Silicon carbide was hot‐pressed to uniform densities of the order of 98% of the theoretical density, with slight additions of aluminum and iron aiding in this densification. Other elements having some effect were lithium, calcium, chromium, zirconium, and boron. This dense silicon carbide had very high strength at high temperatures; for example, it had a modulus of rupture of 70,000 1b. per sq. in. at 2500°F.