Solar eclipse 2027 › Eclipse glasses
How to choose reliable ISO 12312-2 eclipse glasses
Direct viewing during the partial phases requires a solar viewer made for that purpose. A printed standard number is a starting point, not proof on its own. Check the manufacturer, instructions, seller information and physical condition together.
What ISO 12312-2 means
ISO 12312-2 specifies requirements for filters intended for direct observation of the Sun. It controls transmission of visible light and radiation that can injure the eye. For an English-speaking buyer, the key point is that this is the same standard recognised internationally for eclipse viewers.
Ordinary sunglasses do not meet this purpose, regardless of how dark they look. A generic compliance mark is not a substitute for an explicit reference to ISO 12312-2 and traceable product information.
Signs of a reliable solar viewer
- Legible standard and instructions. The viewer should state ISO 12312-2 and explain safe use in language you understand.
- Identifiable manufacturer. A company name and a clear way to trace the responsible business should be present.
- Consistent seller information. Avoid listings that mix brands, product types or photographs, or conceal who supplies the viewer.
- Uniform, secure filter material. The film should sit flat, remain firmly attached and show no light patches.
No single logo settles the question. A counterfeit product can copy a standard number. The marking, manufacturer, seller, instructions and construction must all make sense together.
How to spot a counterfeit claim
Be cautious when the manufacturer cannot be traced, the standard is visible only in edited product images, or the listing makes vague claims such as “complete protection” without technical identification. Inconsistent packaging and missing instructions are further warning signs.
Do not rely on darkness as a test of safety. A material can look almost black while transmitting harmful radiation. Home-made filters and unidentified film should not be used for direct solar viewing.
Inspect every filter before use
Discard a viewer with scratches, pinholes, tears, deep creases, detached edges or uneven transparency. Check it in normal indoor light without looking at the Sun. A bent frame that leaves gaps around the eyes is also unsuitable.
Put the viewer on before looking up. Turn away from the Sun before removing it. Follow the manufacturer's instructions for storage and use, and inspect the filter again whenever it is brought out.
Can older eclipse glasses be reused?
Age alone does not decide whether a viewer is safe. Reuse is reasonable only if the product meets ISO 12312-2, has been stored according to its instructions and remains completely undamaged.
Do not use a viewer that has spent a long period folded, loose in luggage or rubbing against other objects. If its history or condition is uncertain, do not take the risk.
Planning for a group or family
Each person who intends to look directly at the partial eclipse should have a viewer that fits and can be controlled safely. Carry spare compliant viewers so a damaged filter does not lead to improvised sharing or unsafe substitutes.
An adult should check the fit for children and supervise every direct look during the partial phases. If that supervision cannot be maintained, use pinhole projection and observe only the projected image.
If reliable glasses are unavailable
Do not look directly at the Sun. Make a pinhole projector with a small hole and a light surface, or use the holes in a colander to cast multiple solar images. Look at the projection, never through the hole or colander.
Projected crescents under trees are another indirect way to follow a partial eclipse. These methods are useful for groups, but they do not replace the front-mounted filter required for an optical instrument.
Binoculars, telescopes and cameras need different filters
Eclipse glasses are for unaided direct viewing. They must never be used behind binoculars, a telescope or an optical camera viewfinder.
A suitable solar filter must cover the front of every objective and be secured against slipping. Never attach a solar filter to the eyepiece. Concentrated sunlight reaches that point before the filter and can break it or injure the observer.
When the glasses may come off
The sole exception is complete totality, only from a point inside the path and only while the entire solar disc is covered. Put the viewers back on at the first returning point of light, including Baily's beads or the diamond ring.
Outside the path there is no exception at any moment. Read the full eye-safety guide, then confirm the observing point in the where-to-see guide.
Last updated: 14 August 2026 · Editorial team