Safe glasses for Spain's total eclipse: where to get them for free

Published on 05/08/2026 - 5:58 GMT+2•Updated 8:11

Remember this figure for the eclipse that will cross the Iberian Peninsula on 12 August. Keeping that date in mind, the ISO number (International Organization for Standardization) of the special glasses that must be used to view this once-in-a-century phenomenon safely should be easy to remember: 12312-2015.

Without them, ultraviolet radiation will damage the eye’s photoreceptors (cones and rods), while infrared energy will produce a direct thermal effect on the retina, causing solar retinopathy. Symptoms of this condition, which may take time to appear, can include blurred vision, spots or scotomas at the point of greatest visual acuity, metamorphopsia (distorted perception of shapes) and reduced tolerance to light, or photophobia, which can lead to headaches.

The total phase of the eclipse will not last more than 1 minute and 48 seconds - the closer you are to the line of totality, the more seconds you will be able to enjoy the event - anywhere along its path across Spain. It is in that brief moment that lucky observers may remove their approved glasses.

ISO standard 12312-2 applies only to certain products designed for direct observation of the Sun, or what astronomers call the photosphere: the Sun’s bright face. These products ensure that no more than 0.00032% of visible sunlight is allowed through. The Ministry of Science explains that "you must put the glasses on before looking at the Sun, look briefly for a few seconds and then lower your gaze, repeating observation of the eclipse always with pauses". You should not take them off before you stop looking at the Sun.

The standard applies only to glasses without any change of prescription or focus. It does not cover ordinary sunglasses (ISO 12312-1), which allow hundreds or thousands of times more light to pass through than is safe for looking directly at the Sun, nor solar filters designed for devices such as telescopes or binoculars. It also does not apply to solar filters designed to be placed over the aperture (front) of optical devices such as camera lenses, binoculars or telescopes.

The key requirements are transmittance (the ratio between transmitted light and incident light) at ultraviolet, visible and infrared wavelengths that reach our retinas; the uniformity of that transmittance; and the appropriate quality of the material. The Scientific and Advisory Commission of the Eclipse Trio adds that, if they are sold in the European Union, they must also bear the CE mark.

The Ministry and ONCE are going to distribute two million certified safety glasses free of charge at stands run by the latter foundation and at research centres, science museums and other public bodies. Several autonomous communities will also hand out certified equipment at designated locations for viewing the astronomical event. Here is the list of places where you can get the glasses free of charge (source in Spanish).