The forming of bamboo mold, spores and mildew on the surface of bamboo canes is not uncommon, especially when bamboo is not 100% dry.
Surface mold on bamboo products will only occur once, maybe twice until the moisture content inside the bamboo canes is completely evaporated.
Bamboo species such as Phyllostachys aurea, are often treated with a flame torch (heat treatment) and thicker bamboos such as Guadua angustifolia are cured with a boron solution.
The heat treatment is applied to fresh, green bamboo which leaves more moisture content inside the canes after the treatment opposed to air dried (boron treatment) bamboo. That's why some finished bamboo products are initially more sensitive to mold forming.
What causes Fungus to Grow on Bamboo
Carbohydrates: Fungus originate from very fine, air-borne spores present in fruit bodies and cause biological degradation of bamboo. They nourish from the starch and other carbohydrates (sugar) that are present in bamboo culms. At an advanced stage, their damage will show on the surface of the bamboo.
Oxygen: Just as almost any other living thing on this planet, fungus needs to breath. Limiting that supply of oxygen will retard their growth. Some fungi though, can survive on very low levels of Oxygen as long as their is a high presence of moisture.
Moisture content: Fungi love humid environments! Moisture levels of 40 to 80% are ideal for their rapid growth.
Temperature: Fungus feel most comfortable at temperatures between 25°C to 35°C.
What Types of Fungi Attack Bamboo?
Surface Molds: These bamboo molds grow on the surface and at the cross-ends of bamboo culms. Although they look spectacular, they have no influence on the strength of the bamboo and can be wiped off easily.
Stain Fungi: These bamboo fungi can penetrate round bamboos from cross cut ends as well as from cuts at the nodes after removal of the branches. Attack is indicated by shades of blue/grayish-black discoloration on the surface in the form of spots and streaks. It reduces the aesthetic appearance but does not affect the strength properties of bamboo (except in severe cases of attack).
Decay Fungi: These bamboo fungi cause the most serious kind of damage and grow within the lumen of the cells. The enzymes either decompose only the cellulose and hemicellulose leaving behind the lignin leading to brown rot, or they decompose lignin leading to white rot (white rot is more common in bamboo than brown rot). Early decay is difficult to detect. Even before slight color change or weight loss becomes apparent, the strength properties are much reduced, in particular the impact and bending strength. Early damage can be characterized by dampness in bamboo. At later stages of deterioration the culm is soft to the touch and may be only a fibrous or powdery mass.
How to Clean Mold from Bamboo?
The most effective way to instantly remove mold on bamboo is a commercial product called Mold Armor FG502. Alternative methods with lemon oil or vinegar as described below could also do the trick.
Remove bamboo mold, white spores and mildew with a soft brush and clean up the area with a damp cloth. Use lemon oil or a solution of vinegar and water to remove the mold.
For bamboo furniture it is recommended to apply 3 coats of polyurethane after the mold is removed. This can be time consuming but will ensure the conservation of the furniture. Make sure though, to first clean the furniture with turpentine and to dry it out completely. If you don't, mold might grow underneath the polyurethane finish and cause blisters.