Walnut ink is a botanical ink made from the green (and then browning) husks around walnuts; not the actual walnuts or walnut shells themselves. When cooked up in water they give the most incredible dark brown colour, which has been used for ink in recent times and is particularly favoured by modern calligraphers, and especially adored by vegans as my version does not include shellac.
It might be tempting to assume that walnut ink has been used for centuries, certainly the sepia toned writings and drawings of artists like Leonardo Da Vinci might lead your to believe that this is what he would have used. However, surprisingly there is little evidence that any of the Grand Masters, medieval monks, or indeed ancient peoples ever used walnut ink as an ink of choice. Rather they used a 'black' ink made made from oak galls (stand by for my version to come to my shop soon!). This ink over the centuries faded to the brown colour that is visually what we can achieve with walnut ink today.
Walnut ink is perfect for calligraphers, and use with dip pens - although you should be careful to always wash your pens carefully afterwards as the ink is a little acidic. As it is a water-based ink, it can be used as a paint, a wash, or in watercolours. It can also be used to give an aged look to paper. The earth tones look wonderful when used for printing or stamping too either on fabric or on paper.
I hope you've enjoyed learning a little about walnut ink if you hadn't come across it before. It is a wonderful and versatile ink with wonderful nostalgic sepia tones.
You can purchase it here in my store.