Abstract: Shell cores and molds are prepared more rapidly by the shell process using resin coated sands wherein the resin is a phenol-formaldehyde novalak resin but having a small amount, e.g. about 1 to about 10 percent by weight, of resorcinol incorporated therein whereby a significant reduction in the cycle time required to produce the cores or molds is achieved.

Abstract: An apparatus for pneumatically classifying non-uniform materials such as mineral particles and mine run materials which contain sizes ranging from relatively course particles down to fine dust. The apparatus includes a closed housing wherein a controlled air flow rapidly and efficiently classifies large quantities of material which pass through various classifying stages. The housing is provided with a system to remove and collect fines or dust from the housing which are created during the classifying operation on many types of material. The removal and collection system functions to withdraw a portion of the flow circulating in the housing and through the operation of a precipitator removes fines for collection whereby particle free air is returned to the controlled flow without disturbance to the classifying process.

Abstract: An improved molding composition comprising a refractory sand, clay and water. The sand is coated with a thermo-plastic resin prior to being mixed with the other components of the composition.