polyurethane as binder here the polyether resin component is admixed with a catalyst whose reactivity and or concentration based on the amount of resin leads to a time delay in commencement of the curing reaction the reaction rate of the curing reaction can also be adjusted for example by appropriate formulation of the resin components the adjustment of the reaction rate is carried out independently of the adjustment of the commencement of the curing reaction furthermore the use of cold cure processes using raw materials other than polyurethanes is also proposed for example cold curing binders in the form of acid curing or s 0 2 curing systems based on for example furan resins or phenolic resins are suitable these binders are by nature brittle so that springback on opening the mould is avoided and the resulting green body has a high dimensional accuracy a further advantage is that the systems can be made slower so that curing occurs after a greater delay than in the case of polyurethane systems this leaves more time for filling the mould a longer pressing time is then sometimes necessary mixtures of the polyurethane systems just described with cold curing phenolic resins are also conceivable as cold curing binders the ratio of polyurethane system to phenolic resin is advantageously from 5 1 to 1 1 a.