Haha – great topic. Here's what I do:
* Metallics – Shake
* McCaffery's black i.e. another iron gall ink I use – stir sometimes, use often as it is
* McCaffery's ivory – stir (at the moment …)
* Walnut ink – use as it is
* Dr. Martin's bleedproof: add some drops of distilled water, stir only surface, fill the liquid stuff with a pipette in Dinky Dip and use from this. This DD then lasts quite long as I put in again some distilled water etc. …
* Pelikan 4001 – use as it is (I am curious – that's a dye-based fountain pen ink as far as I know? So why do you stir it? It's just the most commenly used ink in Germany, I think, you can buy it in little plastic containers and put it in your fountain pen, school kids use it … so that's why I am soo curious
)
* Rohrer & Klingner writing ink – put some drops of gum arabic in, then use as it is
* Ziller's ink – stir; sometimes thin it with some drops of distilled water
I don't have Sumi ink …