Went to clean out the last ash from the boiler and all the loose stuff came out fine and then ran into quite a thick layer of crusty hardened ash at the rear and some on the sides just below the "rails" in there. I got alot of it off but wondering if left would it cause damage to the wall of the boiler ? Seems like must have had more this year because I don't really remember having to do that much scraping the last two years.