalting
Encyclopedia
Spalting is any form of wood
coloration caused by fungi. Although primarily found in dead trees, spalting can also occur under stressed tree conditions or even in living tree
s. Although spalting can cause weight loss and strength loss in the wood, the unique coloration and patterns of spalted wood are sought after by woodworkers.
e grow in the sapwood
parenchyma
of a tree . A visible color change can be seen if enough hyphae are concentrated in an area . These pigmentation fungi often colonize wood via the rays, but are not considered decay fungi due to their non-destructive use of easily available wood carbohydrate
s . The most common groups of pigmentation fungi are the imperfect fungi and the Ascomycetes
. Mold fungi, such as Trichoderma
spp., are not considered to be spalting fungi, as their hyphae do not colonize the wood internally.
While pigmentation fungi do not degrade the wood cell wall, this type of decay can lead to a reduction in toughness
(amount of energy absorbed before breaking), and increased permeability . Pigmentation can occur on both hardwood
and softwood
, unlike other types of spalting which are more host specific.
, which is the slightly pigmented area of a wood cell wall . Some white rotting can also be caused by an effect similar to pigmentation, in which the white hyphae of a fungus, such as Trametes versicolor
(Fr.) Pil., is so concentrated in an area that a visual effect is created .
Both strength
and weight loss occur with white rot decay, causing the 'punky' area often referred to by woodworkers. Brown rots, the 'unpleasing' type of spalting, do not degrade lignin, thus creating a crumbly, cracked surface which cannot be stabilized . Both types of rot, if left uncontrolled, will turn wood useless.
. This type of spalting does not occur due to any specific type of fungus, but is instead an interaction zone in which different fungi have erected barriers to protect their resources . They can also be caused by a single fungus delineating itself. The lines are often clumps of hard, dark mycelium
, referred to as pseudosclerotial plate formation .
Zone lines themselves do not damage the wood. However, the fungi responsible for creating them often do.
s, water, warm temperatures and oxygen .
Water:
Wood must be saturated to a 20% moisture content
or higher for fungal colonization to occur. However wood placed underwater lacks sufficient oxygen, and colonization cannot occur .
Temperature:
The majority of fungi prefer warm temperatures between 10 and 40°C , with rapid growth occurring between 20 and 32°C.
Oxygen:
Fungi do not require much oxygen, but conditions such as waterlogging
will inhibit growth .
Time:
Different fungi require different amounts of time to colonize wood. Research conducted on some common spalting fungi found that Trametes versicolor, when paired with Bjerkandera adusta
, took 8 weeks to spalt 1.5" cubes of Acer saccharum. Colonization continued to progress after this time period, but the structural integrity of the wood was compromised. The same study also found that Polyporus brumalis, when paired with Trametes versicolor, required 10 weeks to spalt the same size cubes.
(Acer spp.), birch
(Betula spp.) and beech
(Fagus spp.). However, recent research suggests that sugar maple
("Acer saccharum") and aspen
("Populus" sp.) are preferred by both white rot and pigment fungi
of the wood and its structure, and then must defend against secondary colonizers that then have the ability to colonize the substrate .
Ceratocystis spp. (Ascomycetes) contains the most common blue stain fungi . Trametes versicolor
, (Basidiomycetes) is found all over the world and is a quick and efficient white rot of hardwoods . Xylaria polymorpha
(Pers. ex Mer.) Grev. (Ascomycetes) has been known to bleach wood, but is unique in that it is one of the few fungi that will erect zone lines without any antagonism from other fungi .
. A method for improving machinability in spalted wood using methyl methacrylate
was developed in 1982 , and several white rot fungi responsible for zone line formation were identified in 1987 . Current research at Michigan Technological University
has identified specific time periods at which certain spalting fungi will interact, and how long it takes for said fungi to render the wood useless . Researchers from this university also developed a test for evaluating the machinability of spalted wood using a universal test machine.
Wood
Wood is a hard, fibrous tissue found in many trees. It has been used for hundreds of thousands of years for both fuel and as a construction material. It is an organic material, a natural composite of cellulose fibers embedded in a matrix of lignin which resists compression...
coloration caused by fungi. Although primarily found in dead trees, spalting can also occur under stressed tree conditions or even in living tree
Tree
A tree is a perennial woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or trunk with clear apical dominance. A minimum height specification at maturity is cited by some authors, varying from 3 m to...
s. Although spalting can cause weight loss and strength loss in the wood, the unique coloration and patterns of spalted wood are sought after by woodworkers.
Types
Spalting in hardwoods is divided into three main types: pigmentation, white rot and zone lines. Spalted wood may exhibit one or all of these types in varying degrees. Softwoods are susceptible to brown rot which degrades the wood too quickly to be used for woodworking.Pigmentation
Also known as sapstain, or in its most common form, bluestain, this type of spalting occurs when the darkly-pigmented fungal hyphaHypha
A hypha is a long, branching filamentous structure of a fungus, and also of unrelated Actinobacteria. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium; yeasts are unicellular fungi that do not grow as hyphae.-Structure:A hypha consists of one or...
e grow in the sapwood
Sapwood
Sapwood may refer to:* Sapwood, the part of living wood where sap flows, as distinct from the heartwood, where it doesn't* SS-6 Sapwood, the NATO reporting name for the R-7 Semyorka intercontinental ballistic missile...
parenchyma
Parenchyma
Parenchyma is a term used to describe a bulk of a substance. It is used in different ways in animals and in plants.The term is New Latin, f. Greek παρέγχυμα - parenkhuma, "visceral flesh", f. παρεγχεῖν - parenkhein, "to pour in" f. para-, "beside" + en-, "in" + khein, "to pour"...
of a tree . A visible color change can be seen if enough hyphae are concentrated in an area . These pigmentation fungi often colonize wood via the rays, but are not considered decay fungi due to their non-destructive use of easily available wood carbohydrate
Carbohydrate
A carbohydrate is an organic compound with the empirical formula ; that is, consists only of carbon, hydrogen, and oxygen, with a hydrogen:oxygen atom ratio of 2:1 . However, there are exceptions to this. One common example would be deoxyribose, a component of DNA, which has the empirical...
s . The most common groups of pigmentation fungi are the imperfect fungi and the Ascomycetes
Ascomycota
The Ascomycota are a Division/Phylum of the kingdom Fungi, and subkingdom Dikarya. Its members are commonly known as the Sac fungi. They are the largest phylum of Fungi, with over 64,000 species...
. Mold fungi, such as Trichoderma
Trichoderma
Trichoderma is a genus of fungi that is present in all soils, where they are the most prevalent culturable fungi. Many species in this genus can be characterized as opportunistic avirulent plant symbionts.-Species:...
spp., are not considered to be spalting fungi, as their hyphae do not colonize the wood internally.
While pigmentation fungi do not degrade the wood cell wall, this type of decay can lead to a reduction in toughness
Toughness
In materials science and metallurgy, toughness is the ability of a material to absorb energy and plastically deform without fracturing; Material toughness is defined as the amount of energy per volume that a material can absorb before rupturing...
(amount of energy absorbed before breaking), and increased permeability . Pigmentation can occur on both hardwood
Hardwood
Hardwood is wood from angiosperm trees . It may also be used for those trees themselves: these are usually broad-leaved; in temperate and boreal latitudes they are mostly deciduous, but in tropics and subtropics mostly evergreen.Hardwood contrasts with softwood...
and softwood
Softwood
The term softwood is used to describe wood from trees that are known as gymnosperms.Conifers are an example. It may also be used to describe trees, which tend to be evergreen, notable exceptions being bald cypress and the larches....
, unlike other types of spalting which are more host specific.
White Rot
The mottled white pockets and bleaching effect seen in spalted wood is due to white rot fungi. Primarily found on hardwoods, these fungi 'bleach' by consuming ligninLignin
Lignin or lignen is a complex chemical compound most commonly derived from wood, and an integral part of the secondary cell walls of plants and some algae. The term was introduced in 1819 by de Candolle and is derived from the Latin word lignum, meaning wood...
, which is the slightly pigmented area of a wood cell wall . Some white rotting can also be caused by an effect similar to pigmentation, in which the white hyphae of a fungus, such as Trametes versicolor
Trametes versicolor
Trametes versicolor — formerly known as Coriolus versicolor and Polyporus versicolor — is an extremely common polypore mushroom which can be found throughout the world. Versicolor means 'of several colours' and it is true that this mushroom is found in a wide variety of different colours. T...
(Fr.) Pil., is so concentrated in an area that a visual effect is created .
Both strength
Compressive strength
Compressive strength is the capacity of a material or structure to withstand axially directed pushing forces. When the limit of compressive strength is reached, materials are crushed. Concrete can be made to have high compressive strength, e.g...
and weight loss occur with white rot decay, causing the 'punky' area often referred to by woodworkers. Brown rots, the 'unpleasing' type of spalting, do not degrade lignin, thus creating a crumbly, cracked surface which cannot be stabilized . Both types of rot, if left uncontrolled, will turn wood useless.
Zone Lines
Dark dotting, winding lines and thin streaks of red, brown and black are known as zone linesIntraspecific antagonism
Intraspecific antagonism means a disharmonious or antagonistic interaction between two individuals of the same species. As such, it could be a sociological term, but was actually coined by Alan Rayner and Norman Todd working at Exeter University in the late 1970s, to characterise a particular kind...
. This type of spalting does not occur due to any specific type of fungus, but is instead an interaction zone in which different fungi have erected barriers to protect their resources . They can also be caused by a single fungus delineating itself. The lines are often clumps of hard, dark mycelium
Mycelium
thumb|right|Fungal myceliaMycelium is the vegetative part of a fungus, consisting of a mass of branching, thread-like hyphae. The mass of hyphae is sometimes called shiro, especially within the fairy ring fungi. Fungal colonies composed of mycelia are found in soil and on or within many other...
, referred to as pseudosclerotial plate formation .
Zone lines themselves do not damage the wood. However, the fungi responsible for creating them often do.
Conditions
Conditions required for spalting are the same as the conditions required for fungal growth: fixed nitrogen, micronutrientMicronutrient
Micronutrients are nutrients required by humans and other living things throughout life in small quantities to orchestrate a whole range of physiological functions, but which the organism itself cannot produce. For people, they include dietary trace minerals in amounts generally less than 100...
s, water, warm temperatures and oxygen .
Water:
Wood must be saturated to a 20% moisture content
Water content
Water content or moisture content is the quantity of water contained in a material, such as soil , rock, ceramics, fruit, or wood. Water content is used in a wide range of scientific and technical areas, and is expressed as a ratio, which can range from 0 to the value of the materials' porosity at...
or higher for fungal colonization to occur. However wood placed underwater lacks sufficient oxygen, and colonization cannot occur .
Temperature:
The majority of fungi prefer warm temperatures between 10 and 40°C , with rapid growth occurring between 20 and 32°C.
Oxygen:
Fungi do not require much oxygen, but conditions such as waterlogging
Waterlogging
Waterlogging or water logging may refer to:* Waterlogging , saturation of the soil by groundwater sufficient to prevent or hinder agriculture...
will inhibit growth .
Time:
Different fungi require different amounts of time to colonize wood. Research conducted on some common spalting fungi found that Trametes versicolor, when paired with Bjerkandera adusta
Bjerkandera adusta
Bjerkandera adusta, also "White Rot," is a plant pathogen.- External links :* *...
, took 8 weeks to spalt 1.5" cubes of Acer saccharum. Colonization continued to progress after this time period, but the structural integrity of the wood was compromised. The same study also found that Polyporus brumalis, when paired with Trametes versicolor, required 10 weeks to spalt the same size cubes.
Commonly Spalted Woods
The Ohio Department of Natural Resources found that pale hardwoods had the best ability to spalt . Some common trees in this category include mapleMaple
Acer is a genus of trees or shrubs commonly known as maple.Maples are variously classified in a family of their own, the Aceraceae, or together with the Hippocastanaceae included in the family Sapindaceae. Modern classifications, including the Angiosperm Phylogeny Group system, favour inclusion in...
(Acer spp.), birch
Birch
Birch is a tree or shrub of the genus Betula , in the family Betulaceae, closely related to the beech/oak family, Fagaceae. The Betula genus contains 30–60 known taxa...
(Betula spp.) and beech
Beech
Beech is a genus of ten species of deciduous trees in the family Fagaceae, native to temperate Europe, Asia and North America.-Habit:...
(Fagus spp.). However, recent research suggests that sugar maple
Sugar Maple
Acer saccharum is a species of maple native to the hardwood forests of northeastern North America, from Nova Scotia west to southern Ontario, and south to Georgia and Texas...
("Acer saccharum") and aspen
Aspen
Populus section Populus, of the Populus genus, includes the aspen trees and the white poplar Populus alba. The five typical aspens are all native to cold regions with cool summers, in the north of the Northern Hemisphere, extending south at high altitudes in the mountains. The White Poplar, by...
("Populus" sp.) are preferred by both white rot and pigment fungi
Common Spalting Fungi
One of the more tricky aspects to spalting is that some fungi cannot colonize wood alone; they require other fungi to have gone before them to create more favorable conditions. Fungi progress in waves of primary and secondary colonizers , where primary colonizers initially capture and control resources, change the pHPH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...
of the wood and its structure, and then must defend against secondary colonizers that then have the ability to colonize the substrate .
Ceratocystis spp. (Ascomycetes) contains the most common blue stain fungi . Trametes versicolor
Trametes versicolor
Trametes versicolor — formerly known as Coriolus versicolor and Polyporus versicolor — is an extremely common polypore mushroom which can be found throughout the world. Versicolor means 'of several colours' and it is true that this mushroom is found in a wide variety of different colours. T...
, (Basidiomycetes) is found all over the world and is a quick and efficient white rot of hardwoods . Xylaria polymorpha
Xylaria polymorpha
Xylaria polymorpha, commonly known as dead man's fingers, is a saprobic fungi. It is a common inhabitant of forest and woodland areas, usually growing from the bases of rotting or injured tree stumps and decaying wood. It has also been known to colonise substrates like woody legume pods, petioles,...
(Pers. ex Mer.) Grev. (Ascomycetes) has been known to bleach wood, but is unique in that it is one of the few fungi that will erect zone lines without any antagonism from other fungi .
Spalting Research
Initial lab work was conducted on spalting in the 1980s at Brigham Young UniversityBrigham Young University
Brigham Young University is a private university located in Provo, Utah. It is owned and operated by The Church of Jesus Christ of Latter-day Saints , and is the United States' largest religious university and third-largest private university.Approximately 98% of the university's 34,000 students...
. A method for improving machinability in spalted wood using methyl methacrylate
Methyl methacrylate
Methyl methacrylate is an organic compound with the formula CH2=CCOOCH3. This colourless liquid, the methyl ester of methacrylic acid is a monomer produced on a large scale for the production of poly .-Production:...
was developed in 1982 , and several white rot fungi responsible for zone line formation were identified in 1987 . Current research at Michigan Technological University
Michigan Technological University
Michigan Technological University is a public research university located in Houghton, Michigan, United States. Its main campus sits on on a bluff overlooking Portage Lake...
has identified specific time periods at which certain spalting fungi will interact, and how long it takes for said fungi to render the wood useless . Researchers from this university also developed a test for evaluating the machinability of spalted wood using a universal test machine.