Cotton or polyester thread - which one? As a general rule, polyester thread is used on synthetic fabrics and cotton thread for cotton fabrics, so that they age well and wash similarly. However, many seamstresses swear by polyester thread and others by only cotton. Whatever the choice, for machine use, the same thread should be used for both the bobbin and the spool.
Here our Fil Au Chinois range on 100m spools.