Adhesion is the degree to which an applied layer bonds to the substrate. It applies to paint, glue, plaster, coating, sealant and tile adhesive. Good adhesion determines whether a finish stays put for years or, after a short time, flakes, peels or chips off.
What adhesion depends on
- Clean substrate — grease, dust, soap residue and loose particles prevent adhesion
- Dry substrate — moisture under the layer causes blistering and peeling
- Roughness — a slightly roughened or sanded surface adheres better than a smooth, dense face
- Absorbency — an overly absorbent substrate draws out water/binder too quickly; a non-absorbent (smooth) substrate offers little grip
- The right primer — bridges the difference between substrate and finishing layer
Improving adhesion
- Clean and degrease — remove dirt, grease and old, loose layers
- Sand — roughen smooth, dense material for grip
- Prime — use a primer that suits both substrate and finish
- Bonding primer on difficult substrates — for glass, tiles, plastic and metal
Points to watch
- Cross-cut/tape test — the adhesion of a coating is checked with a cross-hatch scratch test and adhesive tape
- Application conditions — too cold, too warm or too damp disrupts adhesion; follow the manufacturer’s instructions
Related terms
- Primer
- Glue
- Plaster base
- Adhesive mortar
- Substrate
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