In my experience if a foundation fabric is used for a crazy quilt it's just muslin.. and the fabrics used for the top are "dressier" things. silk,, satin, velvet, etc. I've never heard of using chiffon or organza.. I think the chiffon would be too sheer and the organza would be stiff as a board. also the ones I have seen had a backing and were quilted and so the foundation fabric was not seen.