Optical Illusion

MrsB and I visited a craft makers village called Cedar Farm today, once a regular haunt but not sadly for a year or so. It’s undergone some massive improvements during the pandemic lull, which are very pleasing and makes it an even better place to visit.
One of the glass makers there has this vase on display, and it was only when I went to touch it that I realised it is actually hollow in the orange middle but not the white outer!