Judy H morningstar

Customer brought a Dream Big panel for me to longarm on my Millennium. Poinsettia - dark red, green, brown. As each stitch disturbs the fabric thread, there is a white mark / snag / line. It is because there is only colour (dye /paint) on just the top surface of the fibre , so any little movement shows the white base. I have tried the following: 100 weight thread (Invisafill), size 16 (3.5) needle, looser on frame, lower tension, slow down. Nothing is making enough difference to look acceptable. Has anyone else experienced this? Any ideas? Thank you!