Question: Have you ever heard of third stage creosote? The creosote is so thick the brush won't clean it out. Any tips?? Answer: A couple of choices. This is glazed on, so you cannot easily scrape it off. You should start immediately using the chemicals which you spray on your wood to reduce creosote. ACS is one common brand. This turns the glaze to a easily cleaned powder over a period of time. However, if your class 3 creosote is thick and therefore dangerous, you might have to hire a professional to use special chemical solutions to remove it.