Pressed glass and cut glass have similar beginnings when they're created. Both types of glass start off as molten glass pressed into a mold, but the mold used for each type is significantly different. A pressed glass mold — which can be made up of two to four different pieces — imparts the design directly onto the molten glass that is then cooled and removed from the mold. A cut glass mold does not impart any designs onto the molten glass. Instead, after the glass is cooled, the piece is hand-carved on a diamond wheel. There are a few things to look for to determine the difference between cut glass and pressed glass.
Look for seams. Glass that has been pressed in a mold often has easily visible seams, whereas any seams from the molding process of cut glass would be smoothed out before cutting in the design.
Hold the piece of glass up to the light. If it refracts light the same way a prism does — showing a rainbow — then it is cut glass.
Run your fingers along the designs on the glass. If the edges feel sharp, the piece is probably cut glass. The patterns in pressed glass are rounded and smooth to touch.