Those are #10 welding glasses, quite bright. If you use #14 or even #13, there's no need to stack them with anything. They are sufficiently dark on their own.

Those are #10 welding glasses, quite bright. If you use #14 or even #13, there's no need to stack them with anything. They are sufficiently dark on their own. #14 are even ISO 12312-2 compliant for the purpose of eclipse viewing. Here's the best information on related topics: https://eclipse.aas.org/resources/solar-filters https://eclipse.aas.org/resources/solar-filters