A permanent marker is a type of marker pen that is used to create permanent writing on an object. Generally the liquid is water resistant, contains the toxic chemical xylene or toluene, and is capable of writing on a variety of surfaces from paper to metal to stone. They come in a variety of tip sizes (ultra fine to wide), shapes (chisel point, bullet tip, and wide bristle), and colors (metallic, non metallic, or ultraviolet reactive).
Like spray paint these markers give off volatile organic compounds. Also like spray paint these types of markers are not truly permanent as they can be removed using high pressure cleaning or paint thinning solvents such as acetone, they can simply be painted over, or they can eventually be worn out by time. Although there are also permanent markers that are completely resistant to solvents and will not fade or wear out in time, such markers are primarily used in graffiti and are more common as liquid for refilling a marker. For example some have two inks, one specialized to not be able to be washed off, and one specialized not to fade. Permanent marker can also be removed using a dry erase marker on certain surfaces such as a whiteboard as it contains acetone.
Permanent markers are commonly used to mark the label side of CD-Rs and DVDs. This practice has been discouraged because it is believed xylene and toluene harm CD-Rs and DVDs. On the other hand, alcohol based markers such as Sharpies are said to be safer, with water-based markers being the safest of all.