Capacity of the casting material used of mapping and rendering the contours and profiles of the mold cavity. It is determined by surface tension, solidification behavior (solidification morphology) and the cooling rate.
If fluidity spirals are used for testing, the length of the fully outfed spiral is measured and specified as the fluidity value. That section of the spiral that is set apart from the mold wall, i.e. that is not fully filled is referred to as running length and is proportional to the mold-filling property. Consequently, great mold-filling capacities correspond to short running lengths.
For example, flake graphite cast iron has excellent mold-filling properties because it displays the least volume shrinkage of all Fe-C casting materials. This means that the mold contours on the castings are rendered clearly and accurately.