Question

for a heavier interfacing, what is the material of the fabric? is it 40% nylon $60 percent cotton or something?

Answer 1

I believe all interfacing is a synthetic material. They are all completely washable and dry cleanable and shrinkage is not a problem. Check these sites for more information.

http://www.needlepointers.com/displaypage.aspx?ArticleID=32654&URL=http%3a%2f%2fwww.simplicity.com%2findex.cfm%3fpage%3dsection%2fsewtips%2finterface.htm

http://www.denverfabrics.com/pages/sewinginfo/simplicity-sewing-hints/sewing-interfacing.htm