Mixture and method for preparing casting cores and cores prepared thereby

Casting cores are fabricated from a mixture comprising a molten salt having dispersed therein a particulate material which includes a first refractory material having a mesh size of 60-120 and a second refractory material having a mesh size of at least 200. The salts are preferably halides, carbonates, sulfates, sulfites, nitrates or nitrites of Group Ia and Group IIa metals and the refractory material may be selected so as to be non-reactive with the molten salt. Some preferred refractory materials include alumina and magnesium silicate.