Simplify the following text for a Grade 9 native English-speaking person.
Original: It is sometimes possible to identify portraits that have been painted from death masks , because of the characteristic slight distortions of the features caused by the weight of the plaster during the making of the mold .
Simplified: It is sometimes possible to tell if paintings have been copied from death masks , because shape of the face is changed by the weight of the plaster during the making of the mold .