NDA Chemistry · Industrial and Applied Chemistry
Paints and Coatings
What each ingredient in a paint actually does — the pigment that colours, the binder that forms the film, the thinner that thins, the drier that speeds drying, and the additives (anti-skinning, antifoaming) that fix storage problems.
Why this matters
The chapter's hardest pocket — three of the four PYQs are HARD, all from 2019–2026, all asking the role of a specific paint additive. The win is one clean role↔example table: pigment = TiO₂, binder = silicones/resins, drier = metal naphthenates, thinner = turpentine, anti-skinning = polyhydroxy phenol, antifoaming = pine oil. Learn it cold.
Concept 1 of 2: Paint ingredients and their roles
Definition
The role↔example facts the bank tests:
- Pigment — gives colour and opacity. White pigment = titanium dioxide (TiO₂); blue/green organic pigment = phthalocyanine.
- Binder (film-former) — holds pigment together and sticks it to the surface. Examples: silicones, alkyd/phenolic resins (novolac), drying oils.
- Thinner (solvent) — thins the paint for application. Example: turpentine.
- Drier — speeds up drying by catalysing oxidation. Examples: metal naphthenates (cobalt, lead, manganese naphthenate).
- Anti-skinning agent — stops a skin forming on the paint surface during storage. Example: polyhydroxy phenol.
- Antifoaming agent — stops foam in emulsion paints. Example: pine oil.
| Role in paint | What it does | Correct example |
|---|---|---|
| Pigment | Colour + opacity | Titanium dioxide (TiO₂) TiO₂ is the standard white pigment; phthalocyanine is a blue/green pigment. |
| Binder (film-former) | Holds pigment, forms the film | Silicones (also resins / drying oils) Silicones are the binder; TiO₂, novolac and phthalocyanine in that question are pigment/resin distractors. |
| Thinner (solvent) | Thins the paint | Turpentine |
| Drier | Accelerates drying (oxidation) | Metal naphthenates Naphthenates are DRIERS, not thinners. Turpentine is the thinner. |
| Anti-skinning agent | Prevents skin in storage | Polyhydroxy phenol Anti-skinning agent = polyhydroxy phenol — not gelatin, pyridine or NMP. |
| Antifoaming agent | Stops foam in emulsion paint | Pine oil |
Practice this conceptself-check · 5 quick reps
The same idea in a real exam question:
Example 1 · Industrial and Applied Chemistry · Paints and Coatings
Turpentine is the thinner; naphthenates are driers
Binder ≠ pigment
Anti-skinning agent = polyhydroxy phenol
Concept 2 of 2: Emulsion paint additives — true/false facts
Definition
The emulsion-paint statements the bank tests:
- Pine oil is used as an antifoaming agent in emulsion paints — TRUE.
- Protective colloids INCREASE the stability of an emulsion — so 'protective colloids decrease stability' is FALSE.
- Driers containing oxidizable oils accelerate drying when added to emulsion paints — TRUE.
| Statement about emulsion paint | True or false | Why |
|---|---|---|
| Pine oil is used as antifoaming agent | True | Pine oil controls foam |
| Protective colloids decrease stability | False | They INCREASE stability Protective colloids stabilise the emulsion — they increase, not decrease, stability. |
| Oxidizable-oil driers accelerate drying | True | Oxidation speeds film formation |
Practice this concept3 quick reps
The same idea in a real exam question:
Example 2 · Industrial and Applied Chemistry · Paints and Coatings
Protective colloids INCREASE stability
Summary — formulas & gotchas at a glance
A revision cheat-sheet for the formulas and gotchas above. Click any concept name to jump back to its full explanation.
Reference tables (2)
Paint ingredients and their roles6 rows
| Role in paint | What it does | Correct example |
|---|---|---|
| Pigment | Colour + opacity | Titanium dioxide (TiO₂) TiO₂ is the standard white pigment; phthalocyanine is a blue/green pigment. |
| Binder (film-former) | Holds pigment, forms the film | Silicones (also resins / drying oils) Silicones are the binder; TiO₂, novolac and phthalocyanine in that question are pigment/resin distractors. |
| Thinner (solvent) | Thins the paint | Turpentine |
| Drier | Accelerates drying (oxidation) | Metal naphthenates Naphthenates are DRIERS, not thinners. Turpentine is the thinner. |
| Anti-skinning agent | Prevents skin in storage | Polyhydroxy phenol Anti-skinning agent = polyhydroxy phenol — not gelatin, pyridine or NMP. |
| Antifoaming agent | Stops foam in emulsion paint | Pine oil |
Emulsion paint additives — true/false facts3 rows
| Statement about emulsion paint | True or false | Why |
|---|---|---|
| Pine oil is used as antifoaming agent | True | Pine oil controls foam |
| Protective colloids decrease stability | False | They INCREASE stability Protective colloids stabilise the emulsion — they increase, not decrease, stability. |
| Oxidizable-oil driers accelerate drying | True | Oxidation speeds film formation |
Watch out for (4)
- Turpentine is the thinner; naphthenates are driers→ Paint ingredients and their roles
- Binder ≠ pigment→ Paint ingredients and their roles
- Anti-skinning agent = polyhydroxy phenol→ Paint ingredients and their roles
- Protective colloids INCREASE stability→ Emulsion paint additives — true/false facts
Test yourself on Industrial and Applied Chemistry
10 past NDA questions from this chapter, timed at 10 minutes and marked the way the exam marks it. You see your score and every answer the moment you finish. Free to start.