The Superflite manuals call for a #2 Zahn cup in measuring the viscosity of the primer and topcoat, but with the conversions below, a #4 Ford cup is much less expensive viscosimeter. This cup is made of molded CAB plastic, and it’s designed to hook over the edge of the can while measuring the viscosity of the liquid. Here are the proper #2 Zahn to #4 Ford conversions: 17 seconds in the Zahn cup is equal to 10.88 seconds in the Ford cup; 23 seconds in the Zahn cup is equal to 14.72 seconds in the Ford cup.