A database of metallic materials emissivities and absorptivities for cryogenics

•Database of 58 thermal emissivities and absorptivities measured from 20 K up to 320 K is presented.•Data were systematically collected in our laboratory by a single measurement method and apparatus.•Database covers metallic samples, alloys, foils, coated metals and a condensed water layer on Al.•The effects of material and the surface finish on its emissivity or absorptivity are summarized. The paper introduces a database of low temperature total hemispherical emissivities and absorptivities of various metallic materials obtained from measurements conducted in our laboratory. Both quantities are measured in dependence on the temperature of thermal radiation starting at 20 K and ending between 120 K and 320 K. The database contains 58 results from measurements of 45 different samples such as bulk metals, foils and coated plastic or metallic surfaces. The database includes samples with surfaces finished by mechanical or chemical polishing, fine turning, sand blasting, abrading, etching and gold deposition and covers to some extent effects of material purity and surface aging. The dataset of all measurements has been published in Mendeley Data repository and is freely available online. Presented values of thermal absorptivity or emissivity are thus easily mutually comparable and provide a useful basis for calculation of radiative heat flows and thermal design of cryogenic devices.