Which fabric finish is designed to add weight, stiffness, and firmness to the material?

The chosen fabric finish known as sizing is specifically intended to enhance the weight, stiffness, and firmness of a material. Sizing refers to the application of a substance that penetrates the fibers of the fabric, typically done before weaving or finishing. This process improves the fabric's body, making it more durable and giving it a more structured feel, which is particularly beneficial for certain types of garments and textiles where shape retention is important.

In contrast, the other options focus on different aspects of fabric treatment. Singeing is primarily used to remove fuzz and lint from the fabric surface, creating a smoother finish but does not contribute to the fabric's weight or stiffness. Finishing encompasses a broad range of treatments applied to enhance the overall feel or appearance of fabric but isn’t specifically aimed at adding weight or firmness. Dyeing involves adding color to fabric but does not alter its structural properties like stiffness or weight. Thus, sizing stands out as the correct choice for adding those specific qualities to fabric.