You can’t look at the Sun on any day, and eclipse day is no exception. The American Academy of Ophthalmology (AAO) says so plainly: there is only one safe way to look directly at the Sun, whether there is an eclipse or not, and that is through special solar filters. The eclipse doesn’t make the Sun more dangerous, but it tempts you to stare at it, again and again, during a partial phase lasting more than two hours. The only exception is totality, and only inside the path: in Tarifa, from 10:45:11 to 10:49:38 Spanish time (CEST, UTC+2).
The same Sun as on any other day
The AAO insists that special protection is needed to look at the Sun during a partial eclipse or at any other time, and warns that looking at it without protection, even briefly, can damage the retina for good and even cause blindness. English Wikipedia puts the same thing the other way round: looking at the Sun during an eclipse is as dangerous as looking at it outside an eclipse, except during the brief period of totality.
The Moon covers part of the disc and leaves the rest as it is: what remains in view is as bright as at any other time, and the IGN (Spain’s National Geographic Institute) calculates that 1% of the Sun’s surface is enough to damage your eyes. The numbers are in don’t look at the partial phase without glasses, not even for a second (in Spanish).
What changes that day: the urge to look
On a normal day nobody stands staring at the Sun. Wikipedia explains it like this: in normal conditions the Sun is so bright that it is hard to stare at, but during an eclipse, with so much of it covered, staring becomes easier and more tempting. The eclipse also demands your attention. You want to see the bite advance, you look again every so often, and the partial phase seems to go on for ever: in Madrid it runs from 09:45:35 to 12:02:42, and in Málaga from 09:42:09 to 12:02:35. That’s a lot of chances for a glance without glasses, and all of them seem harmless because the retina gives no warning: it doesn’t hurt, and the effects can take hours to show, so nobody notices while the damage is being done. What you notice afterwards, and when to see an eye doctor, is covered in what happens if you look at the eclipse without glasses (in Spanish).
Why totality can be looked at (and only totality)
In totality the Moon covers the whole bright surface of the Sun. NASA gives this as the only exception: only then can you look without protection, and you’ll know it’s safe when you can no longer see any part of the Sun through your glasses. What is left in the sky is the corona, the Sun’s outer atmosphere. An article by the American Astronomical Society (AAS) on how dark totality gets compares it with the full Moon: it is the corona, not the landscape, that shines like the full Moon, and the light around you is about 5 lux, as in civil twilight.
NASA also marks the end: as soon as a little bright Sun reappears, the glasses go back on. The AAO says the same: during totality, and only then, you can take your protection off, and you have to put it back on before totality ends.
In Spain that happens in the 105 municipalities in the path, a few minutes before eleven in the morning and at a different time in each one. The exact second for each municipality, with the cautious rule of taking the glasses off at the later C2 and putting them back on at the earlier C3, is in when to take off your eclipse glasses in totality.
Outside the path there is no totality, however much of the Sun is covered. Almería stays at 99.9%, Granada at 99.2% and Seville at 98.4%: there the Sun never disappears and the glasses never come off. If you don’t know which side you’re on, check will I see it?.
What doesn’t protect you
The AAO warns that ordinary sunglasses, however dark, are no good for looking at the Sun, and neither are homemade filters. If you don’t have eclipse glasses, you can follow the eclipse without looking at the Sun by projecting its image. And to find out whether a pair of glasses meets the standard, see our glasses guide.
Sources: AAO — Solar Eclipse Eye Safety (only one safe way to look at the Sun, whether there is an eclipse or not; protection during the partial phase or at any other time; permanent damage even after a short time; protection off only during totality; sunglasses and homemade filters are no good); NASA — Eclipse Safety (no protection only when the Moon completely covers the Sun’s bright face; how to know it is safe; glasses back on as soon as it reappears); Wikipedia (EN) — Solar eclipse, “Viewing” section (as dangerous as outside an eclipse; easier and more tempting to stare; the retina feels no pain and the damage takes hours to show); AAS — How Dark Is Totality? (the corona shines like the full Moon; about 5 lux, like civil twilight); IGN — Cómo observar los eclipses (in Spanish: 1% of the Sun’s surface is enough to damage your eyes); times, percentages and municipalities: eclipseando data (skyfield + DE440s engine) and the IGN’s verdict.
If you would like something to keep from the eclipse, the shop prints T-shirts, mugs and posters with the name of your town, the time of its maximum and its seconds of totality. See the merchandise →
Remember: never look at the Sun without proper eye protection (filters made to EN ISO 12312-2). The official reference for safe viewing in Spain is the IGN (in Spanish): eclipses.ign.es.