Prism99

I have used YLI nylon monofilament thread successfully in both top and bobbin for machine quilting. I read a lot about polyester thread being better, so I bought Superior Threads' Monopoly to try out.

I found the Monopoly to be less invisible than the YLI nylon; it seems to be a little thicker and it also seems to catch the light more. Regarding heat resistance, I put my Rowenta iron on its hottest setting and ironed both threads with as much intense heat as I could. Neither one melted or showed any signs of damage. I have read that nylon thread can yellow and become brittle over time, which I gather to be somewhere in the neighborhood of 12+ years, but I think that is only if exposed to light. I had a small quilt in a closet for over 10 years (honestly, I forgot about it) and there was no change at all in the YLI nylon thread it had been quilted with. I think some of the warnings about nylon thread are for older quality nylon and/or brands other than YLI and SewArt (the only two brands I would use for nylon monofilament).

There are tricks to using monofilament thread successfully. If you are going to use it as the top thread only, the biggest things to know are that you need to use a good quality thread net on the cone, you need to set the cone in a jar behind your machine and feed it to your spool pin from there, and you must reduce the upper tension -- usually at least 2 numbers. This is because nylon thread stretches if it is under too much tension. On some machines you might need to tape a safety pin to the top left of the machine as an additional thread guide; my machine doesn't need that, however. There are additional tips if you are going to use it in the bobbin too, but if you are using regular cotton thread in the bobbin you don't need those tips.

You ***must not*** use glazed thread in your machine, top or bobbin! It is meant for hand sewing only and can damage your machine, requiring a trip to the sewing machine doctor for repair (at a cost much greater than a spool of thread!).

Edit: Unless the quilt is largely light-colored, you will probably want the "smoke" version of YLI. It shows up less on medium and dark fabrics than the transparent version that we usually think of as invisible.

I just noticed your comment about your vision. Be aware that nylon monofilament is very difficult to see while you are quilting. You will probably want to plan out your quilting ahead of time. A meander would be the most difficult simply because you cannot easily see where you have been! If you want to do a meander, I would recommend marking it before starting to quilt (old white soap slivers work well for this, as the marking does not have to be precise -- it would just give you some guidelines to follow). Depending on the quilt, you might also have the option of quilting wavy lines -- very easy, especially if you have a walking foot; you just move the quilt from side to side as you sew and do not try to be exact.