The wedge test for chilling tendency of grey cast iron is considered to contribute more to practical control of metal quality than any other single test in the ironfoundry. It is a simple rapid pre-pour test and the result interpreted visually is meaningful to the practical foundryman with or without formal training in metallurgy. The main purpose of this paper is to introduce the wedge test to those not already making use of it and to explain the relationship between chilling tendency and the founding characteristics and metallurgical properties of cast iron. The paper also present the wedge test as an adjunct to the formal tests used by foundry metallurgists and engineers. Emphasis is laid on the speed with which the test may be conducted and its use in detecting off-specification metal in the liquid state so it can be either diverted or corrected before pouring.