All standard gloss meters are designed for flat surfaces, if they are used on a curved surface, the measurement beam is reflected away from the instrument detector resulting incorrect readings. The more curved the surface the greater the error.
The solution to this problem is to using a very small area. The light is slightly scattered by the curved surface, however as long as the reflected beam remains sufficiently narrow to remain within the instrument detector the reading will be correct. The Novo-Curve gloss meter has been designed for this purpose and is specified for measuring cylinders and spheres with very low diameters. The Novo-Curve was developed in conjunction with the National Physics Laboratory (NPL).