Originally Posted by IamMadMan
It could be as simple as the grate was exchanging temperatures with the meat sitting on it (heat is exchanged to the meat and the grate is being cooled by the meat) where the clothespin was allowing the guru to read the ambient air temperature being it was not touching the metal grate itself.
Makes sense to me. I'll use clothes pens on both next time and see what happens. Thanks for your advice on this. Sometimes the simplest things, I need laid out in front of me.