The Power of Apple Cider Vinegar for Rust Removal

I guess I should have said per 1 cup because washing soda is powder and ash is flakes and doesn't weigh as much
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I see what you're saying. I used the term soda ash but I was talking about the washing soda. So you're probably right the different names have different weights because of different ways of processing although the same chemical composition.
But isn't a pound a pound whether it's a flake or a powder.?

barbee.
Are you talking about Oregon vinegar. If so it's called that because it's processed in Oregon.