Originally Posted by CBW1999
Looking at the pictures as I read through the thread, I noticed that pretty much every thermometer shown, that had been used- has a build up of contaminants (seasoned). This will cause the thermometer to give false readings to some extent.
The heavier the contamination, the more fluctuation. As the contamination is uneven and acting as an insulator initially and then possibly a heat sink, I can see why it takes time for adjustments to be noticeable.
I think this normal build up you speak of is pretty negligible. IMO it would take several millimeters this gunk to cause concern as to whether it will cause any effect.