As called invisible and nylon, monofilament thread is an exactly that-one long filament, rather than small pieces twisted together. Even though it is often called nylon thread, it can also be made of 100% polyester. Monofilament thread is used in places where you want the thread to be invisible or as inconspicuous as possible. In general, it's for any project where you want the thread to disappear.
Where to Stitch with Monofilament Thread
Monofilament thread is great for stitch-in-the=ditch quilting so if you accidentally miss the ditch, your stitching will not show. It's also good for free-motion stitching where you want the stitched texture, and not the thread, to show on your project. If you are quilting a multi-colored quilt, the monofilament is perfect because it blends with everything. Invisible applique is also a technique for using this thread, as it truly does make it invisible.
How to Select Your Thread
Historically, monofilament thread has presented challenges and frustration when using it for sewing machine stitching. It was thick and resembled a fishing line, creating stitching problems for most sewing machines. However, today's monofilament threads are very fine, soft, and pliable. Even though it is strong when stitched into the fabric, this thread should be easy to break as you pull it from the spool.
How to Use Monofilament Thread
When sewing with monofilament thread, use a 60-70 weight needle because of the fineness of the thread. You'll want the needle to have a sharp point, such as a Microtex needle. The bobbin thread can be almost anything from lightweight bobbin thread to a 50-wt. thread. You may even use monofilament thread in the bobbin. If you do, wind the bobbin at a slow speed to keep it from stretching.
How to Adjust Tension for Monofilament Thread
If using monofilament thread in both the needle and the bobbin, there should be very few tension issues. When using cotton or polyester thread in the bobbin, you may need to loosen the needle tension slightly for quality stitching. Loosen the needle tension in small increments and test the stitch to see if it is what you want. Keep adjusting and testing until the stitch has the correct tension.
How to Thread Your Machine
Most monofilament threads are wound on the spool in a stacked formation. This means the thread should be set on the vertical spool pin with the foam pad under it so it can spin, feeding the thread without twisting. If it is a cross-wound cone, use a thread stand behind your machine and the thread will feed up without twisting. If the thread is spooling a the bottom of the spool, cover it with a thread net and pull the thread up and out of the net. Once you have the spool in place, you can thread the machine as usual except for the needle. Because of the fineness of the thread, it is usually easier to thread the eye of the needle manually, rather than use the needle threader.