A freezer laboratory makes possible the growth and study of a variety of ice types difficult to find in nature. Such ice may simulate the frozen sea surface in paleoclimates or under special environmental circumstances. To understand the interactions between the ice type and Earth's climate, it is desirable to characterize both the physical properties of the ice and its spectral albedo. Albedo measurements made in nature are most useful when the surface can be modeled as a plane parallel, horizontally infinite domain and is uniformly illuminated by easily quantifiable incident illumination (either diffuse illumination under complete overcast or direct illumination under clear sky conditions). Albedo measurements of laboratory-grown ices can be fraught with uncertainty. Because of edge effects, nonuniform illumination, lack of control of incident illumination and the inability to quantify light fields, the estimated ratios of upwelling to downwelling spectral or broadband irradiances are difficult to interpret. To circumvent these problems, we have designed and built an ‘albedo dome’ for measuring the albedo of sea ice grown in a freezer laboratory. A 1.2 m diameter acrylic dome is placed over a 1000 L insulated tank. The dome creates a ‘sky’ for the incident illumination and supports fiber optic probes for viewing radiances backscattered from the surface. The interior of the dome creates a uniform approximately isotropic sky as it is illuminated from beneath and coated with a highly reflecting white paint. A baffled ‘sun’ is mounted at the center of the dome, immediately above the ice surface. The sun illuminates the interior of the dome exclusively; the ice surface receives no direct illumination. Downward-looking radiance probes are mounted at quadrature angles on the dome and used to measure radiance backscattered from both the ice surface and from a reflectance standard. Laboratory spectral albedo measurements for an ice surface intended to simulate cold (T < –23°C) sublimating sea-ice surfaces during Snowball Earth (~600–300 Mya) are presented. Optical and physical property measurements indicate that the formation of a hydrohalite lag deposit on the surface increases the albedo significantly above that of sea ice subject to routine seasonal melt processes.