Originally Posted by AnOldUR
I believe this is only true with glass. A plastic bucket has insulating properties that glass does not. The temperature of the inside of the bucket may not be the same as on the outside.
When there is a change in temperature, glass will reflect that change quicker than plastic. Its not as if the plastic is absorbing heat from the fermentation and holding on to it forever, it just taste a bit longer to transfer that heat. Once that happens, the fermometer will read an accurate temp.
I like your Jack-O-Lanterns!