If you have read my earlier Blog post on “Painting on vellum’ you will know that the vellum on which I mainly paint is a type of calfskin vellum called ‘Kelmscott’ vellum. This is actually the heaviest of all the vellum as it is prepared in the usual way but also has a special plaster of Paris surface coating which creates extra depth and a particularly smooth ivory surface for painting or calligraphy.
One particular property of Kelmscott and some other vellums is a glowing luminous colour – just think of Medieval illuminated manuscripts. These were described as illuminated from the Latin ‘illuminare’ (to light up) which refers to both the gold and silver often used in the illustrations but also to the radiant colours of the pigments. These manuscripts on vellum are centuries old but most retain their sumptuous colour.
So how is the glow achieved? You might think there is something special in the paint but that is not the case. Watercolour paint and its predecessors has changed very little over the centuries . I am no expert in the composition of Medieval paint so I can only speak with any authority about my own experiments but I came to Botanical Art having previously worked in oils. While experimenting with oil painting I learnt about a technique involving underpainting with and over white in a neutral grey/brown (otherwise known as ‘Grisaille’ or ‘Brunaille’) topped with glazes of transparent paint. Light travels down through the transparent oil glazes, bounces off the white and travels back out of the painting, creating a luminous glow that seems to light the painting from within.
Here’s how it looks on oils with a dark background. Intriguingly the painting glows more the more the lights are lowered.
When I started painting in watercolour on vellum I realised that the same technique works, with some adjustment, on vellum. Vellum is semi-opaque unlike paper; something dark held behind a piece of vellum is clearly visible. Conversely white paper behind vellum will help bounce light back out. I always ensure that my vellum pieces are framed with acid-free white paper behind it to allow the light to travel back out. The main trick, however, is the transparency of the paint. In the parts of a painting that I want to glow I ensure I use transparent or semi- transparent paint and in those parts that I want colour to be more muted I will use paint that is more opaque.
Coming up soon – using Dramatic Darks on Vellum.