What's worse is that something, I assume tar, actually seeps in everything. I was looking at a house on a particularly hot day once, and the bedroom walls were

What's worse is that something, I assume tar, actually seeps in everything. I was looking at a house on a particularly hot day once, and the bedroom walls were 'bleeding' some weird black substance. I informed the owner, who exasperatingly told me he's been scrubbing them down for weeks but it won't stop. Every time it got hot outside the walls would start again. Apparently his parents smoked heavily in that bedroom for decades.