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.
White Fire Retardant Muslin Fabric, Muslin Fabric
Cotton Voile Muslin fabric
Fire Retardant Egyptian Cotton Muslin Fabric - Soft White
Fire Retardant Egyptian Cotton Muslin Fabric - Soft White
WHITE - Egyptian Draping Muslin: Pure Cotton - for curtains and drapes
20 Yards of Soft Cotton Fabric, Muslin Fabric, Voile Fabric, White Cotton Fabric, Indian Fabric
EGYPTIAN COTTON MUSLIN White - 100% Cotton Fabric Drapes £5.99 - PicClick UK
Fire Retardant Muslin 100% Cotton Fabric Wedding Drapes
Alexandria Egyptian Cotton Fabric Ivory, by the yard
110 Inches Extra Wide 100% Long-Staple Egyptian Cotton Solid Broadcloth Fabric - Combed Cotton for Sewing DIY Crafting - Sold by The Yard (White)
100% Premium Cotton Muslin Fabric - Light Blue
Fire Retardant Egyptian Cotton Muslin Fabric - Soft White
Muslin Fabric 60'' Wide X Sold by Yard Cotton Unbleached White Printing Lining Upholstery Clothing Sewing Pattern Craft
Fire Retardant Muslin 100% Cotton Fabric Wedding Drapes