🤣 the plastic is a solid and only turns to liquid while it's coming out of the nozzle during printing and is then cooled back to solid , I meant not solid as in the volume is not totally filled with plastic with 3d printing it's possible to make parts with various degrees of infill , so you can print a shell with 0 infill meaning the inside will be totally hollow, if you print at 50% infill it's will be 50% hollow, for the prints in this post I used a 10% infill so the inside of the prints is 90% empty space !BBH