Hello Suzanne,
Sewing silks or satin you will definitely need to adjust your tensions, if the material is puckering the tension is too tight, I would not mess about with the bobbin tension unless you can really help it, adjust from the top, make sure you have a size 9 ant-static needle and very fine thread something like a sylko 50 or 60, only adjust the top tension one number at a time, trial and error, it is the only way.
drivewithken@blueyonder.co.uk, July 2007