Note 15: OAK GALLS - walks, wills, and wingless wasps
Country walks are a daily requirement for me. With an energetic dog and a wife who spends all day painting in a studio, the beautiful countryside that makes up the Cotswolds is always a wonderful destination to visit, if only for a short walk. Come rain or shine we’ll be out, and in the dark winter evenings, woodland walks by torchlight are always fun. We have a pile of OS maps covering the area (as well as the south coast and other holiday destinations) and always like to find new circular walks which are then marked with a pen on the map and the duration written down too.
Last weekend's walk took us just south of Bourton on the Water, that popular tourist destination sometimes referred to as Venice of the Cotswolds, with five bridges spanning the shallow River Windrush.
As a gardener my eyes are always peeled for plants of interest, trees, and natural history subjects. On this walk a row of recently planted oak trees caught my eye and I immediately spotted something I’d been looking out for over the last twelve months - oak apples, or oak galls as they are also known: perfectly smooth, spherical balls attached to the tree's branch at eye level. I plucked off half a dozen and put them in my pocket. I had plans in store for these lightweight, sun baked ‘marbles’.
Oak apples are formed when a small wingless female wasp (Biorhiza pallida) crawls up the trunk of an oak tree and lays eggs in the undeveloped buds. At the same time she introduces a venom that causes the tissue in the bud to soften and swell. When the larvae hatch they introduce further chemicals that cause the bud to create the round, initially spongey ball that we know as an oak apple. After about 3 months the larvae develop into adult winged wasps and leave the gall through a small hole. Eventually the gall dries out and falls to the floor.
Back home the galls remained in my pocket for a week before I started on my project. I was going to make iron gall ink, an ink used for writing for at least 2000 years. Waterproof, permanent, and with few alternatives the ink has been used to create many important documents including Shakespeare's 1616 last will and testament, the 13th century Magna Carta, 4th century Codex Vaticanus, and the 1776 Declaration of Independence.
In the kitchen I crushed the galls using a pestle and mortar and mixed the resultant powder with some rainwater. It stayed like this for a couple of days during which time the tannins leached out into the liquid. I then added some iron sulphate left over from a garden lawn project. This addition reacted with the tannins to produce a dark brown, almost black liquid to which I added gum arabic to improve the viscosity and finally some clove oil which not only improved the smell but guarded against mould forming.
The final test was to write with this ink. Initially it was too thin so I evaporated some of the water off in the microwave and produced a liquid that produced a great ink in a subtle antique brown that I applied using a cheap calligraphy pen. More adventurous writers could try a quill for the perfect retro experience.
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