The interior walls of our 20 year old cabin, construction is just logs with rubber gaskets, show what look like drip marks. I can scrub some of them off, but don’t understand what they are, what causes them, or if they can be fixed.

Washed the walls with a vinegar, baking soda and ammonia with water mix and that helped a lot, but not completely.
Could you advise? many thanks, P. Venet

waterloop Changed status to publish April 8, 2024