Answer:

glassine

AnswerCrossword Clue
GLASSINEClear envelope material
GLASSINEClear, like an envelope
GLASSINEStamp collector's envelope
GLASSINEWater-resistant paper
GLASSINEKind of paper.
GLASSINENearly transparent paper
GLASSINEWindow envelope material
GLASSINEEnvelope material
GLASSINETranslucent envelope material