Use of 2 different threads
 

Can you use polyester thread in the bobbin and cotton thread on top? I was scared that the strength of the polyester might rip through the cotton. Any help would be appreciated, thank you.

It's fine to mix threads. Polyester thread today is made with similar tensile strength to cotton (as long as you are using reasonable quality threads).

One thread you don't want to use is rayon thread. It is just too weak to stand up to the use that quilts get.

What Prism said.

In the long run, cotton & poly break down at different rates and fade at different rates. If you are asking about 20+ years into the future, I am a fiber purist and believe in using all the same fiber for fabric, thread & batting. That said, cotton will start to break down around the 20 year mark & you will likely need to do restoration regardless of whether you mix & match fibers.

I did mix & match on my very first quilted projects & it held up fine for the first 15+ years even with improper washing (washing in warm, drying partway on medium heat). Yes, threads have improved during that time, but at the end of the day, polyester is a long-chain polymer and cotton is a natural fiber. Advances in the science of creating synthetic fibers has made poly threads that feel softer, that have smoother edges so as not to "cut" into natural fibers as much & that better mimic natural fibers straight off the assembly line, but as far as how it retains color & breaks down, it will always behave like a synthetic fiber. If you pick a red poly for one thread & a red cotton for the second, over the decades the red cotton will fade to a dull red & start to fray while the red poly is still nearly as bright as day 1 & almost as strong.

I use poly in the bobbin and cotton on the top more then any other thread mix.

I was taught to make sure the threads are the same weight or you need to do some adjustment to your tension.

It's true that cotton and polyester fibers break down at different rates and fade at different rates. The fading issue becomes obvious over time in quilts that are made with both cotton and poly fabrics; the cottons fade while the poly's remain vibrant. However, fading will not be an issue if the cotton and polyester threads being used together are white or cream-colored. The breaking down at different rates is probably also not an issue for piecing.

There are a lot of considerations that can be taken into account. I have done piecing with poly in the bobbin and cotton on top. On my machine, however, I noticed that the seams made with this combination did not lie as flat as seams with cotton thread both top and bottom. I noticed the same problem when piecing cotton fabrics with polyester thread both top and bottom. That's why I switched back to cotton thread both top and bottom for piecing. One other issue I noted when using poly both top and bottom for piecing is that I needed to be careful not to cut the threads too short. Poly thread stretches a little while sewing; cutting the threads as short as I do with cotton sometimes means I lose a couple of stitches at the very end (from the polyester thread springing back into the seam). The differences in thread combinations are subtle, but ones I appreciate, so using cotton thread both top and bottom for piecing makes sense for me with my current machine.

I recently took some classes with Jamie Wallen. He uses polyester thread exclusively for his machine quilting, in part because it stands up over time better than cotton thread does. The only time he uses cotton thread for his quilting is if the customer is a cotton purist and insists on cotton thread. Jamie said he has talked to many museum textile experts who have told him that they have many beautiful quilts in storage that cannot be brought out to show because the cotton quilting thread has dry rotted. This happens because most quilts end up being stored in less-than-ideal conditions (attics, basements) over time. The portion of the quilt most vulnerable to deterioration is the cotton quilting thread that holds the layers together. For hand quilting, I would never switch from cotton to polyester thread because it would be so much more difficult to work with. However, for machine quilting, it can make a lot of sense to switch from cotton thread to polyester thread.

There are so many options today, every quilter ends up making decisions about what they are most comfortable with. It used to be that the only "real" quilts were hand pieced and hand quilted with all-cotton components (mostly because those were the only options a quilter had!). Nowadays it's not so simple. There are many choices made at each step in construction, and each choice has pros and cons.

I usually use the same kind/type of thread in the top and bobbin threads because I think that "the same" will be easier to sew with as far as tensions go.

I have not done any experiments with "combinations" - so can't give any input on what might happen.

I think - when people do embroidery - they use two different kinds of threads a lot of the time.

If the stitching looks like you want it to - I am reasonably sure the sun will come up again the next morning regardless of what kinds of threads you use - and your seam will hold together, too.

I almost always use a poly bobbin thread along with a wide variety of top threads. To restrict yourself to only one you of thread is very limiting. I have used everything from 12 weight cotton to all types of 40 and 50 weight poly and cotton to metallics. The more difference in the top and bottom weight I'll mean you have to adjust the tension, but learning how to do that is key to advancing your quilting choices.

Pam

I mix threads all the time, both for piecing and quilting. I like to use prewound bobbins, and they usually come with polyester thread. I use cotton as my top thread. It works fine; the thread manufacturers make threads to be compatible nowadays.