Hallo everyone I've cracked the bottom thread question! There is a product called The Bottom Thread produced by Superior Threads! I found it on a UK shop (Barnyarns) website. This is how it is described: If you can imagine a bobbin thread that virtually disappears as the top thread and bobbin thread harmonise, then you could well be thinking of 'The Bottom Line'.
This is an innovative bobbin thread for sewing with all types of top thread including metallics and designer threads. It's has a silk-like finish allowing it to slide, not grab, to form the perfect stitch. The Bottom Line is ideal for both machine and hand appliqué. The fine 60wt. thread disappears into the fabric resulting in perfect curves and sharp points. The lint-free, ultra-smooth surface prevents snagging and knotting. Due to its lint free quality, excellent colour choice and fine 60 weight, the Bottom Line is superb for heirloom sewing, fine lace work and intricate Trapunto. Result!
Cheers Brabant