EN 16128:2025
(Main)Ophthalmic optics - Reference method for the testing of spectacle frames and sunglasses for nickel release
Ophthalmic optics - Reference method for the testing of spectacle frames and sunglasses for nickel release
This document specifies the reference method for the testing of spectacle frames, ready-to-wear near-vision spectacles, sunglasses and spectacle frames used for eye and face protection for nickel release.
The reference method supports the demonstration of conformity with the limit value for nickel release of 0,5 µg·cm−2·week−1 set forth by European Regulation.
The reference method involves the procedural steps shown in Figure 1 and described in Clause 4.
This document applies to those parts of metal spectacle frames and those metal parts of combination spectacle frames that are intended to come into direct and prolonged contact with the skin of the wearer. This document also applies to those relevant metal parts of ready-to-wear near-vision spectacles, sunglasses and spectacle frames used for eye and face protection.
NOTE The reference method for articles apart from spectacle frames, ready-to-wear near-vision spectacles, sunglasses and spectacle frames used for eye and face protection is specified in EN 1811.
Augenoptik - Referenzverfahren für die Bestimmung der Nickellässigkeit von Brillenfassungen und Sonnenbrillen
Dieses Dokument legt das Referenzverfahren für die Prüfung der Nickellässigkeit von Brillenfassungen, Nah-Fertigbrillen, Sonnenbrillen sowie Brillenfassungen fest, die als Augen- und Gesichtsschutz angewendet werden.
Das Referenzverfahren unterstützt den Nachweis der Einhaltung des in der Europäischen Verordnung festgelegten Grenzwerts für die Nickellässigkeit von 0,5 µg·cm−2·Woche−1.
Das Referenzverfahren umfasst die in Bild 1 dargestellten und in Abschnitt 4 beschriebenen Verfahrensschritte.
Dieses Dokument gilt für diejenigen Teile von Metall-Brillenfassungen sowie diejenigen Metallteile von Kombinations-Brillenfassungen, die bestimmungsgemäß in direkten und länger dauernden Kontakt mit der Haut des Trägers kommen. Dieses Dokument gilt ebenfalls für die entsprechenden Metallteile von Nah-Fertigbrillen, Sonnenbrillen sowie Brillenfassungen zum Augen- und Gesichtsschutz.
ANMERKUNG Das Referenzverfahren für alle Produkte mit Ausnahme von Brillenfassungen, Nah-Fertigbrillen, Sonnenbrillen und Brillenfassungen zum Augen- und Gesichtsschutz ist in EN 1811 festgelegt.
Optique ophtalmique - Méthode d’essai de référence relative à la libération du nickel par les montures de lunettes et les lunettes de soleil
Le présent document spécifie la méthode d’essai de référence pour la libération du nickel par les montures de lunettes, les lunettes prémontées pour vision de près, les lunettes de soleil et les montures de lunettes utilisées pour la protection des yeux et du visage.
La méthode de référence soutient la démonstration de la conformité avec la valeur limite de libération du nickel de 0,5 µg·cm−2·semaine−1 fixée par le Règlement européen.
La méthode de référence implique les étapes de mode opératoire présentées sur la Figure 1 et décrites à l’Article 4.
Le présent document s’applique aux parties des montures de lunettes en métal et aux parties en métal des montures de lunettes combinées destinées à venir en contact direct et prolongé avec la peau du porteur. Il s’applique également aux parties en métal pertinentes des articles pour les lunettes prémontées pour vision de près, les lunettes de soleil et les montures de lunettes utilisées pour la protection des yeux et du visage.
NOTE La méthode de référence pour les articles autres que les montures de lunettes, les lunettes prémontées pour vision de près, les lunettes de soleil et les montures de lunettes utilisées pour la protection des yeux et du visage, est spécifiée dans l’EN 1811.
Očesna optika - Referenčna preskusna metoda za ugotavljanje sproščanja niklja iz okvirjev očal in sončnih očal
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
01-december-2025
Nadomešča:
SIST EN 16128:2016
Očesna optika - Referenčna preskusna metoda za ugotavljanje sproščanja niklja iz
okvirjev očal in sončnih očal
Ophthalmic optics - Reference method for the testing of spectacle frames and
sunglasses for nickel release
Augenoptik - Referenzverfahren für die Bestimmung der Nickellässigkeit von
Brillenfassungen und Sonnenbrillen
Optique ophtalmique - Méthode d'essai de référence relative à la libération du nickel par
les montures de lunettes et les lunettes de soleil
Ta slovenski standard je istoveten z: EN 16128:2025
ICS:
11.040.70 Oftalmološka oprema Ophthalmic equipment
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
EN 16128
EUROPEAN STANDARD
NORME EUROPÉENNE
October 2025
EUROPÄISCHE NORM
ICS 11.040.70 Supersedes EN 16128:2015
English Version
Ophthalmic optics - Reference method for the testing of
spectacle frames and sunglasses for nickel release
Optique ophtalmique - Méthode d'essai de référence Augenoptik - Referenzverfahren für die Bestimmung
relative à la libération du nickel par les montures de der Nickellässigkeit von Brillenfassungen und
lunettes et les lunettes de soleil Sonnenbrillen
This European Standard was approved by CEN on 8 September 2025.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2025 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 16128:2025 E
worldwide for CEN national Members.
Contents Page
European foreword . 4
Introduction . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 7
4 Principle . 8
5 Selection of test samples . 9
6 Simulation of wear and corrosion . 10
6.1 Preparation of test samples . 10
6.2 Procedure. 11
7 Coating test . 11
7.1 General . 11
7.2 Apparatus and consumables . 12
7.3 Preparation of test samples for the coating test . 13
7.3.1 Parts to be tested . 13
7.3.2 Dismantling and/or cutting and/or masking . 13
7.3.3 Determination of test area . 15
7.3.4 Preparation of electrical contact area . 15
7.4 Preparation of saline solution . 15
7.5 Procedure. 15
7.5.1 Preparation of the electro-chemical cell . 15
7.5.2 Insertion and connection of the test part in the electro-chemical cell . 16
7.5.3 Determination of open circuit potential and measurement of electrochemical impedance
of test samples . 16
7.5.4 Calibration and verification of the equipment . 17
7.6 Calculation of results . 17
7.6.1 General . 17
7.6.2 Criteria for pass or fail of the test sample . 17
7.7 Test report . 17
8 Release of nickel and its quantitative analytical detection (migration test) . 19
8.1 General . 19
8.2 Apparatus and consumables . 19
8.3 Preparation of test samples for the migration test . 21
8.3.1 Parts to be tested – general . 21
8.3.2 Small parts to be tested . 21
8.3.3 Guidance on selection of test areas on the parts to be tested . 21
8.3.4 Dismantling and degreasing . 22
8.4 Procedure. 22
8.4.1 Preparation of test paper including determination of its area . 22
8.4.2 Preparation of artificial sweat solution . 23
8.4.3 Applying artificial sweat solution to the test paper and attaching it to the test sample . 24
8.4.4 Blank sample . 25
8.4.5 Incubation of test sample with test paper attached (release of nickel into paper) . 25
8.4.6 Retrieval of the test paper from the test samples . 25
8.4.7 Analysis of the test papers for nickel . 26
8.5 Calculation of migration test results . 27
8.6 Interpretation of migration test results . 28
8.6.1 General . 28
8.6.2 Assessment of compliance . 28
8.6.3 Retesting after a fail result with the migration test . 29
8.7 Test report . 29
Annex A (informative) Examples of mounting test samples in the EN 12472 tumbling barrel. 31
Annex B (normative) Measuring device and identifying where to test sides . 32
Annex C (informative) Cutting and masking of test samples (Coating test) . 38
Annex D (informative) Quality control material for the coating test . 42
Annex E (normative) Selection of test areas and application of the test paper (Migration test) . 43
Bibliography . 49
European foreword
This document (EN 16128:2025) has been prepared by Technical Committee CEN/TC 170 “Ophthalmic
optics”, the secretariat of which is held by DIN.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by April 2026, and conflicting national standards shall be
withdrawn at the latest by April 2026.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN 16128:2015.
— Clause 4 has been modified to give a better scientific explanation of why a sample that fails the
coating test might pass the migration test. It also states that the coating test is not a screening test
since a pass allows a product to be labelled as compliant with REACH. A revised flowchart (Figure 1)
reinforces this. The warning about taking particular attention over handling samples to avoid
additional damage has been reinforced;
— Clause 5 emphasizes that if a sample fails the coating test, then all parts of the sample have to be
tested with the migration test, not just the part that failed;
— Clause 6 notes that the lenses are needed in the frame to protect the groove during the simulated
wear and corrosion procedure. Although it applies to EN 12472, new Annex A provides illustrations
of mounts that can be used to hold sample frames in the tumbling barrel;
— Clauses 7 and 8 refer to the new normative Annex B for advice on where to test sides. Both
recommend that the test or dummy lenses are kept in the frame for the tests;
— More detailed advice on where to mask frames before the coating test has been provided in Clause 7.
The new quality control samples are mentioned in the new Annex D. Photographic records of the
samples are now required in the test report;
— Clause 8 now permits the use of a hermetically-sealed cabinet and laboratory oven to be used for the
migration process as well as a climate chamber. The concentration of the control solution has been
doubled and the volume halved, to avoid overloading the piece of test paper, which is suggested to
be 10 % larger. Again, photographic records of the samples are now required in the test report;
— Annexes B, C and D have photographic figures to illustrate sample preparation since they give better
clarity than drawings. The examples pictured provide no manufacturer markings and are in no way
intended to promote a particular manufacturer or style;
— Annex E has been revised to recommend folding of the sealing film over the test or dummy lenses
rather than wrapping around the rim.
This document has been prepared under a standardization request addressed to CEN by the European
Commission. The Standing Committee of the EFTA States subsequently approves these requests for its
Member States.
Any feedback and questions on this document should be directed to the users’ national standards body.
A complete listing of these bodies can be found on the CEN website.
According to the CEN-CENELEC Internal Regulations, the national standards organisations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia,
Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland,
Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of North
Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the United
Kingdom.
Introduction
This document has been prepared under Mandate M/448 issued by the European Commission in the
framework of Regulation (EC) No 1907/2006, REACH, in particular Commission Regulation
(EC) No 552/2009 of 22 June 2009 amending regulation (EC) No 1907/2006 of the European Parliament
and of the Council on the Registration, Evaluation, Authorization and restriction of Chemicals (REACH)
as regards Annex XVII RESTRICTIONS ON THE MANUFACTURE, PLACING ON THE MARKET AND USE OF
CERTAIN DANGEROUS SUBSTANCES, PREPARATIONS AND ARTICLES.
The aim of the mandate was the development of a new method of analysis to detect the release of nickel
from spectacle frames and sunglasses.
The availability of the new reference method for the determination of the release of nickel will provide
the reliable framework to enforce the limit value for nickel release set forth by the European Regulation
−2 −1 2
of 0,5 μg·cm ·week (expressed as 0,5 µg/cm /week in the Regulation). It will ensure a uniform
application and control of the European legislation in all member states.
Harmonizing the test method for nickel release in all member states is vital with a view to protecting
effectively the health of the end consumer, that is, the spectacle wearer. Nickel allergy is still the most
frequent contact allergy in Europe and a significant health issue.
1 Scope
This document specifies the reference method for the testing of spectacle frames, ready-to-wear near-
vision spectacles, sunglasses and spectacle frames used for eye and face protection for nickel release.
The reference method supports the demonstration of conformity with the limit value for nickel release
−2 −1
of 0,5 µg·cm ·week set forth by European Regulation.
The reference method involves the procedural steps shown in Figure 1 and described in Clause 4.
This document applies to those parts of metal spectacle frames and those metal parts of combination
spectacle frames that are intended to come into direct and prolonged contact with the skin of the wearer.
This document also applies to those relevant metal parts of ready-to-wear near-vision spectacles,
sunglasses and spectacle frames used for eye and face protection.
NOTE The reference method for articles apart from spectacle frames, ready-to-wear near-vision spectacles,
sunglasses and spectacle frames used for eye and face protection is specified in EN 1811.
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.
EN 12472, Method for the simulation of accelerated wear and corrosion for the detection of nickel release
from coated items
EN ISO 3696, Water for analytical laboratory use — Specification and test methods (ISO 3696)
EN ISO 7998:2005, Ophthalmic optics — Spectacle frames — Lists of equivalent terms and vocabulary
(ISO 7998:2005)
EN ISO 12870:2025, Ophthalmic optics — Spectacle frames — Requirements and test methods
(ISO 12870:2024)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in EN ISO 12870:2025,
EN ISO 7998:2005 and the following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https://www.iso.org/obp/
— IEC Electropedia: available at https://www.electropedia.org/
3.1
model
spectacle frame, ready-to-wear spectacles, sunglass or other item used for eye and face protection
produced to the same design, using the same materials and surface treatment, and to which the scope of
this document applies
3.2
test sample
spectacle frame, ready-to-wear spectacles, sunglass or other item used for eye and face protection
submitted for testing
3.3
test part
part of a test sample that is intended to come into direct and prolonged contact with the skin and
therefore requires testing
Note 1 to entry: These parts are defined in 7.3.1 (for the coating test) and in 8.3.1 (for the migration test).
3.4
test paper
piece of laboratory cellulose paper used for testing, at any stage of the procedure after being cut to size
for testing
3.5
extraction solution
solution obtained after extraction of nickel ions from the test paper
3.6
appropriate tool
tool enabling the procedure to be performed without causing contamination by nickel or other metal ions,
either from the material of the tool or deposits on it
Note 1 to entry: Such tools could be made from plastics, titanium, or stainless steels.
3.7
appropriate equipment
equipment enabling the procedure to be performed without causing contamination by nickel or other
metal ions, either from the material of the equipment or deposits on it
3.8
electrically non-conductive coated part
part of a test sample that has a covering, on a substrate, that does not conduct an electrical current and
has protective and/or decorative properties
Note 1 to entry: These non-conductive coatings/coverings are generally based on organic polymers.
4 Principle
Following the simulation of wear and corrosion according to the method specified in EN 12472 (see
Clause 6), the reference method comprises the following two tests:
1) Coating test, applicable only to test parts with an electrically non-conductive coating, based on
Electrochemical Impedance Spectroscopy (EIS) and specified in Clause 7. Its aim is to demonstrate
the ability of the electrically non-conductive coating to limit any release of metal ions from the test
sample substrate as indicated by the impedance threshold, thereby ensuring that the nickel release
from the test sample does not exceed the regulatory limit. The coating test is a test of the ability of
the electrically non-conductive coating to prevent the release of metal ions from the substrate of the
test sample. A pass in this test can be used to claim compliance with REACH.
2) Migration test for nickel ion release, specified in Clause 8, is a quantitative test to determine whether
or not the nickel release from the model exceeds the regulatory limit. The migration test comprises
two steps: Release of nickel by artificial sweat solution into a test paper and the subsequent
quantitative analytical detection of the nickel released into the paper.
Figure 1 illustrates the relationship between the two tests; the coating test is not a screening test since a
pass allows a product to be labelled as compliant with REACH. In addition to frames without an
electrically non-conductive coating, the coating test cannot be applied to the following for technical
reasons: very small components (e.g. screw heads, trims on sides, side tips or fronts – see 8.3.2) and
frames fitted with magnets (e.g. to hold clip-ons).
Metal frames that are uncoated (i.e. neither organic coated nor metal plated) and made of homogeneous
alloys or metals do not require the simulation of wear and corrosion specified in Clause 6 and shall be
tested directly in accordance with Clause 8. Unless the manufacturer certifies that a component is
homogeneous and uncoated, the component shall be assumed to be coated.
If a part of the sample fails the coating test, that part of the same test sample can be retested with the
coating test (7.5.3).
In general, it is recommended that all suitable frames should be tested with the coating test, and only
those that are unsuitable or fail the coating test be subject to the migration test. The laboratory's client
is, however, not restrained from preferring to test frames directly with the migration test, provided the
request is provided in writing to the laboratory.
If a sample fails the coating test and the laboratory's client wishes to proceed further with testing, either
new test samples or, subject to the requirements of the laboratory's client, the original test samples shall
be subjected to the migration test in order to verify whether nickel ions are subsequently released and to
obtain a quantitative value. For example, a thin coating on a substrate (such as a titanium alloy) that does
not release nickel might fail the coating test but pass the migration test.
Requirements for sampling and guidance as to which parts of the test samples shall be subject to testing
(the test parts) are given in Clause 5 and in 7.3.1 (for the coating test) and 8.3.1 (for the migration test).
WARNING — Test laboratories shall pay particular attention to the careful handling of test samples and
test parts during all stages of this standard, using appropriate tools when needed. Poor handling,
particularly when dismantling or cutting a test sample, may cause additional damage that causes a failure.
5 Selection of test samples
The laboratory's client should select, at random, two representative specimens of each model to be tested
for either the coating or the migration test.
The selected specimens shall be labelled, e.g. by allocating them a laboratory code or number for
identification.
Test samples used for the coating test can be tested in a subsequent migration test, but test samples used
for the migration test cannot be tested in a subsequent coating test.
If a test sample is likely to be subjected to the migration test after the coating test, it shall be washed
thoroughly in deionized water immediately after the coating test and allowed to dry to avoid corrosion
from sodium chloride.
Key
a The coating test is a test of the ability of the electrically non-conductive coating to prevent the release of
metal ions from the substrate of the test sample. If a sample fails the coating test and the laboratory's
client wishes to proceed further with testing, the samples or new samples shall be subjected to the
migration test in order to verify whether nickel ions are subsequently released and to obtain a
quantitative value. See Clause 4.
b On the request of the laboratory's client, test samples can be tested directly using the migration test, but the
extra information about the coating that is obtained by using the coating test will be unknown.
c The coating test cannot be used to test very small components, e.g. screw heads, trims on sides, side tips or
fronts. It also cannot be used with frames fitted with magnets, e.g. to hold clip-ons.
If a sample fails, conductivity of parts not in contact with the skin (for example, trims) shall be verified using
an electric circuit tester and shall be masked if uncoated.
Figure 1 — Diagrammatic overview of the reference test method
6 Simulation of wear and corrosion
6.1 Preparation of test samples
Samples should be fitted with test lenses, which should preferably be supplied or specified by the
laboratory's client, i.e. the manufacturer or importer or authorized representative.
NOTE 1 The lenses protect the edges of the groove, so that testing without lenses can cause a false failure.
If the client agrees, then the dummy or demonstration lenses can be used.
NOTE 2 The greater thickness of organic prescription spectacle lenses can give superior protection to the edge
of the groove than a dummy or demonstration lens.
If test lenses are not supplied or specified, then the testing laboratory shall contact the frame
manufacturer for a recommendation for the test lens's material, power, thickness, curvature and, as
appropriate, bevel angle or edge profile.
In the absence of supply or specifications from the manufacturer or an inability to contact the
manufacturer, test lenses are recommended to be of suitable material for the type of frame and have a
vertex power of (0,00 ± 0,25) D, a centre thickness of (2,00 ± 0,20) mm and a curvature appropriate for
the frame.
For all test samples, sides and fronts shall be separated from each other. Sides shall be dismantled from
fronts, either by unscrewing the dowel (hinge) screw or by cutting the joint across the charniers (leaves
of the hinge).
Unless they have a metal-bearing surface, nose pads shall be removed. To avoid subsequent difficulties
with masking the pad box for the coating test, it is recommended that, except for frames fitted with pads
having a metal-bearing surface, the pads be removed by cutting off the pad arms complete with the pad
box and pads, see 7.3.2.
Removing end covers (side tips) from sides is optional.
Ensure that all the separate test parts remain identified throughout all steps of the overall procedure.
6.2 Procedure
Except for components that are certified by the manufacturer to be homogenous and uncoated, perform
the simulation of wear and corrosion according to EN 12472. Ensure that the paste is not used after its
shelf life has expired.
NOTE Fronts can conveniently be clamped by means of the dummy or test lenses, and sides on the part that is
covered by the end cover (temple tip). See Annex A. EN 12472 specifies that the back surface of the front and inside
of the sides face towards the axis of the assembly.
When the simulation is completed, remove the test samples. Gently swirl them for 2 min in degreasing
solution (see 7.2.4) at room temperature. Rinse thoroughly with deionized water. Gently dry in a clean
air stream or allow to dry on absorbent paper.
After degreasing, handle the test samples with appropriate tools or clean laboratory gloves.
Disassemble three-piece rimless fronts. Disassemble fronts of combination frames and remove any
plastic parts.
Then subject the test parts to the selected test: coating test, see Clause 7, and/or migration test, see
Clause 8.
7 Coating test
7.1 General
The purpose of the coating test is to verify whether the surface treatment of a model is able to limit
sufficiently the release of metal ions (including nickel), as indicated by the impedance threshold limit.
Test samples that are not identified as “pass” can be retested if 7.5.3 applies or be subjected to the
migration test, see Clauses 4 and 5.
The parts of test samples needing consideration are only those intended to come into direct and
prolonged contact with the skin of the wearer, see 7.3.1.
7.2 Apparatus and consumables
7.2.1 Masking agent, suitable for electroplating purposes and capable of electrically insulating the test
part from the saline solution. Application of more than one coat is acceptable and can be preferable.
Test the masking agent to verify that it is suitable by using it to coat a metal strip without an organic
coating and show that the adhesion is good and impedance results are high (greater than
6 2
5,0 ⋅ 10 Ω ⋅ cm ).
NOTE 1 A metal strip with approximate dimensions of 2 mm thick, 6 mm wide, and 100 mm long is suitable.
It is useful if the masking agent is coloured or fluorescent, to make the masked areas more visible.
1)
NOTE 2 Lacomit is the trade name of a suitable product.
7.2.2 Deionized water, according to EN ISO 3696, grade 3 or to European Pharmacopoeia, for rinsing
and preparation of the saline solution (7.4).
7.2.3 Sodium chloride of recognized pro analysis, p.a. grade or better, for preparation of the saline
solution (7.4).
7.2.4 Degreasing solution, to clean the test samples after cutting, etc. and before testing. Dissolve 5 g
of an anionic surface-active agent such as sodium dodecylbenzene sulfate or sodium alkylaryl sulfate in
1 000 ml deionized water (7.2.2). An appropriately diluted, neutral, commercially available detergent can
also be used.
7.2.5 Apparatus for preparation of 1 % saline solution in deionized water.
7.2.6 Electro-chemical cell, made of glass, suitable for mounting firstly a Standard Calomel (SCE) or
Ag/AgCl Reference Electrode, secondly a Graphite or Platinum Counter Electrode and thirdly, the test
part.
The recommended counter electrode is a high-density pure graphite rod, approximately 6 mm in
diameter.
7.2.7 Laboratory clamps, suitable for holding the test part, with the selected area immersed in the
electrolyte in the electro-chemical cell, but with the electrical contact area kept dry.
7.2.8 Potentiostat, having the ability to perform A.C. Electrochemical Impedance Spectroscopy (EIS)
at 1 Hz and having a current sensitivity of better than 1 pA.
2)
NOTE An example of suitable apparatus is Gamry apparatus Interface 1010B package.
7.2.9 Electrical clamps, e.g. small crocodile clips, capable of providing secure electrical contact with
the test part, reference and counter electrodes.
7.2.10 Calibration (dummy) cell, usually supplied by the potentiostat manufacturer together with the
instrument, appropriate to test the potentiostat in the impedance range expected.
1)
Lacomit is an example of a suitable product available commercially. This information is given for the convenience
of users of this document and does not constitute an endorsement by CEN of this product. Equivalent products can
be used if they can be shown to lead to the same results.
2)
Gamry apparatus Interface 1010B is an example of a suitable product available commercially. This information is
given for the convenience of users of this document and does not constitute an endorsement by CEN of this product.
7.2.11 Appropriate tools, needed to perform the procedure. See 3.6 for the definition of “appropriate
tools”. To prevent possible contamination by nickel or other metal ions, clean all tools well before and
after use.
7.2.12 Laboratory gloves, e.g. latex or PVC, but not cotton.
7.2.13 Faraday cage; either an earthed Faraday cage, earthed aluminium foil or earthed conductive
cloth to house the electro-chemical cell during measurement.
7.3 Preparation of test samples for the coating test
7.3.1 Parts to be tested
See Clause 5 for sampling requirements.
For testing of models with the coating test, the parts to be tested are:
a) the front, comprising the rims, the bridge and, if applicable, the brace bar but excluding the pad arms
and pad boxes, lugs and, if temporal, closing block joints;
b) sides (temples), including metal collets, but excluding those areas intended to be protected by plastic
end covers (tips). Joints and the zone immediately around them are excluded unless they are in the
zone to be tested. Sides shall be tested in the areas specified in Annex B.
Nose pads with metal-bearing surfaces shall be tested using the migration method in Clause 8.
For each of the two test samples, the front and the two sides shall be tested separately; all three parts of
both test samples shall pass in order for the model to pass.
7.3.2 Dismantling and/or cutting and/or masking
7.3.2.1 General
Prior to submission to the coating test, the test sample shall have been subject to the method for
simulation of wear and corrosion according to EN 12472. See Clause 6.
After completion of the simulation of wear and corrosion, select and separate those parts (or areas) that
are subject to the coating test from those that are not. This can be achieved by one or more of the
following:
a) dismantling (see 7.3.2.2);
b) cutting (see Annex C);
c) masking (see 7.3.2.3 and Annex C).
The dummy or test lenses needed for the simulation of wear and corrosion (see 6.1) shall be left in the
front.
NOTE 1 Removing dummy or demonstration lenses by pushing them out without opening the closing block (lens
retaining) joint risks damaging the coating on the inside of the rims.
Consider the need for preparing the electrical contact area (see 7.3.4) and for determination of surface
area (see 7.3.3) when deciding where to cut or which areas to mask. Masking any “complicated” details
of the test sample that would not come into direct and prolonged contact with the skin could simplify the
determination of surface area and/or enhance its precision.
Cutting of the test samples except across the charniers and pad arms (see 6.1), to separate the parts (or
areas) to be tested from those not to be tested, is permissible but should be avoided if at all possible.
NOTE 2 Cutting can be avoided by masking the entire test part except those parts (or areas) to be subjected to
the test.
CAUTION — If cutting is undertaken, great care shall be taken to avoid contamination by metal ions e.g.:
— from the base material;
— from metal particles getting underneath the masking;
— by damaging the organic coating that is near the cut and subsequently tested;
— from metal on tools or fingers or the work area.
Ensure that all the separate parts of the test samples remain identified, e.g. assign identification numbers
or codes, while not physically touching or modifying them.
7.3.2.2 Dismantling
Nose pads with metal-bearing surfaces shall be dismantled from fronts as they need to be tested
according to Clause 8.
7.3.2.3 Masking
Gently swirl the test sample(s) for 2 min in degreasing solution (7.2.4) at room temperature. Rinse
thoroughly and carefully with deionized water (7.2.2) and gently dry in a clean air stream or allow to dry
on absorbent paper.
NOTE This cleaning stage is intended to remove plasticizers from packaging, extraneous grease and skin
secretions due to handling, but not any protective coatings.
After degreasing, handle the test samples with appropriate tools or clean laboratory gloves.
3)
Masking can be done by dipping, using a dispenser with a syringe having a fine needle or painting, either
with a brush or with a dental plugger. Whichever method is used, ensure that the resulting masking film
is much thicker than, e.g. twice as thick as, the original coating of the test sample or the part thereof.
Ensure that cut edges are covered. Dip or paint/brush twice, allowing approximately 30 min between the
applications. After allowing the masking agent to dry for a minimum of 15 min, inspect the quality of
masking visually with a low-powered (e.g. 2x to 5x) magnifier to ensure complete coverage of the
appropriate areas. If required, apply an additional layer(s) of masking agent. See Annex C for details.
Closing blocks, if temporal, including their screws shall be masked, if intended to be immersed. Closing
block joints situated elsewhere on the rim so that they could come into prolonged contact with the skin,
e.g. nasally, shall not be masked and shall be subjected to the coating test.
The grooves of rims do not need masking, but they can be masked during this process in areas adjacent
to lugs and where pad arms had been attached. If, however, the frame has been submitted to the
simulation of wear test (6.2) without lenses, the groove shall be masked.
Mask all soldered joints that will be immersed in the saline cell, e.g. mask the areas where the bridge and
bracebar, if fitted, is soldered to the rims.
Other parts to be masked can depend upon the choice of electrical contact area and whether or not the
test sample is cut.
3)
A mechanised syringe can be helpful, e.g. the Chimetic Dosatore CH/N24V from
http://www.chimitec.com/dosatrici_uk.htm. This information is given for the convenience of users of this
document and does not constitute an endorsement by CEN of this product. Equivalent products can be used if they
can be shown to lead to the same results.
Front designs where the rims are soldered to a browbar or hood (e.g. a front sheet made from pressed
metal) should be masked on both sides of this area to avoid infiltration of saline solution, see Figure C.3
d).
Uncoated parts shall be masked. If these are intended to be in contact with the skin of the wearer, these
parts shall be tested with the migration test (Clause 8) on additional test samples. Allow the masking
agent to dry and cure completely. During this process, support the test sample so that the masked areas
are not in contact with a surface. In the case of doubt, follow the instructions of the manufacturer of the
masking agent.
If the test parts will not be tested immediately after the masking agent has dried and cured, then protect
them from potential damage by wrapping with paper tissue or placing individually in a polythene bag.
7.3.3 Determination of test area
The measured value with the coating test method is always in impedance per area, expressed in units of
Ω ⋅ cm . Therefore, the method involves a need for determination of the test area, which is the immersed
but unmasked surface area of the test sample.
. Direct measurement of surface area can be used; CAD data
Determine this test area to the nearest cm
from the frame manufacturer and/or classical picture analyser software can be helpful.
7.3.4 Preparation of electrical contact area
The following serve as the electrical contact areas:
— for sides: either the joint, or the end furthest from the joint;
— for fronts: the joint end of the lug that is not masked.
Abrade the electrical contact area, e.g. with a hand-held rotary model-making tool, file, or emery or silicon
carbide paper, so that the electrically non-conductive coating is completely removed. Take care not to
damage the coating outside the contact area during this process.
NOTE 1 It can be easier to abrade the sample before masking. Subsequent light abrasion can be necessary before
the impedance measurement, see 7.5.2.
NOTE 2 Wear suitable protective equipment, if appropriate.
7.4 Preparation of saline solution
Prepare a solution of saline by dissolving 10,0 g ± 0,1 g of sodium chloride (7.2.3) in 1 l of deionized water
(7.2.2). Ensure that the saline solution is at 25 °C ± 5 °C. Prepare a fresh saline solution after 7 d.
7.5 Procedure
7.5.1 Preparation of the electro-chemical cell
Wash the electro-chemical cell with deionized water (7.2.2) or with saline solution (7.4).
Fill the electro-chemical cell with saline solution (7.4). Change the solution at least once on each day of
testing.
Ensure that the reference and counter electrodes (e.g. calomel) have been immersed for a sufficient time
before use. If stored in a dry state they will need to be (if appropriate, filled with potassium chloride and)
immersed in deionized water or saline solution for a minimum of 8 h. The equipment therefore cannot
be used immediately after assembly.
NOTE Check that the “frit” at the bottom of the reference electrode has not been blocked or damaged. If saline
is allowed to dry out in this, then the pores in the special glass will be damaged by the salt crystals growing in them.
7.5.2 Insertion and connection of the test part in the electro-chemical cell
IMPORTANT — This technique requires, firstly, a very good electrical connection between the
electrodes, including the test part, and the potentiostat, and, secondly, a Faraday cage or other method to
shield the electro-chemical cell from stray electromagnetic radiation.
Immediately before the EIS measurement, verify that the electrical contact area on the test part is clean
and free from masking agent, and is not tarnished. If necessary, apply further abrasion to achieve this,
while taking care not to damage the coating in the test area.
Suspend the test part in the saline solution so that it is not resting on the bottom and is at a minimum
distance of 10 mm from the sides of the cell, ensuring that the electrical contact area is above the level of
the saline solution. Ensure that any area of the test part that does not require testing is either masked or
is above the level of the saline solution, while the counter and reference electrodes are appropriately
immersed according to the equipment manufacturer's instructions. Because the distance between the
test parts and the electrodes could affect the resistance in the solution, the test part, counter and
reference electrodes shall be arranged in a triangular arrangement with a separation of approximately
50 mm between each.
NOTE 1 A convenient way to do this is for the counter and reference electrodes to be mounted at the 50 mm
separation on a piece of insulating material resting on the rim of the electro-chemical cell so that they remain
permanently in the saline solution while testing. A second piece of insulating material can then be used to mount
the test part at the
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