What is Shore Hardness in sealants?

Shore Hardness measures the resistance of a material to indentation. For joint sealants, we typically look at Shore A. A low Shore A (e.g., 20) is soft and flexible, good for high-movement facade joints. A high Shore A (e.g., 40-50) is harder and tougher, suitable for floor joints that must withstand foot traffic or trolley wheels. Specifying the wrong hardness leads to either joint failure (too hard) or indentation damage (too soft).