Apparently there are some very unscrupulous people who are faking their solar eclipse glasses to make it look like legitimately rated ones. It goes without saying that if you don’t have legitimate solar eclipse glasses then don’t even think about looking directly at the eclipse, no not even with layers of polarized sunglasses. If you can’t find them last minute then make an eclipse projector box such as the suggestion from Popular Science or this pinhole model . However now that I know that there are people who are low enough to fake out eclipse glasses just having ones rated is insufficient comfort for me. So, how do you make sure you don’t burn out your eyes using some something some POS manufacturer cranked out (they should be prosecuted)? You test! These are the tests I’m doing to confirm for me I can safely use my own glasses to view the eclipse. Use any of these steps at your own risk.
Solar eclipse glasses block out a lot of light. You therefore want to confirm that they are actually doing this correctly. First test, look through them and look outside in bright sunlight. You see anything? If you do your glasses aren’t going to cut it, go get new ones or make one of the reflector boxes. Even if you are looking at a shiny glint point, on say a reflective car bumper, you still won’t even see that unless you are right on top (within several feet) of it and even then it will barely make it through. So if you have passed those tests with flying colors next fire up a light bulb and look at it with the glasses. If you have a CFL bulb you can get right on top of it and barely start seeing it. If you have an LED or incandescent bulb you will actually be able to see the filament if you get within several feet of it but that’s pretty much it. If looking at any of these hurt your eyes or if they seem bright then, again, your glasses aren’t going to cut it. After these tests I then tried looking at the sun briefly in no eclipse (today), and sure enough it’s a very dim orange disk. I’m therefore as sure as I can be that these will protect me during the eclipse viewing. I guess there is the possibility it is only blocking visual and not UV light but it seems that is more trouble than it’s worth. Since I’m trying to filter out the unscrupulous people when all these tests are met I consider my glasses safe. If you have any lingering doubts or want to be even more cautious then just use the reflector box method.
In summary, if you have no glasses (or damaged glasses) use a reflector box. If you have glasses take a few minutes to do the steps above to make sure they are legitimate so you don’t end up regretting it the rest of your life. Here is some additional safety information from NASA: https://eclipse2017.nasa.gov/safety