Abstract: A core or insert primarily for the production of metal and alloy castings, e.g. of complicated internal shape, is a refractory body comprising essentially a water-soluble salt and a calcium silicate, the calcium silicate being present in amount of at least 45%, by weight, based on the total weight of calcium silicate and water-soluble salt, and the water-soluble salt and the calcium silicate having a particular particle size distribution. The calcium silicate is preferably a wollastonite.The core may be removed from the cast or moulded article by dissolution in water.

Abstract: A fired ceramics compact for use in casting of a super alloy material consisting of a solid solution of BaO and Al.sub.2 O.sub.3 wherein the composition of the solid solution lies on or between a first and a second eutectic composition, the first and the second eutectic compositions being adjacent and occurring to either respective side of stoichiometric BaO.Al.sub.2 O.sub.3 in a phase diagram of the solid solution.

Abstract: A refractory mould core for producing metallic castings of complicated internal shape formed from a water-soluble salt having the following particle size distribution:100% by weight of the particles have a size less than 750 .mu.m;90% by weight of the particles have a size of 8-600 .mu.m;80% by weight of the particles have a size of 5.5-500 .mu.m;70% by weight of the particles have a size of 4-400 .mu.m;60% by weight of the particles have a size of 2.8-350 .mu.m;50% by weight of the particles have a size of 2.0-280 .mu.m;40% by weight of the particles have a size of 1.6-220 .mu.m;30% by weight of the particles have a size of 1.0-180 .mu.m;20% by weight of the particles have a size of 0.3-160 .mu.m;10% by weight of the particles have a size of 0.1-125 .mu.m.