Eclipse glasses: what to buy and how to spot a fake

Eclipse glasses cost very little and are the only thing standing between an unforgettable morning and permanent retinal injury. The problem is that the market fills with counterfeits in the months before every eclipse, and they are indistinguishable from good ones by eye.

What certification they need in the EU

There is a widespread confusion worth clearing up. The international technical standard is ISO 12312-2, which defines how much light the filter may transmit. But in the European Union eclipse glasses are also Category II personal protective equipment, governed by Regulation (EU) 2016/425. That means that to be sold legally in Spain, meeting the ISO standard is not enough: they need CE marking backed by an EU type-examination certificate issued by a notified body.

• Look for the CE mark followed by the notified body's four-digit number.
• Look for a reference to EN ISO 12312-2, the European version of the standard, identical to the international one.
• Look for the name and address of the manufacturer or the EU responsible person. With no identifiable party, there is nobody to hold accountable.
• Be wary of anything that says only 'ISO 12312-2 certified' with no CE mark and no notified body: this is common on imported stock and does not meet EU requirements.

How to check a pair you already own

• Put them on in a lit room. You should see absolutely nothing except a very bright bulb. If you can make out furniture or windows, bin them.
• Hold the filter up to a light and look for scratches, pinholes or creases. Any defect makes them useless.
• Check the filter is firmly bonded to the frame and not lifting at a corner.
• Discard any that are crumpled, folded, or have been loose in a drawer since a previous eclipse.

How many you need and when to buy

One per person, not shared: passing a single pair around during the partial phase is the easiest way for somebody to look at exactly the wrong moment. Buy months ahead. At recent eclipses, certified stock sold out weeks in advance, and what remained at the last minute was precisely the material with no traceability. If you are travelling in, buy from a recognised supplier at home and bring them with you.

Safe alternatives without glasses

• Pinhole projection: a card with a pinhole projects the Sun's image onto a second card. You never look through the hole.
• A kitchen colander projects dozens of crescent Suns onto the ground. It works best with children.
• The shadow of a tree does the same through its leaves, free and with no preparation.
• Projection through a telescope or binoculars onto card, never looking through the eyepiece.

And during totality

In Ceuta, during the 288 seconds of totality, the glasses come off. Taking them off is necessary to see anything at all: through the filter the corona is invisible. And they go back on the instant the first flash of light appears at the edge.