In ANH, they used wooden poles modifed with reflective material to help create the white core. For TESB and ROTJ, metal poles were used instead as they were more durable and the rotoscoping process had advanced enough to forego the materials from ANH, which made it easier for the rotoscoping process to be done. For TPM and AOTC, colored aluminum rods were used. This created a more balanced weapon and made it totally easy for ILM to rotoscope the blades in. During the making of ROTS, carbon fiber rods were used, taken from the design of a fishing pole. This resulted in a sturdier pole, which didn't bend as easily and were much lighter. Thus the fights were faster, especially Anakin vs Obi-wan. The new rods were color coated for ILM's benefit.