Author: aokereyewear

Usually there is a plating/painting layer on the surface of metal eyewear, there are following simple aspects to judge the plating or painting quality of metal eyewear.

Appearance

Observing metal eyewear plating layer, no pitting and uneven place, if there are pits or uneven place, the quality of metal eyewear is relatively poor.

It also can try to get metal eyewear cross on white A4 paper, see if there are any fading.

Touching

Metal eyewear under the rub with fingers, or gently claw with nails, see if there are any fade or the fingers tinted with painting colors. The quality of metal eyewear better, the fade or tinted won’t occurred.

Previous article we briefly introduced how to identify painting or plating finish for metal eyewear.

As we understand generally plating finish metal eyewear more firm and compact than the painting finish metal eyewear. According the disadvantages, how to make painting metal eyewear more firm and compact?

Normally, before metal eyewear painting processing, it should be plated a layer of chrome finish first, it can make painting metal eyewear as firm and compact as plating finish metal eyewear.

Chrome finish divide into white chrome and black-chrome finish. Black or matt black metal eyewear used black chrome finish; other painting metal eyewear used white chrome finish. To take an example, White, Red, Blue, Green, Purple, Yellow etc…

Why chrome finish can make painting finish metal eyewear as firm and compact as plating finish metal eyewear?

This is because chrome finished metal eyewear surface can form a honeycomb-like structure, which greatly improved the adhesion of painting on metal eyewear. Below picture under microscope for reference.

As for a metal eyewear supplier, the disadvantage of Chrome finish metal eyewear is that it is high difficult to rework .

During the metal eyewear production, the last producing process is painting or plating finish.

Painting or Plating finish is to spray or plating a layer of protective material on the metal eyewear; it can make the metal eyewear more beautiful, shiny, and more anti-corrosion.

How to identify the metal eyewear is painting or plating finish?

Generally, metal eyewear plating only three types: gold, silver, and gun with various colors such as light, middle, and dark colors.

Except for gold, silver, and gun, all other metal eyewear colors are panting finish.
To take an example, Black, White, Red, Blue, Green, Purple, Yellow etc…
These metal eyewear colors are all painting finished.

Compared with painting metal eyewear, plating metal eyewear plating layer is more firm and compact.

Choosing the perfect metal eyewear is not easy; learn how to buy high quality metal eyewear is very necessary. Following points to help consumers understand more about high quality metal eyewear.

High quality metal eyewear features
(1) Perfect surface finish
(2)Coating layers perfect firmness
(3) Welding perfect firmness
(4) Assembly perfect and high precision
(5) Anti-corrosion. High oxidation resistance and high corrosion resistance
Low quality metal eyewear does not shine, corrosion resistance is not good.

Low quality metal eyewear features:
(1) Material hardness is not enough
(2) Metal eyewear arms bending easily broken
(3) Weld is not strong, easy weld removal
(4) Surface roughness and graceful
(5) Low assembly accuracy, different sizes on left-right rims

In the earlier days, pure titanium metal eyewear processing is major on pure titanium, but in order to greatly pursue metal eyewear strength, flexibility, and improving welding difficulty grade, other metal elements such as aluminum, vanadium, molybdenum are added in pure titanium metal eyewear.

As pure titanium metal eyewear processing techniques and workmanship are difficult, titanium metal eyewear is high valued-added and sells much expensive than normal metal eyewear and has becoming the fashion trends, pure titanium is one favorite eyewear material now widely used in optical frame and sunglasses model. Refers to pure titanium metal eyewear, it means titanium components reaches to 99% or more. It has some difficulties in machining processing, welding, electroplating and so on, so the pure titanium application is subject to certain restraint.

In order to identify pure titanium and titanium alloy metal eyewear, consumers can refer to the below two points.

Pure titanium metal eyewear was marked with the abbreviations or full name in the frame, usually on the temples or on demo lens. It marked “Ti” “Ti-P” or “ Pure Titannium” or “Titannium”.

Usually, titanium alloy metal eyewear was marked with abbreviations in the frame, on the temples or on demo lens. It marked β-Ti or β-Titanium.

Pure Titanium metal eyewear light weight, generally, pure Titanium metal eyewear 48% lighter than ordinary metal eyewear.

Pure Titanium is a kind of very special metal material which is widely used on space exploration, ship building and human’s medicine instrument, pure Titanium metal eyewear has good anti-corrosion feature.

Pure Titanium metal eyewear high toughness, high stability which anti acid and alkali liquid.

Pure Titanium metal eyewear friendly to human’s body. Its surface can do colorful anodized finish.

With people’s living standards and technology improving, pure Titanium metal eyewear is becoming more and popular because of its excellent performance. pure Titanium is one kind favorite material which is widely used in various optical frame and sunglasses styles.

Nickel release test principles

Put tested metal eyewear sample into in artificial sweat for 7 days, using the atomic absorption or inductively coupled plasma spectroscopy dissolved concentrations of nickel. Nickel emissions are represented by μg/ｃ㎡/week.

Test reagents
All reagents for analytical purity or higher level and contains without nickel. Demonized water, sodium chloride, DL-lactic acid, urea, ammonia, nitric acid, degreasing solution.

Pretreatment equipment
PH meter, thermostatic water bath.
Metal eyewear sample pretreatment

Preparation of test solution
Artificial sweat test solution consists of demonized water and contain: 0.5% sodium chloride, lactic acid, 0.1% urea, ammonia 1%.Before use, ensure that the pH of the solution within the 6.40~6.60.The test solution should be used within 3 hours of preparation.

Release procedures
The metal eyewear sample is put in brackets and suspended in test container. Adding a certain amount of approximately 1mL/c test solution to test square meters area.
Suspension metal eyewear sample shall be completely immersed in the test solution. Note the sample size and the volume of the test solution. Test liquid tightly closed containers to prevent evaporation. Smoothly and keep the container in a constant temperature water bath (30 ± 2) ℃, 168H, don’t stir.

After 7 days, take out of metal eyewear samples from test liquid,clean with a small amount of demonized water, will join the test with a clean solution. transfer to a volumetric flask of appropriate volume of test solution. In order to prevent the dissolution of nickel deposits added to the test solution dilute nitric acid and deionized water, its sizing to the nitric acid contains about 1% after the score.

At least do 2 set of the same metal eyewear samples.

Blank test
Repeat the blank test should be carried out in parallel with the test samples. Use the same container and bracket, the same program, Captain no sample in the container. Using the same amount of test liquid, washing liquid and dilute nitric acid.

Sample test
Instrument
Atomic absorption spectrometers.
Method
Place the flask in an atomic absorption spectrometer, atomic absorption spectrometers the wavelength adjustable to 232.0nm, spectral bandwidth: 0.2nm, record the nickel concentration in the solution.
Count
Metal eyewear sample nickel release rate d, represent as (μg/ｃ㎡/week), according to the following formula:
d = V(C1-C2)/1000A
V – the volume of the test solution, mL
C1 – 7 days after the nickel content of the test solution, μ g/l
C2 – 7 days after the nickel content of the blank test solution, μ g/l
A – sample surface area c㎡.
Calculation result to two decimal places.

Calculate d multiplied by 0.1-adjusted rate of nickel release test results. If test result more than 0.5μg/ｃ㎡/week, can verify that the nickel release rate exceed of standard.

In the daily life, why some metal eyewear cause wearer skin allergy?

It is mostly associated with excessive release of heavy metals elements in low quality metal eyewear. Especially nickel release harmful to the environment and human health. However, low quality metal eyewear adopts low cost of nickel plating.

For daily life, low quality metal eyewear in contact with the skin for a long time, wearers sweat cause nickel elements high erosion activity, the nickel cause skin allergy.

Release amount of nickel had become a topic of concern in the field of metal eyewear product quality. The International Organization for Standardization (ISO) and European Organization for Standardization (CEN) have strict management measures on the release amount of nickel.

This article studies the nickel release test methods, reference for related metal eyewear wearers and eyewear companies to reduce low quality metal eyewear harm to people.

Nickel is a heavy metal elements likely cause of allergy in human’s skin. Medical observation proves that long-term exposure to nickel-containing objects can cause skin allergies and even cancer. Excessive amount release of nickel in metal eyewear can result in harm to human health. International Organizations and the European standardization organization (CEN) have strict management measures on this.

EU countries have strict rules and standards for metal eyewear. Metal eyewear won’t allow to sale to consumers with excessive nickel release amount. In June 1994, EU issued a 94/27/EC directive, providing standard for release amount of nickel. In July 1997, the EU released 3 harmonized standards, defines the method of a qualitative analysis of nickel amount of release. ISO/TS24348 method for detection of nickel release in 2007 of the officially promulgated, which expressly provides that: Metal eyewear with the wearer’s skin and prolonged exposure to nickel and alloy components of release amount shall less than 0.5μg/ｃ㎡/week.

To be issued by the ISO12312-1 of the sunglasses are a direct reference to the provisions and requirements: Sunglasses designer and manufacturer shall not endanger the health or safety of the wearer, and should minimize the risk of possible damage the wearer’s skin by the lens or frame material.

Korea technical standards (KATS) published belongs to the proposed modifications to the safety and quality mark for industrial products, this proposal seeks to amend the safety and quality standard in sunglasses and optical fame, the release of nickel for sunglasses and optical frame to adjust to less than 0.5μg/ｃ㎡/week.

From the current status, Chinese eyewear products accounted for more than 70% of the world’s total eyewear production amount, and exports more than 60% to the international eyewear market. However many domestic manufacture of metal eyewear adopts low cost of nickel plating.
Since International Organizations (ISO) and the European standardization organization (CEN) have new stringent requirements of release amount of nickel, which brought a great impact on domestic eyewear industry, it becomes necessary for well understanding production method for the detection of nickel release.

As a professional metal eyewear manufacturer, we adhere to the ISO and European Organization for Standardization (CEN), we cooperate with quality electroplating factory and signed contracts and agreements related to the nickel release test. Each batch of metal eyewear should pass through the nickel release test.

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