Is simple enough. Making the perfect ink is a little hard.
Nevertheless, a couple of days ago I tried making ink. I ground 2 oak galls up, boiled them in water for 10 minutes or so which had some malt vinegar added which allegedly helps extract and break up the tannins, filtered the solid bits out and was left with a brown solution.
I then added a solution of iron vitriol to it:
You can see the brown solution changing instantly to black as the iron reacts with the tannins and the acidity of the sulphate splits apart more tannate to react with the iron. It’s nice to see, and doing it in this way means I can control the amount of vitriol added, meaning there isn’t too much iron and sulphate so it won’t rot the paper over the coming centuries.
I boiled it down, stirring often because otherwise a film formed on the liquid. I don’t know what it was and am reluctant to guess at this time.
Then I added some gum arabic, probably not enough since the ink was still a little runny, but I was able to write perfectly with it and it produced a lovely black.
What is a little odd is how purple it is when fresh. I wrote a little with it and spilt some on my worksurface, and it was distinctly purple. This effect faded away by the time the ink was a day old though, and the internet suggests, sensibly, that once the ink has been oxidised some more the purple goes away.
So that’s my best batch of ink yet. The thing about oak gall ink is that you don’t really need to pay much attention to the recipe, just make sure the right things are in there and boil it to the right consistency at the end. Since there’s so much variation in the original recipes, this approach works fine. Also it is a little hard to weigh out the ingredients when you are making just 10 or 15ml of it, since 2 oak galls together weigh about 5gms or so.