length of the cork, the cork is partially pushed out of the bottle, or wine is visible on the top of the cork while it is still in the bottle, it has most likely been heat damaged. Heat damaged wines often become oxidized, and red wines may take on a brick color. Even if the temperatures do not reach extremes, temperature variation alone can also damage bottled wine through oxidation. All corks allow some leakage of air (hence old wines become increasingly oxidized), and temperature fluctuations will vary the pressure differential between the inside and outside of the bottle and will act to "pump" air into the bottle at a faster rate than will occur at any temperature strictly maintained. Reputedly, heat damage is the most widespread and common problem found in wines. It often goes unnoticed because of the prevalence of the problem, consumers don't know it's possible, and most often would just chalk the problem up to poor quality, or other factors. Lightstrike Lightstruck wines are those that have had excessive exposure to ultraviolet light, particularly in the range 325 to 450 nm. Very delicate wines, such as Champagnes, are generally worst affected, with the fault causing a wet cardboard or wet wool type flavour and aroma. Red wines rarely become lightstruck because of the phenolic compounds present within the wine that protect it. Lightstrike is thought to be caused by sulfur compounds such as dimethyl sulfide. In France lightstrike is known as "goût de lumière", which translates to a taste of light. The fault explains why wines are generally bottled in coloured glass, which blocks the ultraviolet light, and why wine should be stored in dark environments. Ladybird (pyrazine) taint Some insects present in the grapes at harvest inevitably end up in the press and for the most part are inoffensive. Others, notably the Asian lady beetle, release unpleasant smelling nitrogen heterocycles as a defensive mechanism when disturbed. In sufficient quantities these can affect the wine's odor and taste. With an olfactory detection threshold of a few ppb, the principal active compound is isopropyl methoxy pyrazine - this molecule is perceived as rancid peanut butter, green bell pepper, urine, or simply bitter. This is also a naturally occurring compound in Sauvignon grapes and so pyrazine taint has been known to make Rieslings taste like Sauvignon blanc. Microbiological Brettanomyces (Dekkera) The yeast Brettanomyces produces an array of metabolites