Defect – Brush marks

Causes

  • Improper flow of the applied coating.

  • Applying paint at high viscosity

  • Continued application over a long period.

  • Application with a dirty, clogged brush.

Prevention

  • Apply paint at the correct recommended viscosity using correct thinner.

  • Apply paint quickly and evenly

  • Use clean good quality brushes

Cure

  • After the coat has dried, rub down the surface to smooth and uniform level and carefully recoat.

  • A 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

  • AWipe 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

  • ARemove 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 surfaces

  • Using inferior quality non compatible thinners

  • Applying 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

  • Thinning beyond recommended volume.

  • Recommendation wrt number of coats not followed

  • 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.