(((((((( I've seen granny squares with mixed yarn weights and materials and they do indeed shrink if cotton or wool where the acrylic won't; Sad looking critter, too.
A 'ghan would be still be good for other uses, though, just not for across the couch where you'd display your wonderful work and use for warmth.
I'd advise you to do this for granny squares, be it knited of crocheted:
Sort your materials separately into see-thru bags.
Within that sort, sort again by weights into yet another
bag for a bag - in - a bag system; Sort again for colors
and sort again if varieagated.
Once sorted, you can label the bags with a felt pen. As you make new scraps, run to your sorted system and store in there.
Once you have enough of one type, color, etc, buy the same for your MC.
For that matter, sort any of your yarn using this system. Ad in, as in tennis, on keeping materials clean (dust free, dander free, hair free, etc.) and also allows you to see what you own.
These can then be placed in stackable, non pulling drawer systems and you can see the contents and remove readily. The stackable, wire coated bins are ideal and I use them in closets for many other things.
Enjoy and welcome to the forum!
Hope this helps!
I am making a Granny Square Afghan to use up leftover yarn.
Is there a problem in mixing different types of yarn; like wool, cotton, acrylic, etc. If so, is the issue about how to clean it, or is there something else (like getting out of shape) that I'm unaware of?
Thanks for your help!