ISO 15715:2025
(Main)Binders for paints and varnishes — Determination of turbidity
Binders for paints and varnishes — Determination of turbidity
This document specifies an instrumental method for determining the turbidity of clear liquids. It is applicable to resins and resin solutions, solvents, clear coating materials, monomers and any other liquids where clarity is specified.
Liants pour peintures et vernis — Détermination de la turbidité
L'ISO 15715:2003 spécifie une méthode instrumentale pour la détermination de la turbidité de liquides clairs. Elle s'applique aux résines et aux solutions de résine, aux solvants, aux revêtements transparents, aux monomères et à tout autre liquide dont la transparence est spécifiée.
General Information
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Standards Content (Sample)
International
Standard
ISO 15715
Second edition
Binders for paints and varnishes —
2025-06
Determination of turbidity
Liants pour peintures et vernis — Détermination de la turbidité
Reference number
© ISO 2025
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Published in Switzerland
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
4.1 Principle of the method .1
4.2 General principles of turbidity measurement .1
5 Apparatus . 2
5.1 Turbidimeter.2
5.2 Measurement cells . . .3
6 Calibration . 3
7 Procedure . 3
8 Expression of results . 4
9 Precision . 4
10 Test report . 4
Annex A (normative) Preparation of formazin standards . 5
Annex B (informative) Use of additional measurement angles . 6
Bibliography . 7
iii
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
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with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
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This document was prepared by Technical Committee ISO/TC 35, Paints and varnishes, in collaboration with
the European Committee for Standardization (CEN) Technical Committee CEN/TC 139, Paints and varnishes,
in accordance with the Agreement on technical cooperation between ISO and CEN (Vienna Agreement).
This second edition cancels and replaces the first edition (ISO 15715:2003), which has been technically
revised.
The main changes are as follows:
— Clause 2 has been added;
— the principle (new 4.1) has been amended by a description of influences which can affect turbidity
measurements;
— formazin turbidity units (FTU) has been changed to formazin nephelometric units (FNU), to be in line
with ISO 7027-1:2016;
— the optical path length of the tube has been changed in 5.2;
— in Clause 6, a reference to commercially available calibration standards has been added as well as a
reference to room temperature for storing the calibration standards;
— a reference to ISO 7027-1 has been added for precision;
— the expression of results in Clause 8 has been reduced to three classes, i.e. the former classes 10 FNU to
less than 100 FNU and greater or equal to 100 FNU have been combined to one class, to report the result
to the nearest 1 FNU;
— the normative references have been updated.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv
Introduction
The measurement of the turbidity of liquids can be carried out visually or using an instrument, but visual
methods can be subjective. This method instrumentally measures the scattering of light by the insoluble
matter in a liquid and therefore gives an objective determination of turbidity.
Turbidity in liquids is caused by the presence of undissolved matter (i.e. non-settling flocculation, gels or
other suspended matter such as particles or droplets). In the case of finely dispersed undissolved matter, the
turbidity can be determined by measuring the intensity of the light which is scattered by the particles when
a beam of light is passed through the liquid.
v
International Standard ISO 15715:2025(en)
Binders for paints and varnishes — Determination of
turbidity
1 Scope
This document specifies an instrumental method for determining the turbidity of clear liquids. It is
applicable to resins and resin solutions, solvents, clear coating materials, monomers and any other liquids
where clarity is specified.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 4618, Paints and varnishe
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