Am going to say smaller sharp needle.. not universal, not ballpointed, but sharp. (presuming your cottons are WOVEN cotton fabrics. And a small size... like size 11 or better yet size 9. adding fusible to the back first wouild help too. Fray check painted along the line and allowe to dry would help hold that spot together, there is a newer product from the company that makes fraycheck I think... that is softer and still holds loose threads together. I can see having some problem in some spots with some fabric but not a lot of spots and lots of fabric areas... I suspect the size and non-sharpness of the needle.... good luck hehehe