Many people find the Sun too bright even in a Shade 12 filter, and some find the Sun too dim in a Shade 14 filter - but Shade 13 filters are uncommon and can be hard to find. If it's less than 12 (and it probably is), don't even think about using it to look at the Sun. If you have an old welder's helmet around the house and are thinking of using it to view the Sun, make sure you know the filter's shade number.
These are much darker than the filters used for most kinds of welding.
The only ones that are safe for direct viewing of the Sun with your eyes are those of Shade 12 or higher. Viewing with Protection - Experts suggests that one widely available filter for safe solar viewing is welders glass of sufficiently high number. The Bλ function is often termed a “blue light hazard” function, even though blue light has far less retinal phototoxicity than violet light or UV radiation.4,5,57 That is why the international consensus phakic standard Bλ phototoxicity function peaks at 440 nm in the blue part of the spectrum. In an adult phakic eye, the retina has the additional shielding of crystalline lens attenuation of UV radiation and shorter wavelength visible light. In an aphakic eye, UV radiation, violet light (400–440 nm) and blue light (440–500 nm) account for 67%, 18%, and 14% of potential retinal phototoxicity, respectively.55,56 Photosensitizer-mediated phototoxicity is the basis for the international consensus aphakic standard Aλ phototoxicity function used to estimate industrial acute retinal phototoxicity risks.57 The hazardousness of photosensitizer-mediated retinal phototoxicity increases rapidly with decreasing wavelength,5,47 similar to the absorption spectrum of lipofuscin in the RPE which is its primary mediator.53,54 Thus, UV radiation is much more hazardous than visible light.