In my search for an affordable fabric to start with, I found some muslin listed on Ebay.

This is what the seller says about it -

I am hoping to use it to make a cathedral window quilt. Would this be a bad choice for any reason?

For me personally I would rather stick with fabric of a known content- Muslin can be tricky(?) to begin with then throw in the uncertainty of content - nope - not for me, sorry

what about Joanns when it is on sale ?

Thin muslin is good for foundation piecing, but not sure about using it for regular piecing or backing :D:D:D

If you mean physically going to a Joanns store, I'll have to wait about a year to do that. They don't have any of those in Japan. Maybe I could find something from their online stores?

The only thing I ever used muslin for was doing a drape/pattern making.

I have found Muslin courser and rougher than cotton, I use a heck of a lot of it, plain, for foundation scrap piecing, backings for place-mats, wall-hangings etc; and bag linings

ditto

Light weight muslin may be to flimsy for piecing.

Thanks everyone :) So the muslin is out for this project then. The price was pretty nice though.

What does everyone think of a cotton broadcloth? Too heavy? The finished blocks will be 4 layers thick. I also don't know about the eventual cost. I will need somewhere in the neighborhood of 10 yards.

Actually for a CW it might be just perfect. If you use too heavy of a fabric to start with those quilts get really heavy.

Very. Cathedral Windows requires turning and using the bias. If it were my project, anything other than cotton would creep me out before I started it.