have you already discussed this , or have any explanation for it ? the letters also seem slightly smaller in this line.....weird
Very good observation, NO !
No, we haven't discussed this, but medieval ink should not discolor like that.
The galls contain large amounts of tannic acid, which was used for making iron gall ink and for dyeing cloth. According to recent research, traces of iron-gall ink have been found on the Dead Sea scrolls and on the 'lost' Gospel of Judas. Iron-gall ink may have been used for 1,800 years, but it does not withstand the test of time well. Over the course of centuries, the ink fades, and discolours and damages the paper. Other water-proof formulae, better suited for writing on paper, became available in the 20th century. Iron gall ink is manufactured chiefly by artists enthusiastic about reviving old methods or possibly forgers of old documents.
A recipe for preparing the ink is as follows: Take one lb. of bruised galls, one gallon of boiling water, 5½ oz of ferrous sulfate in solution, 3 oz of gum arabic previously dissolved, and a few drops of an anti-septic, such as carbolic acid. Macerate the galls for 24 hours, strain the infusion and add the other ingredients.
British galls have too little tannic acid (about 17%) for the best results - Aleppo galls have three times as much
Iron gall ink (also known as iron gall nut ink or oak gall ink) is a purple-black or brown-black ink made from iron salts and tannic acids from vegetable sources. It was the standard writing and drawing ink in Europe, from about the 5th century to the 19th century, and remained in use well into the 20th century.
The ink was generally prepared by adding some iron(II) sulfate (FeSO4) to a solution of tannic acid (C6H2(OH)3COOH), but any iron ion donor (e.g. nails, iron metal scraps, etc.) can be used. The gallotannic acid was usually extracted from oak galls (also known as "oak apples"), or galls of other trees; hence the name. Fermentation or hydrolysis of the extract releases tannic acid, which yields a darker black ink.
The fermented extract was combined with the ferrous iron(II) sulfate. After filtering, the resulting pale-gray solution had a binder added to it, (most commonly gum arabic) and was used to write on paper or vellum. A well-prepared ink would gradually darken to an intense purplish black. The resulting marks would adhere firmly to the vellum or parchment, and (unlike india ink or other formulas) could not be erased by rubbing or washing. The marks could only by erased by actually scraping a thin layer off the writing surface.
By mixing tannin with iron sulfate, a water soluble ferrous tannate complex is formed. Because of its solubility, the ink is able to penetrate the paper surface, making it difficult to erase. When exposed to oxygen a ferric tannate pigment is formed. This complex is not water-soluble, contributing to its permanence as a writing ink.
The gradual darkening of the ink is due to the oxidation of the iron ions from ferrous (Fe2+) to ferric (Fe3+) state by atmospheric oxygen. (For that reason, the liquid ink had to be stored in a well-stoppered bottle, and often became unusable after a time.) The ferric ions react with the tannic acid or some derived compound (possibly gallic acid or pyrogallol) to form a polymeric organometallic compound. The specifics of the chemistry of iron gall ink can be found at realscience.com.
While a very effective ink, the formula was less than ideal. Iron gall ink is acidic ranging from roughly equivalent to a lemon (pH ˜ 2) to that of a cup of black coffee (pH ˜ 5). In chemistry, pH is a measure of the activity of the (solvated) hydrogen ion, where a lower pH level indicates a more acidic solution. For this reason some makers of iron gall ink used crushed egg shells (which contain calcium carbonate (CaCO3)) to temper the ink solution acidity, bringing it closer to a neutral pH (pH = 7) value. Depending on the writing surface being used iron gall ink can have unsightly "ghost writing" on the obverse face of the writing surface (most commonly vellum or paper.) Also any excess of ferrous ions remaining in the ink over years, decades, and centuries, could create a rusty halo around the marks and ultimately it might eat holes through the surface it was on.
Paper has its own special problems with iron gall ink. The iron-tannic pigment did not make chemical bonds with the cellulose fibers. The ink stuck firmly to the paper, but largely by mechanical bonding; namely, the dried ink penetrated the spaces between the fibers and, after drying, became entangled in them. The process of decaying the writing surface is accelerated on paper when compared to vellum, doing the damage in decades or years that could take more than a millennium on vellum.
The acidity of iron gall ink is well known but it must also be observed that the case for the acidity of iron gall ink is somewhat overstated. There are several thousands of manuscripts, some of them well over 1,000 years old, with iron gall ink on them that have no damage or degradation whatsoever from the iron gall ink. This understanding however should not be taken to ignore the potential issues of documents that use iron gall ink for the writing.
The earliest recipes on how to make oak gall ink come from Pliny the Elder and are vague at best. Many famous and important manuscripts have been written using ferrous oak gall ink including the Codex Sinaiticus the oldest most complete Bible currently known to exist thought to be written in the middle of the fourth century. Due to the ease of making iron gall ink and its quality of permanence and water resistance this ink became the favored ink for scribes in the European corridor as well as around the Mediterranean Sea. Surviving manuscripts from the Middle Ages as well as the Renaisance bear this out as the vast majority are written using iron gall ink the balance being written using lamp black or carbon black inks. Laws were enacted in Great Britain and France specifying the content iron gall ink for all royal and legal records to ensure permanence in this time period as well.
The popularity of iron gall ink traveled around the world during the colonization period and beyond. The United States Postal Service had its own official recipe that was to be used in all post office branches for the use of their customers. It was not until the invention of more chemically produced inks and writing fluids in the latter half of the 20th century that iron gall ink fell out of common use.
Edited by Abramelin, 20 April 2013 - 08:30 PM.