Creosote is a natural resulting pollutant from burning wood. It is, according to Dave Johnson, an expert at Hearth.com, a "gummy, foul-smelling, corrosive and inflammable substance that, if no precautions are taken, will coat the insides of everything it passes through. It is formed when volatile gases given off in the burning process combine and condense on their way out of the chimney." Creosote is the cause of most chimney fires.
Control and Prevent Creosote
The best "homemade" way to clean up creosote is to not let it build up to begin with. If you are using a wood stove, it is important to get the stove up and running very hot every morning. Burning it very hot will burn off any small amount of creosote that built up as the stove smoldered overnight. It is very important that you are certain the chimney is clear at the beginning of your heating season. Have it professionally cleaned if you are uncertain how to do it correctly. Any creosote buildup that's been left from last year can ignite and cause a chimney fire.
Burning dry wood will also help prevent creosote buildup. Wood that is left out in the elements or is "green" will burn slower and will create more creosote.
Cleaning Up Creosote
Clean smaller amounts of creosote that have built up on bricks or on the inside of stove glass with a paste of baking soda and water. Dawn dishwashing liquid has also been used very effectively for this purpose. For thicker buildup on glass, a metal scraper will work well, with the baking soda paste to finish.
Cleaning a chimney requires special brushes made for the purpose. They can be purchased to fit your stovepipe at most wood stove stores and some hardware stores. Glazed-on creosote generally requires industrial strength cleaners used by a professional.