Rebecca Freeman Rebecca Freeman @rebecca-freeman Lexington, KY ActivityProfile3DFriendsSpecimensGroupsForumsFiles Topics StartedReplies CreatedEngagementsFavorites Search replies: Forum Replies Created Viewing 1 post (of 1 total) Author Posts March 30, 2016 at 8:20 am #3657 Rebecca FreemanParticipant The way I always explain it to students is that to get a mold (internal or external impressions) you must have the original shell. To get a cast the shell must disappear first, leaving only its impression(s). Love the Grabau quote! Author Posts Viewing 1 post (of 1 total)