Approximately what fraction of the mold's volume should each layer fill?

The ideal choice for the fraction of the mold's volume that each layer should fill is one third. This approach allows for optimal control over the material flow and helps in promoting even distribution during the pouring or casting process. When each layer is filled to about one third of the mold's volume, it mitigates issues such as excessive pressure buildup or uneven cooling, which can result in defects or inconsistencies in the final product.

Filling the mold with this fraction helps maintain a manageable volume of material at any given time, allowing for adjustments to be made if necessary, based on the characteristics of the material being used, including viscosity and setting time. Additionally, pouring in thirds allows for proper release of air bubbles, which could otherwise become trapped if the mold were to be filled too quickly or with larger amounts at once. This is particularly vital in precision applications where mold detail can be impacted significantly by air entrapment or uneven material distribution.