*This is from an earlier post - Updating Meg's original post dated 1/18/11
Petersham is a hard-finished, closely woven, cross-rib fabric. It is available in ribbon widths, and most commonly used for waist stays, facings and hat bands, among other creative uses. It is crisper than grosgrain, and gives structure and shape to areas of stress on garments and accessories.
Petersham ribbon, when used as a facing or support, is like a gift from the sewing gods! It kinda looks like regular grosgrain ribbon but its flexible picot edge allows you to shape it with an iron to curve and conform to your project, which grosgrain will not do.
Designers like Moschino, Tahari, MaxMara and Milly have used petersham ribbon as trim on their jackets and coats, and, of course it's perfect for no-waistband skirts and pants. If you make corsets, petersham can be of great use to you!
One great source for petersham ribbon in NYC's Garment District is Pacific Trimming on W. 38th Street. They have tons of colors in several different widths, very affordably.
Update: Just a word of caution that there is no sign or label indicating "petersham" ribbon at Pacific. The staff may not be able to point you in the right direction, so you just have to know what to look for: the edges of petersham have little scalloped ridges, whereas regular grosgrain ribbon edges are completely straight. In many stores, they will not know what you are talking about if you ask for it by name. Some stores will say they have it, but then offer something that isn't quite right - I have seen stores offer grosgrain as petersham, thinking the products are the same.