Drying Time of Paint Films (Cross-reference — IS 101 Part 3 Sec 1)
Drying time — surface-dry (touch/tack-free) and hard-dry (handle/recoat) — is measured per IS 101 Part 3 Section 1 on a conditioned standard panel. Although a different part from the Part 5 hardness method, it is the most-searched IS 101 property because it governs recoat intervals, handling and overpainting on site. It is reported as the time to reach each defined dry state under standard conditions.
Key Requirements
•Use IS 101 Part 3 Section 1 for drying time (this Part 5 page cross-references it because the methods are commonly confused)
•Determine surface-dry (touch/tack-free) and hard-dry (handle/recoat) times on a conditioned standard panel
•Drying time is strongly dependent on film thickness, temperature and humidity — control and report them
•Use the results to set recoat intervals and handling times; judge against the paint product specification
•Do not confuse drying time (Part 3 Sec 1) with film hardness/cure (Part 5 Sec 1) — different methods and meanings
Reference Tables
Drying states (indicative — IS 101 Part 3 Sec 1)
State
Meaning
Governs
Surface dry
Film is touch/tack-free
Dust-free time, handling start
Hard dry
Film withstands handling/pressure
Recoat interval, packing/use
Definitions/limits are in IS 101 Part 3 Sec 1 and the paint product spec — confirm against the current BIS edition.
Practical Notes
✓Drying time is the most practically consequential paint property on site — it sets recoat windows and handling; report it with film thickness and conditions, which strongly affect it.
✓Surface-dry ≠ hard-dry ≠ fully cured: a touch-dry film can still fail handling or recoat — use the correct state for the decision.
Common Mistakes
⚠Citing 'IS 101 drying time' without the part/section — it is specifically Part 3 Section 1.
⚠Reporting drying time without the film thickness and temperature/humidity, which dominate it.
⚠Recoating on surface-dry instead of hard-dry, causing wrinkling/lifting of the previous coat.