Im not an egg expert. Dad used Borax. But in those days, they didnt have all the colors etc we do now. Borax seems to toughen up the eggs.

I have all the old photos. They didnt need GL2 or better, invisible line, lazer hooks. Hell, the first mono was dark brown. He even used it for his hand tied flyline leaders, cause the line was stiffer and rolled out a better cast. My Dads boss, came up with the idea for weighted flylines and told the flyline guys to use powdered lead. They just mixed it into the batter.