A permanent marker or indelible marker is a type of marker pen that is used to create permanent writing on an object. In general, the ink comprises a main carrier solvent, a glyceride, a pyrrolidone, a resin and a colorant, making it waterproof. It 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, or ultraviolet reactive). Like spray paint, these markers contain volatile organic compounds which evaporate to dry the ink. Permanent marker is another name for "waterproof" marker.
The permanent marker was invented in 1952 by Sidney Rosenthal.
These markers are generally used on hard, non-porous surfaces, because instead of staining they form a surface layer that can be removed by high pressure cleaning or paint thinners and organic solvents such as acetone (which is in nail polish remover), xylene, or toluene. Isopropyl alcohol and ethyl acetate are preferred cleaners when used indoors, as their fumes are much less hazardous than toluene and xylene, the main components of paint thinner, or longer-chain hydrocarbons found in mineral spirits. Other common non-polar solvents include benzene, turpentine and other terpenes (which constitute essential oils of many plants with strong scents), most ethers, chloroform and dichloromethane, hydrocarbon fuels, and diacetone alcohol, among many others. Note that most of these solvents are very flammable, and/or their concentrated vapors are harmful to health.
Some markers are designed to be long lasting, for instance by having two inks, one specialized to resist solvents, and one specialized not to fade. These can be available in refillable form.
A permanent marker can also be removed by drawing over it with a dry erase marker on non-porous surfaces such as a whiteboard as dry erase markers also contain a non-polar solvent. Most dry-erase board cleaner solutions also contain effective organic solvents like 2-butoxyethanol which will do the job.
Use in Microscopy 
In addition to being used for labelling microscopy slides, permanent markers can actually be used to do a negative stain of a bacterial sample. This means the background is stained with the marker, but the bacteria are not. The bacteria can be seen because they are stained (lighter) while the background is unstained (darker).
See also 
- Ink composition resistant to solvent evaporation -- US Patent 7084191 Description. <http://www.patentstorm.us/patents/7084191/description.html> Date of Access: 2-4-2012.
- S. Woeste and P.H. Demchick. 1991. New version of the negative stain. Applied and Environmental Microbiology. 57:1858–1859.