2005-02-18
Ferro-Gallotannic Ink
I'd been purifying Iron Sulfate by crystallisation and I had some saturated filtrate laying around, so I decided to make some Iron Gall ink.
An order of chemicals from Vanbar had just arrived including some Tannic Acid, so it was a simple matter to prepare a saturated solution of tannic acid and pipette a little into a micro-centrifuge tube, followed by some Iron Sulfate solution. A wonderful deep black solution forms, the Iron/Gallotannic complex used for centuries as a pigment for writing.
Initial efforts writing with the Pasteur pipette looked promising; "Hello World" - what else :-). But lacking a fountain pen I was stumped for a moment. Then I saw a bamboo skewer on the count top, the solution was obvious; dig out the scalpel and fashion a writing implement.
A bit of whittling and a nick out of the end and I had a crude device that would hold enough ink to get through a word or two. Hmm, would help if the ink was darker... So I made a stronger batch fiddling with the ratios a bit and boiling a little to concentrate it.
Better, but still in need of flow and hold qualities, so a pinch of gum arabic was dropped in. I wish I had one of those vibrating shaker things for centrifuge tubes, getting the gum into solution took some flailing of the arms for a minute.
Eventually I had a page covered with scribbles using ink and a pen that I made from scratch in only a few moments. Using the device and material perhaps put me in touch with the poor buggers that had to use this stuff in the past. It smudges, it runs, it takes a while to dry, it gets darker as it dries, you need to re-dip often, etc. But it works and facilitates communication like no substance before it. The impact of this simple invention must have been immense.
Which brings me to finish up with this lovely quote from the Devil's Dictionary:
Ink, n.: A villainous compound of tannogallate of iron, gum-arabic, and water, chiefly used to facilitate the infection of idiocy and promote intellectual crime.
-- Ambrose Bierce, The Devil's Dictionary
If you wish to repeat this experiment you need only boil a teabag or two in about 100 ml of water. That will be a plenty-strong solution of tannic acid, and pure enough for making ink. If you want to do it properly find some galls and boil them up. Iron Chloride from salty water and Iron electrolysis will give you the Iron ions you need, but the sulfate does work better.
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