Translucent materials have the property of reflecting light beyond the illumination point due to subsurface light propagation in the material. These reflectance properties can be characterized using the bidirectional scattering-surface reflectance distribution function (BSSRDF), a radiometric quantity that is a function of spatial, angular, spectral, and polarization parameters. At very small scales, we have observed that Spectralon, a commercial material widely used as a diffuse reflectance calibration standard, can be regarded as translucent. This can generate measurement errors and limit Spectralon's reliability as a calibration artefact for instruments that measure optical quantities on very small surfaces. To characterize the translucent properties of Spectralon, we have measured its BSSRDF using an experimental setup based on a goniospectrophotometer with a spatial scanning system for detection. In the present study, we show that Spectralon cannot be considered an opaque material at small scales (below 1 mm). For instrument measuring on small areas, Spectralon can be used for calibration only when the illumination area and the observation area differ by more than 1 mm in radius.