Question about framing a print printed on 27 pound paper at costco
I went to a print shop and printed a historical map I wanted framed on 27 pound paper. The plan was to get it framed at Costco. The guy mentioned at the print shop 27 pound was better than 32 if I was just going to mount it behind glass. At costco, the person asked me if I wanted the print mounted on something first ( I forgot the exact term she used but i think it was on cardboard?). At the time, I asked her what the pros and cons were and she said pro was that the print was mounted on the cardboard and prevents waviness later on, con being that the print is permanently attached to this cardboard. Does anyone know what the backing or process she was talking about is called? And what do people here recommend? At the time, I said no to the backing. Would I expect waviness in the print later on if I didn't choose the backing? Thanks in advance.