My opinion would be its the cotton thread. Most cotton thread is not strong enough by itsself to withstand the stress put on it. Make sure the starts and stops are well secure, and you might want to change to a cotton wrapped poly thread, which gives the look of cotton with the strength of poly.

I agree with Lori S. My first thought was if your needle size (eye size) was just a bit too small for the thread, the eye could have caused 'chaffing' of the thread which weakened it - especially if the thread was not a long staple thread (which I don't believe C&C is).

And again agree with Lori ... could be the length of the stitch if thread was pulled too tight while quilting. We're these quilts FMQ'd or quilted with a walking foot? The tension could also have been a little too tight.

Combination of all of the above - tension, wrong needle size, and stitched too taut.

If I were you, I would start by A) switching to a different thread, either a long staple cotton or a cotton wrapped poly. B) making sure you have the right needle size for the thread you are using and the task you are performing. You can find some GREAT info online about threads and needles - and their correlation to each other, often on the manufacturers web site. Check out superiorthreads.com for lots and lots of "threaducation" including needles. And while you're there - check out the thread they sell too - awesome stuff.

Sorry, I should've clarified:

It's the actual quilting that's breaking, not coming loose.
I quilted pretty close stippling on the newer quilt and on the older one it was no more than 2" apart.
They're both machine quilted.

Hmmm.... I use whatever thread I have at hand for machine quilting so can't clarify what brand... I have only one quilt that the stitches have broken a little on, and it's usually near the beginning or ending or a row of stitching. It is a quilt that we use as a picnic quilt & pull over us when it's cool etc.

I think I solved the mystery!! While lying in bed this morning, my youngest DD's cat jumped up on the bed. He's only 7 months old so we haven't declawed him yet. The vet was hesitant. Anyways, he jumped on the bed, twirled, lied down and then began kneading his claws and I could hear him scratch the fabric in my half awake grogginess!! So, I scooted him off the bed and sure enough, there's a little tear in the thread there, just like the other ones! Eeeeeekkkkkkk!

Good to hear the mystery is solved. My household has a cat who loves to knead --he is almost 14 yrs. So I have him now trained to just lie on a quilt, but to use a piece of fleece to knead. Happy Cat and Happy Quilter.

Sorry, I guess I didn't clarify. It's the actual quilting that was breaking, not the piecing. But, I think I've found the culprit. My DD's kitten was caught kneading my bed quilt early this morning and it snapped a few of the threads. So, he's locked out of the bedrooms at the moment and an appointment is being made for him to lose his claws in a few weeks.

Dear PS150, the cat did it. Your best friend, Fido

Just so you know, when they declaw a cat they cut off the whole last joint of their "finger."