the type of fabric has nothing much to do with a needle choice- the needle is decided upon by the thread being used. if you visit Superior Threads you can print off a chart that tells you what needle to use with what thread. I use a 14 when using invisible or silk thread, a 16 when using 60 wt thread, an 18 if using heavier thread- but it all depends on what the recommended needle is for the thread I have chosen. the free charts from Superior Threads are really great resources to have. they explain the differences in threads, needles for long arm, domestic machine & hand stitching...a great place to find answers to many questions regarding threads and needles.