Saponification

The Soap Reaction

Alkali in substrate + ester linkages in alkyd binder = literal soap

Film becomes soft, sticky, smudges easily

Loss of adhesion within weeks to months

Substrates That Cause It

Prevention

Fix If It Happens

Efflorescence

What it is: White crystalline deposits on masonry surfaces
Cause: Soluble salts brought to surface by moisture migrating through masonry
Mechanism: Water dissolves salts → migrates outward → evaporates → leaves salt deposits

Diagnostic

White, powdery, often crystalline appearance on masonry
Test: dissolves in water (proves it's water-soluble salt, not paint or other deposit)
Often appears at lower portions of walls (where moisture migrates from grade)

The Fatal Mistake

DO NOT Just Paint Over It

Sealing efflorescence in does NOT fix the problem

Moisture continues migrating, just lifts the new coating off

Deposits return on top of the new paint or pop the paint off

Correct Fix

Identify the moisture source — grade, sprinklers, leaks, lack of vapor barrier
Fix the moisture source — drainage, flashing, vapor barriers
Allow substrate to dry
Remove existing salts — dry brush off; mild muriatic acid wash for stubborn deposits; thorough rinse
Allow to dry again
Prime with masonry primer
Topcoat

Mildew

Common Mistake

Correct Fix

Kill mildew with bleach solution (typically 3:1 water-to-bleach) or commercial mildewcide
Rinse thoroughly
Allow to dry completely
Prime if needed
Topcoat with mildew-resistant product if conditions warrant
Address moisture source if recurrent (ventilation, drainage, etc.)

Chalking

What it is: ultraviolet (UV) degradation of binder, leaving pigment as powdery residue
Normal aging: Some chalking over years is expected
Premature chalking: Cheap binder, wrong product for exposure, deep base overloaded with tint

Diagnostic

Fix

Yellowing (White Alkyd)

Color Fading

Tannin Bleed

Quick Chemistry Reference

Substrate Issue	Don't Use	Use Instead
Galvanized	Alkyd	Direct-to-metal acrylic, zinc-rich
Fresh concrete	Alkyd	Alkali-resistant masonry primer
Cedar/redwood	Latex direct	Stain-blocking primer first
Chalky exterior	Standard primer	Bonding/chalk-stop primer
Glossy oil trim	Direct latex	Sand + bonding primer + latex
Mildew area	Direct topcoat	Kill first, then prime, then topcoat

Study guide