Assess and prepare a coating substrate
Start with the actual support
An architectural coating is attached to an existing substrate or previous film, so preparation begins with identifying that material and its condition. Timber, ferrous metal, galvanized metal, mineral render, gypsum board and previously decorated walls do not accept identical treatment. Check relevant moisture, contamination, cohesion, adhesion, roughness and exposure. A surface can look clean while carrying a bond-breaking residue, or look dry while failing the specified acceptance test. Choose the test and criterion that belong to the actual material and coating system.
Resolve causes before hiding symptoms
Chalking is a powdery surface condition, while efflorescence involves deposited salts associated with moisture transport. Neither is automatically cured by covering it with the thickest paint available. Establish whether the existing layer is sound and identify the relevant moisture route or contamination before approving preparation. Softened wood, unstable plaster or a moving joint may require repair outside ordinary decoration. A painter must recognize that boundary rather than convert a cosmetic product into an unsupported structural repair.
Coordinate preparation and primer
Cleaning, appropriate removal, abrasion, filling, dust control and priming serve different purposes. A primer can equalize absorption, promote adhesion, inhibit corrosion or block certain stains, depending on its actual formulation. It cannot make every loose or incompatible layer suitable. Select the whole system using the product instructions, approved specification and a representative trial where appropriate. Drywall finish categories differ between systems and countries; a remembered class number is not a universal surface acceptance standard.
Verify readiness and preserve evidence
Record the location, material, test method, observations and relevant project criteria. Drying time, pH limits, moisture limits, abrasive grade and cleaner dilution are product-specific rather than invented universal numbers. Older materials can contain lead, asbestos or other hazards; do not disturb them merely to identify a layer. Appropriate investigation and competent controls precede work. Preparation is accepted against the agreed finish, lighting and exposure conditions, not a promise that every surface will be flawless under any artificial inspection. These are written foundations, not authorization to sand hazardous coatings or certify a Danish or Swiss practical assessment.