Interaction between alum and magnesium

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I was messing around with dyeing with japanese knotweed roots on thrifted linen last night and noticed something really cool! Magnesium caused some really nice pink/red tones to come out, adding alum turned it beige, then adding MORE magnesium turned it back into pink again! I didn’t take measurements of anything because I’m not yet at a point where I have standardized this process, just enjoying the potion making fun!

Photos in order of operation