by Brian G. Walker
I thank Nan and others for the positive comments re my ink, appreciated, but Nan's remark --
They came out dark (not as dark as Sumi) but way thinner hairlines
--raises a couple of interesting points about the darkness of iron gall ink and about hairlines.
The science of iron gall ink is highly complex and I don't profess to understand it all or be able to explain it easily. However, one usually reads that iron gall ink, being chemically based rather than carbon based, first appears grey on the paper and then darkens as it oxidises - a natural occurence. But in fact there are several methods one can use in the making process to achieve an excellent black ink even before it's bottled. Black ink straight off the pen tip. In theory, the marks made, being already black, should then darken further still as the ink 'ages' and so be just as compatible with any carbon ink. The addition of dyes such as logwood and indigo can also act as additonal darkeners.
How much though an iron gall ink will darken on a page is as much to do with the writing material as the ink itself.
Iron gall ink works on the principle of 'striking' into the support material. The 'indelibility' of the ink is one reason why it was used extensively throughout the Middle Ages and in legal documents. Carbon ink could easily rub off in the process of the book or manuscript being handled or at worst, removed from the page altogether so the vellum could be re-used.
Once on the paper iron gall ink will be influenced by the substrate itself. This substrate may be cellulosic or proteinaceous in make up or may even contain alkaline materials, which may neutralise the acidic properties of the ink. In other words, because of these factors, the ink may not 'strike' as effectively, darken as quickly or as easily on one paper as it may on another.
I've found my ink is instantly black on Character Hi White Wove and several copier papers, whilst on Clairefontaine with its smooth bright sheen, less so. The ink also works well on some calligraphy papers, but not as effectively on others, although I'm more likely to be using gouaches, carbon inks or mixtures of the two on papers such as Saunders Waterford and Aquarelle Arches. Therefore it's worth remembering that one combination of calligraphic media will tend to work better than another combination. It's always best to experiment with any art materials (and materials to fit the purpose) before reaching any definite conclusions.
There's so much written about iron gall ink corrosion and this is certainly a difficult problem for conservators (hence the science involved) although let's not forget that hundreds of manuscripts and drawings done in iron gall inks have been stable for many centuries. But what interests me most is that such great artists of the past as Leonardo da Vinci, Rembrandt and Vincent Van Gogh all used iron gall ink for their drawings. And of course it was the favourite ink of the American master penmen during the Golden Age of Ornamental Penmanship. Iron gall ink is now enjoying something of a calligraphic revival, but more needs to be understood about it.
At the end of the day, if it's purely blackness you're after, then use Higgins or black gouache. But if it's beautiful line quality and subtlety of shade you feel to be more important in some aspects of your pen work, and if you want hairlines that really are as thin as hairs almost invisible to the naked eye, then there's no argument.
I hope these few personal thoughts make sense, are useful and I hope at least most the facts are fairly accurate.