DMC - Petra Crochet Cotton Thread. These highly mercerized cotton balls are lustrous non-divisible and made from 100% cotton. Perfect for cross stitch needlepoint and embroidery on a wide variety of fabrics when a rich raised pattern is desired and for the finest crochet lace. Size: 5. Comes in a variety of colors. Each sold separately. Machine washable, dry clean, safe, iron, do not bleach. P Solvent Safe Dry Cleaner. Imported. Petra's yarn is combed, flame singed and twice mercerized which gives it its strength and softness. Petra yarn is a 2-ply 100% long staple cotton yarn. With its exceptional shine and softness. Knitting and crochet designs progress quickly and easily. Available in a variety of colors. Each sold separately. Machine washable, dry clean, iron safe, do not bleach. Imported.