Originally Posted by Kaiser
What's going on here? Is it the precipitation of cold break. But 1 Plato difference is a lot.
I can't think what else it could be. I assume that your measurement practices are sound, since I know you're pretty experienced with the scientific side of brewing... Having not added or subtracted anything from the wort between the two samples, it has to be some physical change that occurred during chilling, and cold break is the very obvious culprit.
Considering how much cold break you can get with proper chilling, I'm not surprised that it would produce some noticeable change, and the numbers you've quoted don't seem COMPLETELY unreasonable to me as being attributable to cold break, but I certainly don't know enough to be sure.