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Common Paint Defects

Defect – Brush marks

Causes

  1. Improper flow of the applied coating. Applying paint at high viscosity. Continued application over a long period.
  2. Application with a dirty , clogged brush.

Prevention

  1. Apply paint at the correct recommended viscosity using correct thinner
  2. Apply paint quickly and evenly
  3. Use clean good quality brushes

Cure

  1. After the coat has dried, rub down the surface to smooth and uniform level and Carefully recoat.
  2. Defect – Chalking

Defect – Chalking

Causes
Under bound coatings chalk on exposure to weathering Paints applied over insufficiently sealed, porous surfaces Paints not correctly pigmented for specific end use

Prevention
Ensure complete sealing of porous surfaces Avoid using inferior quality paints Do not mix undercoats into finishes

Cure
The fine powdery film can be removed by wiping and apply a fresh good quality Top coat

Defect –Sagging

Causes
Applying coatings at incorrect viscosities, film thickness Using improper thinner for thinning

Prevention
Care should be taken to apply coats at recommended film thickness and Application viscosities

Cure
Rub down the sagging parts and recoat carefully

Defect – Drying not proper

Causes
Application in unsuitable weather (frosty, cold, humid etc.)Improper ventilation Applied over oily, greasy, or unhardened surfaces Using long stored paints in which there are chances that the driers are absorbed by pigments making them non functional.

Prevention
Always apply in a dry, warm climate with sufficient air circulation Ensure proper cleaning of the surface free from oil grease Add slight excess of cobalt and lead drier

Defect – Efflorescence

Causes
Soluble salts from the substrate brought to the surface by solutions of fresh coats

Prevention
Do not apply coats on damp moist or freshly plastered surfaces , highly alkaline plasters

Cure
Wipe off the deposited salts completely from the surface and ensure no more deposition before recoating

Defect — Flaking

Causes
Surfaces having non uniform expansion and contraction causing undue stress Application over powdery or chalking undercoats Application over dirty greasy surfaces

Prevention
Ensure that all surfaces are thoroughly clean and dry surfaces. Use the recommended primers and undercoats.

Cure
Remove all loose paint by scraping and sanding

Defect — Peeling

Causes
subsequent coats before the previous coat has cured Application of paints containing strong solvents which softens the previous coat

Prevention
Ensure that the previous coats are thoroughly dried The primer, undercoat and top coat should be entirely compatible

Cure
Scrap the entire disintegrated system and rework freshly

Defect – Loss of gloss

Causes
Application on greasy, oily surfacesUsing inferior quality non compatible thinnersApplying over badly prepared porous surfaces and inferior uncured undercoats.

Prevention
Ensure that the surface is well prepared, free from dirt, oil, grease etc. Apply over good quality primer undercoat and under warm dry atmosphere.

Cure
Add small proportion of cobalt drier or antiskin agents.After flattening the surface, apply a fresh coat of top coat of clear varnish.

Defect – Low coverage

Causes

  1. Thinning beyond recommended volume.
  2. Recommendation wrt number of coats not followed
  3. Surface preparation i.e. primer / putty not as advised

Remedy
Adopt painting guidelines as specified in the product literature / container

Cure
Add small proportion of cobalt drier or antiskin agents.After flattening the surface, apply a fresh coat of top coat of clear varnish.