Claim: Kovar, which is used in the construction of modern buildings,  and is used as a roofing material for airports, has a density of 80g /cm, hardness of 200-230 HV5, and Curie temperature of 900 °C.
Evidence: It finds application in glass-to-metal seals in scientific apparatus, and conductors entering glass envelopes of electronic parts such as vacuum tubes (valves), X-ray and microwave tubes and some lightbulbs. Kovar was invented to meet the need for a reliable glass-to-metal seal, which is required in electronic devices such as light bulbs, vacuum tubes, cathode ray tubes, and in vacuum systems in chemistry and other scientific research. Density g /cm 8.0 Hardness / HV1 160 Curie Temperature / °C 435