Anyone can print "ISO 12312-2" on a paper frame. The words cost nothing and mean nothing on their own. Here is what the standard actually requires, and the six documents that separate a supplier who has tested the product from one who has copied a certificate off the internet.
What ISO 12312-2 actually tests
ISO 12312-2:2015 covers filters for direct observation of the Sun. It is not a general sunglasses standard and it is far stricter than one. The core of it is spectral transmittance measured across 280 to 1400 nanometres, with separate limits in three regions:
- Ultraviolet, 280 to 380 nm. Effectively everything must be blocked.
- Visible, 380 to 780 nm. Luminous transmittance must fall inside a very narrow band, roughly equivalent to welding shade 12 to 14. Too dark is a failure as well as too light, because a filter you cannot see the Sun through invites people to take it off.
- Near infrared, 780 to 1400 nm. Limited to a few percent. This is the region that does thermal damage to the retina and the one cheap filters most often fail.
Beyond transmittance the standard also sets requirements on uniformity across the filter, on freedom from defects such as pinholes, bubbles and scratches, on mechanical robustness, on flammability, and on the labelling and instructions that must be supplied with the product. A filter can pass the spectral test and still fail the standard on a pinhole.
The six things to ask for
1. A test report that names your product
Ask for the full report, not a certificate summary page. Read the sample description. It should identify the specific filter material and product being sold to you. A report describing a different model number, or a generic "solar viewer", is a report about something else.
2. The testing laboratory's accreditation
The report should come from a laboratory accredited for this scope of testing. Check the accreditation number and the scope, not just the logo. A lab accredited for sunglasses to ISO 12312-1 is not automatically accredited for solar viewers to 12312-2.
3. An EU type-examination certificate, if you are selling into Europe
Solar viewers are personal protective equipment under Regulation (EU) 2016/425 and fall in Category II. Category II requires EU type-examination, module B, carried out by a notified body. The certificate carries a number that begins with the notified body's four-digit identifier. You can look that identifier up in the European Commission's NANDO database and confirm it is a real notified body with PPE in its scope. Ours is 0068-PPE-0187.
4. A Declaration of Conformity
The manufacturer draws up an EU Declaration of Conformity and affixes the CE mark. The DoC names the product, the legislation, the harmonised standard applied, and the notified body and certificate number. As an importer you are required to keep a copy of it for ten years. If a supplier will not give you the DoC, you cannot legally place the goods on the EU market, whatever else they send you.
5. Lot traceability tying the report to your goods
This is the one buyers skip and it is the one that matters most. A test report proves that a sample tested well on a date. It says nothing about the cartons on your pallet unless there is a lot number connecting them. Ask how lots are numbered, where the number is printed, and ask for the batch test record for the specific lot you receive.
6. Independent recognition of the manufacturer
The American Astronomical Society's Solar Eclipse Task Force maintains a list of suppliers whose products it has reason to believe are safe, based on test reports it has reviewed. It is not a certification body and its list is not a legal requirement, but a manufacturer that appears on it has had documentation examined by people who know what they are reading. We are on it.
Checks you can do yourself in five minutes
These will catch a crude fake. They will not catch a filter that fails only in the infrared, which is why they do not replace laboratory testing or documentation.
- Hold a pair up to a bright household lamp. You should see the filament or the LED array only faintly, and nothing else in the room at all. If you can make out the shape of furniture, the filter is far too light.
- Hold the filter to a strong light and look across its surface for pinholes, scratches or thin patches. Any point of bright light through the film condemns the pair.
- Check the tint is even across the whole lens, with no mottling or streaks.
- Read the frame. It must carry the safety warnings, the manufacturer's name or trademark, the standard reference, and for EU sale the CE mark. A frame printed only with a brand logo is not compliant regardless of what the filter does.
- Check the instructions are supplied in the language of the country you are selling into. This is a legal requirement, not a nicety.
If a supplier sends you a certificate as a flattened image with no readable certificate number, or a report whose lab you cannot find, treat that as the answer. Genuine documents survive being checked.
How we handle it
Every incoming filter batch is tested in our own laboratory before it goes into production, and a batch that fails does not get used. After production, random samples from the finished run go to MTIC, an EU notified body, for testing to EN ISO 12312-2:2015. We accept third-party inspection before shipment and we accept testing at a laboratory you nominate, on samples drawn from your own production lot.
The test report, the type-examination certificate and the Declaration of Conformity go out on request, with no non-disclosure agreement attached. You can read them before you place an order, which is the only sensible time to read them.
The certificates and downloadable Declarations of Conformity are on our documents page.
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