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.

All Industrial and Applied Chemistry notes NDA Chemistry strategy

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

Intuition

A paint is pigment + binder + solvent + additives. The bank gives you a role and asks the example, or gives an example and asks the role. There is exactly one correct match per row — memorise the whole table.

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

Try it yourself

Match each: (i) Pigment, (ii) Thinner, (iii) Drier, (iv) Anti-skinning agent — to TiO₂, turpentine, metal naphthenates, polyhydroxy phenol.

Practice — Level 1 (5 reps)

Quick reps to lock in the method. Try each, then check.

1.
What is commonly used as a white pigment in paints?
2.
Which paint ingredient is the binder (film-former) among TiO₂, novolac, phthalocyanine, silicones?
3.
What is commonly used as an anti-skinning agent in paints?
4.
What is the role of metal naphthenates in paint?
5.
What is the role of turpentine in paint?

From the bank · past-year question

Example 1Industrial and Applied ChemistryHARD

Which one of the following is used as a binder in paints?

[Q65 · Apr · 2019]

Turpentine is the thinner; naphthenates are driers

The bank swaps these in a match-the-pairs question. Turpentine = thinner. Metal naphthenates = drier. Pairing 'drier : turpentine' or 'thinner : naphthenates' is the wrong match.

Binder ≠ pigment

TiO₂ and phthalocyanine are PIGMENTS, not binders. The binder (film-former) is the silicone/resin. When asked for the binder, do not pick a pigment.

Anti-skinning agent = polyhydroxy phenol

Among gelatin, N-methyl pyrrolidone, pyridine and polyhydroxy phenol, the anti-skinning agent is polyhydroxy phenol — the others are solvents/reagents.

Drill 2 more on paint ingredients and their roles

Concept 2 of 2

Emulsion paint additives — true/false facts

Intuition

Emulsion (water-based) paints add a few special agents. The bank tests true/false statements about them: pine oil controls foam, protective colloids INCREASE stability, and oxidizable-oil driers speed drying. Learn which direction each one acts.

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

Practice — Level 1 (3 reps)

Quick reps to lock in the method. Try each, then check.

1.
Pine oil is used as which agent in emulsion paints?
2.
Do protective colloids increase or decrease the stability of emulsion paints?
3.
Why are oxidizable-oil driers added to emulsion paints?

From the bank · past-year question

Example 2Industrial and Applied ChemistryMODERATE

Consider the following statements: I. Pine oil is used as antifoaming agent in emulsion paints. II. Protective colloids are used to decrease stability of emulsion paints. III. Driers having oxidizable oils are added to emulsion paints to accelerate drying. Which are correct?

[Q86 · Apr · 2026]

Protective colloids INCREASE stability

The statement 'protective colloids are used to DECREASE stability of emulsion paints' is false. Protective colloids stabilise the dispersed phase — they increase emulsion 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

Mastery check — 2 interleaved questions

Try each one before clicking. Questions are interleaved across the concepts above, not grouped — interleaving sharpens transfer.

Example 1Industrial and Applied ChemistryHARD

Consider the following pairs: I. Pigment :

\text{TiO}_2

II. Drier : Turpentine III. Thinner : Naphthenates IV. Antiskinning agent : Polyhydroxy phenol How many pairs are correctly matched?

[Q85 · Apr · 2026]

Example 2Industrial and Applied ChemistryHARD

Which one among the following is commonly used as an 'anti-skinning agent' in paints ?

[Q62 · Sep · 2024]

Drill every past-year question on this subtopic

4 questions from the bank — paginated, with cart and Word-export support.

Drill the 4 questions