Onionskin dyeing the wool

QUESTION: Is it true that black wool dyed with yellow onionskins turns green? This I heard and set out to research. The nice people at my friendly local natural foods store, Sundance, save me some onionskins.

Supposedly you need no mordant for onionskins, but alum makes it brighter. So what is this alum, and where to find it? Turns out your local grocery store has it, but after calling around several stores I find that very few store workers know what it is. Finally I look it up on wiki and tell the clerk to look in the spice section. It is used for pickling, and comes in powder form.

Rainwater works best, so I'd been told; so I make use of the snow that happens to be making its once  or twice a year appearance. Wow, it takes several buckets of snow to make one bucket of water.

Stuffing as much onion peel into the pot as I can, adding more as it wets down, I boil for a few minutes, simmer a few more, strain, stir in the alum, and put in my freshly washed fleece. I let it  boil a few more minutes with the wool, then rinse and let it drip outside on the deck.

ANSWER: No. Onionskin dyeing does not turn black wool green. The blond Churro wool is a lovely marigold now.

The brown Jacob wool with blond tips is now brighter brown with pumpkin tips.

  The "blue" grey wool from Rhapsody,  a Churro sheep who lives in Brownsville, is now a warm grey with flaming tips.

As for the black, it is still black. Kinda has a henna sheen though.