Safe to use creosote log in RMH

So I’m trying to figure out why all of a sudden why my RMH isn’t drawing like it did before I left for vacation. Maybe my cob cracked around the barrel from being too cold (got down to -20 with wind chill while I was gone and the house isn’t heated another way but don’t think it got that cold in the house) but still a possibility. Another possibility is something is using the chimney as shelter. I have a light/camera cord to see up the chimney and noticed sticky residue which can only mean creosote. I bought a brush and a rod to clean the chimney but also bought a creosote log to help. Has anyone used one on a RMH and if so did you burn it before or after using a chimney brush?

Thanks in advance

Hi Diane,
If your stove was built to be super efficient, leaving no wiggle room for any spare heat to escape with just enough draft to make it run, I doubt the crack theory as being your problem... unless its a big one.
If so, a small amount of cob should easily fill it in.

As for the potential creosote buildup, I'm assuming your referring to the final vertical chimney where you saw it? If thats the case, your stove is not performing as it should or your not burning wood in it correctly. Perhaps you can get us a few pictures or link to your build to help us see what your working with.
Every RMH I've ever run does produce a powdery dull black fuzz, especially in areas where the gas flow slows or in corners. It easily can be removed and is not shiny or hard like creosote is.
Perhaps this is what your seeing? A simple brush cleaning and vacuuming should easily take care of that.

If you've ruled out a critter nest, when was the last time you cleaned it?
Ash buildup on top of the riser or manifold can easily pinch off these areas and cause draft issues.

damp wood is a good source of creosote