Someone asked the same question at MPAS and this was the response:
Welding glasses are not suitable for direct viewing of the Sun. These
glasses are designed to absorb UV light from the electric arc but pass most
of the IR. This IR component can also damage you eyesight.
You can use high density welding glasses to look at the Sun in reflection.
Only about 8% of the energy is reflected from a glass surface. Just a plain
piece of glass in conjunction with the welding glasses is OK.
This is the method used in a number of solar telescope designs.
Do not use the welding glasses over the aperture of a telescope or
binoculars. This just makes the problem worse.
I know nothing about welding glasses so this is just a copy and paste of the response.
No problem, just don't use them when looking through bino's or a telescope. Any magnification (read: concentration of heat) and they will crack. After all, they are welding glasses, they block light, not heat.
