When the enterprise is not paying attention to the production and processing, it may encounter the phenomenon of wood discoloration. The specific analysis is as follows:

1 The color change of wood

Wood discoloration, in simple terms, is the color change that occurs on the surface due to the action of the environment (sunlight, oxygen, moisture, temperature) and microbes (fungi). Wood sawn timber and wood products may be discolored. After the trees are felled, the logs are prone to discoloration under the ends of the logs and under the intact bark. After the original processing, sawn timber (sheet, square) is also prone to blue, brown, mildew, etc. during storage and processing. After wood is made into wood products, discoloration may still occur during use. There are many kinds of wood color changes, from wood color (white/light yellow/light brown, etc.) to pink, red, blue, green, gray, dark gray, brown, taupe, dark brown,

Wood discoloration can be divided into two categories due to their different causes, one is chemical discoloration, including tannin discoloration and oxidative discoloration; the other is fungal discoloration, including mildew and blue (also known as cyanosis, edge Material color). Among them, fungal discoloration is more common, and the impact is more serious. Generally speaking, wood discoloration refers to the discoloration of fungi.

2 Chemical discoloration of wood

Wood of many species, when exposed to high moisture content or exposed to moist air for a prolonged period of time, can be discolored, not caused by fungal infection of wood, but by chemical reactions of certain components in the wood. , called chemical discoloration. Oxidative condensation of tannins, pigments, alkaloids, sugars, phenols and other organic matter in wood, the most important of which is the oxidation of phenolic substances in wood. Phenolic compounds have a benzene ring structure and are easily oxidized, which is the cause of chemical discoloration. Phenolic compounds are colorless before oxidation, some are soluble in water; after oxidation, they form water-insoluble condensates, the color is red, reddish brown, brown, so chemical discoloration is also called oxidative discoloration.

Some materials contain tannins, also known as plant tannins, which are a mixture of polyphenols. When exposed to iron under humid conditions, the tannins react with iron to form a tannic acid. iron. The iron tannic acid is black and is the main raw material for making ink, thus making the color of the wood black. Depending on the amount of iron and the length of time the wood is in contact with the iron, the color of the wood changes from light grey to blue-black. Similarly, this chemical discoloration occurs in wood when the wood is immersed in water with high iron content. In addition, the wood is in contact with copper or copper. Since the tannins in the wood react chemically with copper, the formation of copper tannins also discolors the wood (light red). Chemical discoloration often occurs during wood drying. This is mainly due to the slow drying speed of the wood, especially at the point of contact with the skid. The chemical discoloration is characterized by a shallow depth of discoloration and a uniform discoloration.

3 Mildew of wood

Moldy wood will discolor the surface and sapwood of the wood, but the mildew has a lighter range of discoloration, and its discoloration is caused by colored spores. Since the spores of mold only grow on the surface of the wood, the moldiness of the wood is limited to the surface of the wood or a layer that is very shallow near the surface.

Moldy often makes the wood green, white, black, and occasionally other colors. The discoloration caused by mold is often flocculated or spotted. In warm and humid climates, or in poorly ventilated environments, mold spores deposited on the surface of wood tend to proliferate and grow mildew.

The fungi causing moldy wood are Trichoderma sp., Penicillium spp., Aspergillus spp., Mucro, and the like. The most important species of Trichoderma fungus is Trichoderma viride, and the surface of the wood infected with this fungus is green. There are many kinds of fungi of Penicillium and Aspergillus, and common species such as Aspergillus niger. After the wood is infected with this mold, the surface is black spots, sometimes connected into pieces.

Molds have better adaptability and endurance to the environment and substrates than orchids and decay fungi. Molds are also highly resistant to chemicals and can grow even when exposed to certain toxic chemicals. Mildew can still be found on some anti-corrosion treated materials.

As a result of the mildew of the wood, the surface of the wood is only discolored, and the range of discoloration is shallow, so it can be removed by a brush or removed by shaving off the surface layer. Mildew has little effect on the quality of the wood itself. Therefore, it is usually not considered to be a defect. However, after the mold infests the wood, it can increase the permeability of the liquid to the wood. Thereby promoting the generation of blue.

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