I am sure Stern's ghosting is caused by a few contributing factors. However, I cant tell you how many times I have seen the Stern "tour" videos they post on FB and very early on in the playfield assembly process they have some worker pounding away on top of a freshly coated playfield with a big mallet (probably to install some sort of T nuts or something). I can guarantee that this process is at least 1 of the contributing factors. There has to be a better, non violent, way to do what ever it is they are doing to these freshly cleared playfields. Here is a link to one of the videos (and this is one of the least violent ones I have seen). You can see (and hear) him banging away around the 20 sec mark.