What type of creosote is most difficult to remove from a chimney?

Glazed creosote is the most challenging type to remove from a chimney due to its hardened, glass-like characteristics. It forms when wood is burned at low temperatures, creating a sticky, tar-like substance that can build up on the chimney walls. Over time and with the right conditions, this substance hardens, making it exceptionally slick and difficult to penetrate with standard cleaning tools and methods.

In contrast, liquid creosote is still in a semi-liquid state, which makes it somewhat easier to remove since it hasn't fully hardened. Unseasoned creosote, while it can also be challenging, is generally in a more manageable form that can be scraped or brushed away more readily than the glazed variety. Loose creosote consists of flaky and loose particles, making it easier to clean from the chimney during a sweeping session.

Thus, glazed creosote represents a significant risk for chimney fires due to its inability to be easily removed, necessitating thorough cleaning and regular maintenance to ensure the safety and efficiency of the chimney system.