158cm wide, fine quite open weave cotton muslin which has been made fire retardant. (And it works too.) Not absolutely transparent, it comes in white with a lovely soft hand.
Minerva Crafts Fire Retardant Muslin Fabric White - per metre
100% Egyptian Cotton Muslin Fabric White/Ivory/Cream Soft Craft Material 150cm
BLACK - Egyptian Draping Muslin: Pure Cotton for curtains and drapes
Premium Muslin Fabric - 100% Cotton - 150cm Wide – Hot Pink Haberdashery
110 Inches Extra Wide 100% Long-Staple Egyptian Cotton Solid Broadcloth Fabric - Combed Cotton for Sewing DIY Crafting - Sold by The Yard (White)
Fire Retardant Egyptian Cotton Muslin Fabric - Soft White
100% Premium Cotton Muslin Fabric - Natural
EGYPTIAN COTTON MUSLIN White - 100% Cotton Fabric Drapes £5.99 - PicClick UK
100% Egyptian Cotton Muslin Fabric White/Ivory/Cream Soft Craft Material 150cm
WHITE - Egyptian Draping Muslin: Pure Cotton - for curtains and drapes
110 Inches Extra Wide 100% Long-Staple Egyptian Cotton Solid Broadcloth Fabric - Combed Cotton for Sewing DIY Crafting - Sold by The Yard (White)
Natural Cotton Gauze Muslin for Dresses, Blouses, Curtains/thin Cotton Muslin Fabric for Baby Clothes/gauze Fabric for Summer Clothes
Fire Retardant Muslin 100% Cotton Fabric Wedding Drapes
100% Egyptian Cotton Plain Soft Muslin Cheesecloth Fabric Lightweight 60 Wide
Egyptian Cotton Muslin Fabric - Soft White