Well, I am by no means an expert. But I have spent hours upon hours researching thread and trying thread...and I am STILL trying thread out! For whatever that is worth, here is my advice on choosing a thread for your quilt project.
#1. Determine the Use
Are you making a utility quilt? A baby quilt? A bed quilt? Are you putting your quilt in a show? Is it going to be a wall hanging? The first step before choosing a thread for me, is determining the use. For example, if I'm making a quilt for my daughter that is going to be washed a hundred times and receive a lot of abuse...I'm not going to use the same thread or other materials that I would a show quilt. I'm going to want my thread to be strong and in most cases I'm going to use cotton, cotton wrapped poly, or a polyester that has been treated to look like cotton. For cotton quilts, any three of these threads will provide enough strength to hold up to the quilts intended purpose and age nicely and evenly. For a show quilt, I might use a less sturdy 2 ply polyester piecing thread because it is strong and thin and will help me achieve excellent accuracy. A quilt like this would be a cherished heirloom in my home that would be on display but receive little use and few if any washing. So for me, it is important to determine the use before choosing the thread.
#2. Determine the Desired Effect
For a bang around quilt it may not matter to you the thickness of the piecing thread. So piece away with whatever is handy. I prefer all cotton for bang around quilts...and I like to quilt those with cotton thread too. The reason is these quilts get better with age. I love the look of a nice old aged quilt. But if you plan to chuck that quit in the trash when it is worn, well use whatever you like. Be aware that in general, polyester threads are more colorfast than cotton, so your quilt fabric is going to age a bit faster than that polyester. Choosing a matte or cotton covered polyesters are a great way to take advantage of the strength of polyester yet counter that uneven aging. If that doesn't matter to you, then quilt away with the poly of your choice! If you want it all to age together, you may choose to stick to all cotton quilts.
#3. Determine Your Budget and What's Available to You
So, you love pricey high end threads but you can't afford to quilt with them all the time. Remember that high end threads are often very similar if not exactly the same as threads that are readily available to you by other names. Often high end thread brands create these threads with quilters in mind, but truly are just perfecting thread that is already in existence and marketing it to quilters. Many threads whose original purpose was something other than quilting have been used with great success in quilts. The big name thread companies have caught on to this and capitalized on it too! There's nothing wrong with that either, but don't get too caught up in using the "right" thread. Instead focus on the right thread for YOUR purpose, and your budget. There are a few threads that common sense will tell you to avoid, like upholstery thread or hand quilting thread because it doesn't usually run through your sewing machine well - but most quilts hold up for many many years even if the "proper" thread wasn't used.
Note: My blogging pal Michelle asked me what my preferred thread is. To be honest that is a REALLY hard question to answer. I haven't tried all the threads on the market, but I have had many many threads that fit the bill for a particular project. I have a few go to threads...right now they are Isacord and Coats and Clark polyester embroidery threads. Both are affordable, come in colors I like, and sew up in a way that I really like. For piecing I generally use Essential Threads Cotton because of the color selection and affordability. For my most special projects I use several of Superior's threads. They are pricey, but they have a variety and color selection that is unmatched by their competitors But that doesn't mean it's what I will ALWAYS use. As I try out more thread, and I fully intend to because I just LOVE thread, these favorites may change! The best way to determine what's right for you, is to try it!