Monofilament is a very fine thread and can be made from nylon or polyester. It is really down to personal choice but most of the blogs I read preferred nylon. You can also get it as clear or smoky. I had chosen clear. You need to take care when choosing your thread and make sure it is made by a reputable manufacturer such as YLI, Sulky or superior threads which will ensure the thread is very fine and pliable and feels really soft. It should also break easily as if it doesn't it can cut through the fibres on the quilt top, not something you want to happen after all your hard work to make it.
Without having done any research I had bought a reel of clear YLI nylon thread. It felt soft and was incredibly fine When I was setting the tension I found I needed to reduce the thread tension - this is because the thread will stretch. I also found I needed to reduce my needle size a little because the thread was so fine. I used my usual 50 wt cotton quilting thread in the bobbin. This combination worked well.
I had put my cone of YLI onto the upright thread pin of my machine purely because of the size of the cone. I found out this was the right thing to do. The spools made by the reputable manufacturers are straight wound so putting it in the upright position the thread comes off without twisting. Cones are usually cross wound and the thread needs to be lifted off the top of the cone to avoid twisting possibly using a cone stand similar to what I have for my overlocker machine.
With the rest of the quilting I had a few times when the thread broke but this didn't cause any serious problems. All in all I enjoyed trying a new technique and I love the final effect. I'm also using the monofilament to quilt my nine patch quilt.
If you haven't tried monofilament thread I would encourage you to try it on a suitable project as it could give you just the effect you are looking for.
Tonight I'm playing with my 1 1/2 inch scrappy squares as I have an idea in my head for a small quilt. I'll show you what I'm planning tomorrow.