  The powdery nature and high alkali content of vegetable ashes make them ideal
raw materials to be used as modifiers of silicate compositions (glasses,
enamels and ceramics). Their utilisation since ancient times is described in
the literature of the history of glasses, but studies on the analyses of their
composition are still limited. We discuss here the compositions of tree and
shrub ashes (wattle, hawthorn, oak, green oak, olive wood, elm, poplar, apple
tree, vine shoot), of plants (carex, fern, dogwood), of cereals (wheat, maize,
rice), threshing waste and hay, mainly harvested in Maconnais, near Taiz\'e
(Sa\^one-et-Loire, France), by the potter Brother D. de Montmolin. The
contributions in alkali modifiers (Na2O, K2O), alkaline-earth (CaO, MgO) and in
silica are discussed in view of the data gathered from the literature of the
history of techniques used in the production of ceramics, enamels and glasses.
The huge variation in composition is usually attributed to recycling and is
questioned by the very broad range of compositions that we obtained in the
analyses of the ashes.
