Softness

Softness is a material property describing the ease with which a substance deforms under an applied force. In physical terms, soft materials typically have low stiffness, low hardness, and high compliance, meaning they yield, flow, or rearrange easily when stressed. Softness can depend on time and temperature, as many soft materials exhibit viscoelastic behavior, showing different responses under different rates of loading or during prolonged loading (creep).

Measurement and characterization of softness involve multiple approaches. Hardness tests (such as Shore durometers) assess resistance to indentation, while elastic modulus or stiffness measurements quantify resistance to elastic deformation. For polymers and soft matter, rheological tests reveal how viscosity and modulus change with frequency or strain. In soft matter physics, collections of soft materials—polymers, gels, foams, colloids—are studied for their complex, often non-Newtonian behavior.

Categories and examples of soft materials include foams, gels, rubbery polymers, textiles, and biological tissues. Softness is influenced by composition, microstructure, temperature, and loading rate; many soft materials exhibit creep or irreversible deformation under sustained stress. Applications rely on softness for cushioning, impact absorption, tactile comfort, and conformability, as in packaging, footwear, upholstery, medical devices, and soft robotics.

Softness is frequently contrasted with hardness and stiffness, and with malleability or ductility. In everyday language, softness also conveys subjective tactile quality, which can shape product perception and usability.