Abstract: Phosphosilicate compositions are disclosed for treating foundry molds and like products to enhance mold strength and refractoriness. The phosphosilicates, characterized more specifically as silicyl metaphosphates, may be used in combination with select refractory aggregates and other additives to form mold surface treating compositions, or may be combined directly with foundry sand or other comminuted refractory material for compacting into a mold form.

Abstract: Methods of preparing Hybrid Silicate Binders are shown by admixing the following materials:1. a basic or acidic colloidal silica sol suspended in water or glycol ether;2. an organic silicate, such as ethyl silicate, hydrolyzed with water;3. a mineral acid of sufficient quantity to produce a final binder having a pH of 1 to 4; and4. the hybrid binder contains silica sol and organic silicates such that the ratio of weight contribution of SiO.sub.2 from organic compounds to weight contribution of SiO.sub.2 from colloidal silica sol is in the range between 0.09 to .9, in the final binder.That is, ##EQU1## The final binder preferably contains about 18%-21% SiO.sub.2. If basic silica sol is used it must be added to a mixture of the other ingredients.The preferred binder has a shelf-life exceeding nine months, it can be chemically polymerized or air-set and provides high binder strength and refractoriness.