Scrap Quilt Top Completed

Here is a partial picture of the completed quilt.  It is quite large - 93" x 110"  Yesterday, I bought a king sized cotton sateen bed sheet for the backing.  I was planning to snow dye the back, but when I got home, I realized I am out of soda ash.....so cannot dye it until I get some of that.  Usually, I purchase a big bag of soda ash from a pool supply store, but honestly, I am not doing all that much hand dyeing these days (I have been out of soda ash for nearly a year!)  I am not sure I need to purchase a 40 lb bag.  It is a special trip to a pool supply store (and I have to find out where, because I think they have relocated since I last purchased a bag).  I might just pick up a small tub of it from a hardware store that keeps supplies for hot tubs.