I use many different Superior Thread products in my longarm quilting. Monofilament is clear thread. Monofilament thread can be the best choice for some stitch-in-the ditch applications. For example: When there are many color changes and it would be hard to select a thread to blend into the background. The question that comes up - is this safe to use? Will it hold up? This is an article written by Bob Purcell, Superior Threads.
EDUCATION: Monofilament threads I recently received an e-mail asking if invisible monofilament thread is iron safe. She had heard that it melts if ironed. That is a commonly asked question and most likely due to hearing sad stories of monofilament threads melting and damaging a sewing project. Here is the truth.
There are two main types of monofilament threads: nylon and polyester. Traditionally, most monofilament thread has been nylon. Nylon is strong but it has some negative properties for sewing thread. It tends to go brittle over time, discolors (yellows), and has low heat tolerance. Nylon melts at approximately 400 degrees F. Although most irons do not have a numerical temperature setting, many irons can melt nylon when set at medium or high heat.
The preferred material for monofilament thread is polyester. Polyester does not discolor, go brittle, or have a low melting point. Polyester melts at the 480 to 510 degree Fahrenheit range and most irons stay well below this temperature up to the medium heat setting.
Superior Threads offers MonoPoly. Monofilament invisible thread is 100% polyester, thus the name, Monofilament Polyester.
Another caution: Watch out for monofilament threads labeled as 100% Polyamide. That may lead us to believe it is polyester but polyamide is the chemical word for nylon. Dishonest labeling? No. Misleading? Yes.
Be safe and stay with polyester when using monofilament threads.