![]() ![]() The main cause of staining through introduced causes, is Iron Staining.As the name suggests, brown rot is brown in colour Wood rot will also change the colour of timber, especially brown rot.The damage that they do over time is superficial as it usually effects the outer layer only. They tend to be a dark blue-grey or black in appearance, hence the term “Bluestain”. They thrive on the extractives and high moisture content of green timber. Sapstain or Bluestain moulds are usually an issue when the timber is freshly cut. ![]() Staining due to natural or introduced causes But in situations where they are controlled, such as in dry or coastal climates, they don’t develop fully so turn the timber a silver-grey.Ģ. These sugars act as a food source for moulds, which can be dark and blotchy in appearance. Exposure to UV breaks down the lignin into simple sugars.This process lightens the colour of wood. Exposure to rain bleeds out the extractives, including the natural pigments (quinones).There are two main mechanisms behind this: Weathering is the biggest single, and most important cause of discolouration. Exposure to weather, including UV and rain It is the most important structural component of timber. Lignin is the glue that holds the timber fibre together. They can be ‘extracted’ with a solvent such as water or mineral turpentine, hence the name.Īnother key component of timber that can effect it’s change of colour over time is lignin. Extractives have been discussed earlier in a few previous articles, but are the pigments, tannins, and other resins. However they can become important over time, as will be discussed later.Īll timber contains what are generally referred to as “extractives”. Quinones are the true pigments, as the polyphenolic compounds are clear. This is defined by a group of chemicals known as quinones and polyphenolic compounds. The colour of timber is caused by natural pigments. Chemical changes within the wood resins, or “extractives”īefore we get into the nitty gritty, we need to understand a few properties of wood that will effect the colour over time.Staining due to natural or introduced causes.Exposure to weather, including UV and rain.After all, this will assist with some of those decisions on what to do when building something out of wood. This got us thinking that this topic would make a great general knowledge post. Exposure to Weather | Sapstain Mould | Bluestain Mould | Iron StainingĮarlier this month (May 2016), Preschem was asked to give a presentation on why timber changes colour at the Victorian Woodworkers Association. ![]()
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