IS 101:1988 Part 5/Sec 1 is the Indian Standard (BIS) for methods of sampling and test for paints, varnishes and related products: part 5 chemical tests section 1 volatile matter. This standard prescribes the chemical test method to determine the volatile matter content in paints, varnishes, and related products. Engineers and quality control inspectors use this code to verify the non-volatile (solid) content, assess drying properties, and ensure coatings meet specific quality and environmental specifications.
Specifies methods for determining the volatile matter content of paints, varnishes, and related products.
Key reference values — verify against the current code edition / project specification.
| Reference | Value | Clause |
|---|---|---|
| Subject | Volatile-matter / non-volatile content of paints | Scope |
| Result | % volatile & non-volatile (solids) by mass | Result |
| Why | Solids content drives film build & coverage | Use |
| Method | Controlled heating, mass loss | Method |
| Accept against | The paint product spec (IS 2932/2933 etc.) | Cross-ref |
| VOC link | Volatile content relates to VOC compliance | Note |
IS 101 (Part 5) specifies the methods of sampling and testing for paints, varnishes, and related products — specifically Part 5 deals with mechanical tests on paint films (hardness, flexibility, adhesion, impact resistance, etc.) once the coating has been applied and cured.
IS 101 is a multi-part series — together it forms the standard testing manual for the entire paints/coatings industry in India: - Part 1: Sampling — how to draw representative samples from a batch - Part 2: Tests on liquid paints (consistency, viscosity, density, flow, drying time, hiding power) - Part 3: Tests on paint film formation (drying time, recoatability) - Part 4: Tests on the dry paint film (chemical resistance, water resistance, weathering) - Part 5 (this code): Mechanical tests on dry paint film (hardness, flexibility, adhesion, abrasion, impact) - Subsequent Parts: optical properties, accelerated weathering, etc.
Use IS 101 Part 5 when: - Specifying paint quality acceptance for building work (interior, exterior, anti-corrosive) - Auditing compliance of supplied paint to BIS-marked product standards - Forensic investigation of premature paint failure (peeling, cracking, blistering) - Source qualification of paint manufacturer for large projects - Selecting between competing paint systems (industrial, marine, anti-corrosive, decorative)
Product specifications for individual paint types (e.g., emulsion paint, enamel, anti-corrosive primer, epoxy, polyurethane) cite IS 101 Part 5 method clauses for individual tests. The cosmetic/consumer paint segment is less rigorous; the industrial / structural-protective coatings segment is where IS 101 Part 5 is most enforced.
1. Hardness — Pencil hardness method (Section 2): - Standardised pencils of graded hardness (6B softest → HB → 6H hardest) drawn across the cured paint film at 45° angle, fixed downward force - The hardest pencil that does NOT scratch the film is the film's pencil-hardness rating - Typical values: emulsion paint 2H-3H; enamel 3H-5H; epoxy 5H-7H; polyurethane 6H+
2. Hardness — Sward / König / Persoz pendulum hardness (Section 3): - Damped pendulum oscillations on the paint film; harder film = more oscillations before damping (~30 % amplitude) - Reported as 'Persoz seconds' or 'König seconds' - More precise than pencil for industrial coatings
3. Flexibility / mandrel bend test (Section 4): - Coated panel bent over progressively smaller mandrels (3 mm, 6 mm, 12 mm, 25 mm) - Smallest mandrel diameter at which film does NOT crack = flexibility rating - Acceptance: typical decorative paint passes 12 mm mandrel; flexible epoxy / elastomeric passes 3 mm
4. Adhesion — Cross-cut tape test (Section 5): - Cross-hatch grid (6 horizontal × 6 vertical cuts at 1 mm or 2 mm spacing) cut through paint film with sharp blade - Adhesive tape applied firmly over grid, then peeled off at constant rate - Rating from 0 (no peel — perfect adhesion) to 5 (>65 % peel — gross failure) - Acceptance: ≤ Grade 1 for decorative; Grade 0 for protective / industrial
5. Adhesion — Pull-off test (Section 6): - Dolly (cylindrical pin) glued to the paint film with epoxy adhesive - Tensile force applied perpendicular to film via portable adhesion tester - Force at failure / dolly area = pull-off adhesion strength (MPa) - Acceptance: typical 2-5 MPa for industrial coatings; ≥ 1 MPa for decorative
6. Impact resistance (Section 7): - Steel ball (or weighted impactor) dropped from prescribed height onto coated panel - Direct impact (back-side) and reverse impact (face-side) tested - Acceptance: no cracking / spalling at specified impact energy (e.g., 1 N⋅m)
7. Abrasion resistance (Section 8): - Falling-sand abrasion test (sand poured from height onto coated panel, mass of sand to expose substrate) - Or rotating-wheel (Taber) abrasion test (cycles to thickness loss) - Important for floor coatings, exterior weathering paint
8. Resistance to indentation (Section 9): - Hardness measurement under static load (Buchholz indenter) - Width of indent = hardness rating
Interior emulsion paint (IS 5411 Part 1:1974): - Pencil hardness: ≥ 2H - Cross-cut adhesion: Grade 1 max - Flexibility: passes 25 mm mandrel - Drying time (touch dry): ≤ 30 min - Recoat time: 4 hr
Exterior acrylic paint (IS 15489:2013): - Pencil hardness: ≥ 3H - Cross-cut adhesion: Grade 0 - Flexibility: passes 12 mm mandrel - UV resistance: pass per accelerated weathering test (Part 4 ref) - Water resistance: no blistering after 100 hr immersion
Anti-corrosive primer (red oxide / zinc-rich, IS 102:1962): - Pencil hardness: ≥ 2H after 7 days curing - Cross-cut adhesion: Grade 0 (perfect) - Pull-off adhesion: ≥ 2 MPa - Salt spray test (IS 6005): no rust at 250 hr - Impact resistance: pass at 1 N⋅m direct
Epoxy floor coating (industrial): - Pencil hardness: ≥ 5H - Pull-off adhesion: ≥ 4 MPa on concrete substrate - Abrasion (Taber CS-17 wheel, 1000 cycles): mass loss ≤ 100 mg - Chemical resistance: no softening after 24 hr in dilute acid / oil / solvent
Polyurethane top coat (anti-corrosive system): - Pencil hardness: ≥ 6H - Pull-off adhesion: ≥ 3 MPa on epoxy primer - UV gloss retention: ≥ 80 % after 1000 hr accelerated weathering - Impact resistance: pass at 2 N⋅m direct
Pencil hardness scale (for reference): - 6B (softest) → 5B → 4B → 3B → 2B → B → HB → F → H → 2H → 3H → 4H → 5H → 6H → 7H → 8H → 9H (hardest)
1. Acceptance test on freshly-applied paint. Cure time matters — pencil hardness on day-1 paint reads soft; on day-7 it's at design value. Always test after the supplier's specified curing time (typically 7 days for emulsion, 14-21 days for epoxy/PU). 2. Cross-cut adhesion on poorly-prepared substrate. The test reveals adhesion of the coating to the substrate. If the substrate has dust, oil, or loose laitance, the failure is at the substrate, not within the coating system — but the test fails. Always verify surface preparation per coating supplier datasheet. 3. Mandrel test on rigid panel. The test is for plate-coatings (exterior cladding, vehicle bodies). Doesn't apply to wall paint on rigid masonry. 4. Pull-off test using the wrong adhesive. The dolly-to-coating bond must be stronger than the coating-to-substrate bond. If the dolly adhesive (epoxy) fails first, the test is invalid. Use slow-cure structural epoxy (24 hr cure). 5. Single test result without averaging. Coating thickness varies; a single pull-off can hit a thin spot. Run 5-6 dolly tests per panel; report mean and CV. 6. Acceptance criterion not in the BOQ. Buyer specifies 'epoxy floor coating' but doesn't say what hardness or adhesion to test against. Always cite the IS 101 Part 5 Section + the acceptance value (e.g., `pencil hardness ≥ 5H per IS 101 Part 5 Section 2`). 7. Pencil hardness measured by inspector with worn pencils. Lead degrades; values drift. Use freshly-sharpened pencils for every test, or use Persoz/König pendulum for industrial-grade testing. 8. Adhesion test ignoring environmental factor. Coatings tested in dry season look perfect; in monsoon humidity, water-sensitive coatings fail. For exterior / wet exposure, condition specimens at high humidity (24 hr at 95 % RH) before testing. 9. Confusing flexibility with flex-fatigue. Mandrel bend tests static flexibility (one bend). Cyclic flex (e.g., for painted metal facade panels under wind load) requires fatigue testing — different test entirely. 10. Source qualification only — no batch checking. Even ISI-marked paints have batch-to-batch variation in pigment loading and rheology. For large jobs, sample test from each batch as it arrives at site.
Standard cascade for a structural / protective coating system:
1. Substrate identification — concrete, steel, masonry, plaster, wood — each has its own primer requirement. 2. Surface preparation — cleaning, derusting (Sa 2.5 blast clean for steel per IS 9954), degreasing, profile measurement. 3. Coating system specification — primer + intermediate + topcoat; total dry-film thickness (DFT) target. 4. Procurement — ISI-marked product per relevant product spec; supplier datasheet + IS 101 Part 5 test certificate from NABL lab for source qualification. 5. Application — brush / roller / spray; environmental conditions (dust-free, RH < 80 %, surface temp 5 °C above dew point); per-coat DFT measured by dry-film gauge. 6. Curing — per supplier datasheet; environmental control during cure. 7. Acceptance testing: - DFT measurement at random points (≥ 10 per area) - Adhesion (cross-cut or pull-off) at random points (≥ 3 per area) - Pencil hardness verification - Visual: gloss, colour, run/sag, holiday detection 8. Documentation: as-applied report, batch numbers, application date, environmental conditions, test results. 9. Maintenance regime — cleaning frequency, repaint intervals (typically 5-10 years for exterior; 10-20 for industrial protective).
IS 101 Part 5 enters at step 4 (source qualification) and step 7 (acceptance). For large industrial / marine projects, third-party NABL lab testing per IS 101 Part 5 is standard practice; for residential / small commercial, manufacturer's BIS-licence + ISI mark + datasheet are the practical baseline.