I started a small vinegaroon batch 2 days ago with some rusty springs and some chinese rice vinegar(Pearl River Bridge brand) from the local oriental food store. Half a Litre of vinegar was £0.89, around a Dollar 29. I'm sure I'll find it cheaper, but I bought retail just for the experiment.
I wanted to try the rice vinegar out as I do a lot of Asian cooking and I'd noticed the smell was much less pungent than using regular white vinegar.
So, I cut a piece of 5-6 veg tanned shoulder and dipped it for 2 minutes. The solution was the colour of weak tea. It turned the leather a lovely dark steel grey, almost a charcoal black.
I made a strong solution of Sodium Bicarbonate and tapwater to neutralize it and soaked it through for a couple of minutes. Just for the sake of being thorough, I then rinsed the piece in running tap water.
Once oiled, the piece turned a really nice deep black. I let it dry and gave it a coat of Resolene.
There is a very slight metallic odour. Other than that it really doesn't smell at all, certainly not the strong vinegary smell I'm used to. I thought the Bicarb might help. I think the net result is a combination of the less pungent rice vinegar and the Bicarb bath.
Cheers
Karl