Hatam Soferet

The main thing about Torah ink is that it has to be black and it has to stay black. If it changes colour within fifty years, it wasn't kosher to begin with.

Generally, Torah ink (דיו, in Hebrew, like dye) is what's called an iron gall ink. Iron gall inks have been used in a great many places during a great many periods in history. They last a long, long time (think Dead Sea Scrolls kind of longevity). They have an unusual property among pigments in that they form chemical bonds with the parchment, which makes them symbolically very appropriate for use on Torahs. They are lightfast, the ingredients are cheap, and they are very indelible.

I don't make my own; making good ink is hard, and I don't have anyone willing to share their recipe. Anyway, it's supposedly rather a pain, so I buy it in bottles, as shown. I don't know if it's also available in cake form - cake is much easier to transport, of course, and lasts longer, and is entirely traditional. I suspect perhaps not, because I have a feeling that buying ink like this is kind of For Dummies, and real hardcorers, the kind who would want cake ink, probably do make their own.

As you might expect, there are hundreds of different recipes for this kind of ink. However, they have some things in common, viz.: gallnuts, iron (II) in solution, something runny, and something sticky. The following descriptions are indebted to an excellent article by Cyntia Karnes.

Gall nuts

See the Wikipedia entry, but basically gallnuts (also called oak-apples) are a sort of arboreal tumour. A gall wasp comes along and lays its egg on the tree, and the tree goes "whoa" and swells up around the egg, into this little hard ball. The larva sits inside the swelling, munching away, and when it grows up it eats its way out and leaves the ball on the tree.

The balls have to be turned into a gloopy solution. This basically involves grinding, dissolving, and fermenting, and there are about a zillion ways of accomplishing this. Depending how it's done, what you end up with is a liquid containing tannic acid, gallotannic acid, or gallic acid.

I'm very fond of these diddy little inkwells, and I have several kicking around the place. Today, I found a random one in the fridge (I keep inks in the fridge, cos they can grow mould if you don't). What's in it?

There are only two sorts of ink the mystery bottle can contain, at present, cos I only have two kinds of black ink in the house. One of them is kosher, and I can use it on the Torah, and one of them isn't, and I can't use it on the Torah, and if I do the Torah will be pasul. Invalid. Bad news. I could taste it and work out what it is, but ink tastes vile, sofer's ink more so, so I'd rather not.

Science to the rescue! Colour chromatography.

By way of illustrating the method, first we'll compare two known inks.



You take two strips of kitchen roll, and put a blob of ink near the end of each. Properly, you hang the strips vertically because the reason it works has to do partly with gravity, but for this kind of thing you can just drape them over a plate and it works fine.

Then you dip the ends in water, and see what happens!


The different pigments move through the paper at different rates, and separate out, so you can get an idea of what's in the ink. The sofer's ink mostly stays black, with a sort of pink tinge round the edges, and Brand X goes all kinds of colours - yellow at the top, blue at the bottom. It also spreads much further, because it's more water-soluble (sofer's ink binds chemically to natural fibres) it looks like there's just more of it in the picture, but I used the same amounts - Brand X spreads even before you wet it, that's all).

So, now we can find out what the mystery ink is.

Two blobs on dry kitchen paper, draped over a plate, same as before. Wet the ends...

...and we see no blue, no yellow, only the pink tinge and the limited spread, just like the one we know for sure is sofer's ink. So it must be sofer's ink.

Hooray for science!