for quilting I use cotton but, for embroidery I normally use rayon for the shine. That being said, all the professionals will tell you and I agree if you are going to wash it alot then go with poly because it holds up better. I use cotton on my quilts because its suppose to last over time better, cotton with cotton, where poly would eventually start cutting thru the fabric. I don't know if that's true but I went with it. I've heard lots of people using poly but I'd go with what I felt comfortable with. Maybe switch with the next quilt and use this one as a test to see how it holds up

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*** I hand quilt and use both cotton & poly .
*** They both work for me.
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*** I do not think I have mixed them before.
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as far as machine piecing and machine quilting -

I used cotton-covered polyester Dual Duty thread - I have several quilts that are in "active duty" and have been washed many times (the bindings are frayed!) - there is absolutely NO - NONE - cutting of the threads of the fabric that I can sec. All the seams are fine - no "cutting" of any threads there, either.

I don't know or understand how that belief started. I do not have experience with 100% polyester thread.

If one wanted to follow that "cotton only" usage - than only none-scrimmed cotton battings should be used, etc.

I would finish that piece with he thread I started with - especially if 95% done now!

Hand quilting thread is thicker----waxed............I once belonged to a group of hand quilters who took regular cotton thread and dipped the spools in wax before using......

When I hand quilt I buy the handquilting thread........

There is also another waxed thread for beading....silamide...thinner,...great for hexies.......stronger, does not fray as easily

I use Coats and Clark handquilting poly/cotton blend for all my hand quilting. It's basically the only handquilting thread available at local stores, and it works for me. My quilts are made to be used and I have had no trouble with it being durable enough for everyday wear and tear.

Yes, Hand quilting threads are thicker and have wax in them the aid with movement through layers and help prevent knotting. A piece of information - please don't use hand quilting thread on your machine. The wax will gunk your machinery!

I asked my Mom what they quilted with. She was a teenager in the '30s. She said they used all cotton when she started quilting, then during the war the cotton thread they could buy was terrible so they started using C&C cotton wrapped poly sewing thread but doubled the strand. It worked just as well as the old cotton quilting thread and lasted just as long. She's never used the waxed quilting thread.

I read an article not long ago about how many times we could wear clothes between washings. I don't remember the number but the gist of the article was that we wear fabrics out washing them more often than necessary and our fabrics (thread included) would last much longer if we washed them less frequently. Machine agitation grinds the fabrics, and dry cleaning solvents are especially hard on fabrics.

I use polyester for piecing and everything else by machine. For quilting itself, I use cotton thread whether by machine or hand.

I always use cotton hand quilting thread for hand quilting. No poly in my quilts.