I am new to thread painting so I don't have any "set formula".....on this piece I used a variety of threads that included 100% polyester by Gutermann and 100% rayon by Sulky, both of these were 40wt. In the bobbin I used a 70wt bobbin thread, the needle was a 70/10 universal.....I made a practice sample duplicating the materials in my final piece and adjusted the tension before working on the final piece....