Polyester or cotton thread
 

I've been using king Tut cotton 40 wt thread to quilt, I just put a new quilt (100precent cotton) on and dark blue thread . I clean the machine and changed the needle but the thread kept breaking. I am also going to use a white so changed to that but the thread continued to break. I reloaded the machine with a green king tut of the same wt and the machine quilted great without any breakage. I then cut a piece from the blue, white and green thread to do a pull to break test. The white broke with little resistance , the blue took a little more to break but the green was the hardest to force a break. My question is why? Same brand, same wt. I have now ordered a polyester blue and white to use. I've read many articles on quilting with polyester but would like your input.

I prefer to use Rayon or Polyester thread. I have used cotton from Connecting Threads without any issues as well. Personal preference.....

I used to use Aurifil, but once I tried So Fine #50, I didn't look back. It's much stronger than cotton, very smooth and lint free, and the stitch quality on all of my machines that I've tried it on is tons better.

It dawned on me when I read this that when I switched to the So Fine, I also switched to topstitch needles, which I'm certain helped a lot, too. For me, it's a great combination; I haven't had any problems with thread breakage or poor stitch quality since.

could be age of thread. Once I had all sorts of trouble with a varigated blue thread. Changed thread, no probl. Also check for lint-my nemesis!

The dye often affects the thread quality. You often have problems with black thread. Sometimes it's so overdyed it's brittle and breaks easily. There's one brand where the black is so stiff, it keeps jumping out of the take up lever.

Is one newer than the other? Cotton breaks down over time so even with the same brand & same weight (or even the same color) you might get different results based on age. I've taken to labeling my spools with the month & year purchased to help me keep track of how old my thread is.

Cotton thread does lose strength over time and also when exposed to direct sunlight. You may be able to unravel some off the spool or cone and deeper down on the spool or cone it may be stronger. It isn't unusual for the same brand of thread to perform differently. The dyes also can affect the thread's strength and performance. Finally it is not unheard of that a manufacturer occasionally puts out a batch of bad thread.

Regarding preference... I quilt on a LA and I really dislike all the lint build up from cotton thread running through such a high speed machine. Inevitably, whenever I use cotton I end up with a lint blob in my bobbin case which throws off my tension. Some cottons are much worse than others. I still use cotton especially when I want a matte finish thread or need a color I can only seem to find in cotton, but I much prefer polyester for ease of use and lack of lint and I really like the shiny finish of many poly's that are marketed as embroidery thread. My go to thread is Filtec Glide but I also use many other brands and types. It all depends on the application. I will often use many different threads in one quilt.

I was told by my Bernina dealership to use Mettler silk finished thread in the 90s when I purchased my baby. I have had no problem thru the decades so I am still using this Mettler.