Large specimens of ceramic superconductors are difficult to solid-state sinter to full density, while maintaining superconductivity, without the high temperatures and pressures found in a hot isostatic press (HIP). HIPing can give highly dense, superconducting Bi2Sr2CaCu2O8 (Bi2212) and Bi2Sr2Ca2Cu3O10 (Bi2223) with only slight decomposition. If Y123 is HIPed to full density in a metal capsule, then the nonsuperconducting tetragonal phase forms as a result of decomposition. HIPing of CuO plus YBa2Cu3O7 gives highly dense, superconducting YBa2Cu4O8 (Y124), which is stable at high temperatures and oxygen pressures.