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IS 1203:1978 is the Indian Standard (BIS) for methods for testing tar and bitumen: determination of viscosity. This code specifies the empirical method for determining the viscosity of road tars and cutback bitumens using a Standard Tar Viscometer. The viscosity is measured as the time taken in seconds for exactly 50 ml of the bituminous binder to flow through a standard 4 mm or 10 mm orifice at a strictly controlled temperature.
Describes the method for determining the viscosity of cutback and road tars by means of a standard tar viscometer.
Standard Test Method for Kinematic Viscosity of Asphalts (Bitumens)
Directly equivalent to the capillary viscometer portion of IS 1203 for determining kinematic viscosity.
EN 12595:2014CEN (European Committee for Standardization), Europe
HighCurrent
Bitumen and bituminous binders - Determination of kinematic viscosity
European equivalent to the capillary viscometer method in IS 1203, with very similar procedures and apparatus.
EN 12846-1:2012CEN (European Committee for Standardization), Europe
HighCurrent
Bitumen and bituminous binders - Determination of efflux time by the bitumen viscometer - Part 1: Efflux time by the Standard Tar Viscometer
Directly equivalent to the Standard Tar Viscometer (STV) portion of IS 1203.
ASTM D7042-21ASTM International, USA
MediumCurrent
Standard Test Method for Dynamic Viscosity and Density of Liquids by Stabinger Viscometer (and the Calculation of Kinematic Viscosity)
A modern, automated method for determining the same fundamental properties (viscosity) as IS 1203, but using different apparatus.
Key Differences
≠IS 1203 combines two distinct methods (empirical orifice flow and fundamental capillary viscosity) in one standard, whereas international practice typically dedicates separate standards to each method (e.g., EN 12846-1 for orifice and ASTM D2170 for capillary).
≠The Standard Tar Viscometer (STV) method in IS 1203 reports viscosity in empirical units of 'seconds', which is apparatus-dependent. Modern international standards strongly favor fundamental units like Centistokes (mm²/s) from capillary methods.
≠The required temperature control for the thermostatic bath in IS 1203 (±0.1°C) is less stringent than specified in modern international standards like ASTM D2170 (±0.02°C or ±0.05°C depending on temperature), which can affect measurement precision.
≠Being a 1978 standard, IS 1203 lacks the detailed precision and bias statements based on extensive inter-laboratory studies that are mandatory in current ASTM and EN standards.
Key Similarities
≈The fundamental principle of the capillary tube viscometry portion in IS 1203 is identical to that in ASTM D2170 and EN 12595, based on measuring flow time under gravity.
≈All standards use reverse-flow type capillary viscometers (e.g., Cannon-Fenske Opaque, Zeitfuchs Cross-Arm) for opaque liquids like bitumen to ensure the meniscus is visible for timing.
≈The calculation for kinematic viscosity (Viscosity = Calibration Constant × Flow Time) is identical across IS 1203, ASTM D2170, and EN 12595 for the capillary method.
≈Key test temperatures for binder characterization, such as 60°C and 135°C, are common to IS 1203 and its international counterparts for establishing viscosity grades and assessing workability.
Parameter Comparison
Parameter
IS Value
International
Source
Primary Unit (Capillary Method)
Centistokes (cSt)
Centistokes (cSt) or mm²/s
ASTM D2170
Primary Unit (Orifice Method)
Seconds
Seconds
EN 12846-1
Standard Test Temperature (Grading)
60°C
60°C
ASTM D2170
Standard Test Temperature (Mixing/Pumping)
135°C
135°C
ASTM D2170
Orifice Diameter (Standard Tar Viscometer)
10 mm or 4 mm
10 mm or 4 mm
EN 12846-1
Efflux Volume (Standard Tar Viscometer)
50 ml
50 ml
EN 12846-1
Temperature Bath Stability (at 135°C)
± 0.1°C
± 0.05°C
ASTM D2170
Kinematic Viscosity Calculation Formula
ν = C × t
ν = C × t
ASTM D2170
⚠ Verify details from original standards before use
What unit is viscosity expressed in according to IS 1203?+
It is expressed empirically in 'seconds', representing the total time taken for 50 ml of the sample to flow through the viscometer orifice.
What orifice sizes does the standard tar viscometer use?+
It uses standard cups equipped with either a 4 mm or 10 mm diameter orifice, depending on the expected viscosity of the sample.
Is this test suitable for standard paving-grade (penetration) bitumen?+
No, it is generally used for liquid binders like cutback bitumens and road tars. Absolute or kinematic viscosity using capillary tubes (e.g., IS 1206) is used for standard paving bitumens.