Selecting the right silicone sealant is critical for ensuring long-term durability, weatherproofing, and structural integrity in construction and industrial applications. A systematic evaluation prevents costly failures such as adhesion loss or substrate staining.

1. Chemical Composition & Compatibility
The first step is identifying the cure mechanism, as this dictates compatibility.
- **Acetoxy (Acid Cure):** Smells like vinegar. It cures fast but can corrode copper or etch marble and concrete.
- **Neutral Cure:** Odorless and non-corrosive. Essential for sensitive metals and masonry.
- **Oxime/Alkoxy:** Variations of neutral cure with specific safety or curing speed profiles.

2. Physical Properties
- **Movement Capability (**$pm%$**):** This is the most vital metric for joints. It defines how much the joint can expand and contract (e.g., $pm 25%$ or $pm 50%$) without cohesive failure.
- **Modulus:**
    - **High Modulus:** High tensile strength, suitable for structural glazing.
    - **Low Modulus:** More flexible, ideal for sensitive substrates like plastic to prevent stress cracking.
- **Hardness (Shore A):** Measures resistance to indentation.

3. Application & Adhesion
- **Tack-Free Time:** How quickly a skin forms. Fast skinning is good for vertical applications to prevent sagging.
- **Staining Potential:** For porous materials like natural stone (granite/marble), standard silicones can leach oil and cause permanent discoloration. Always check for "Non-Staining" certification.
- **Substrate Adhesion:** Verify specific bonding capability to glass, aluminum, concrete, or plastics without requiring a primer.

Summary
A robust evaluation checklist ensures the selected sealant matches the substrate's chemical nature and the joint's physical movement, guaranteeing a watertight and durable seal.