@EKWC - Glaze room

Glaze room
@ekwc
Sang de boeuf -
Reduction is an atmospheric condition in the kiln characterised by a shortage of oxygen. Reduction firing is used to achieve a colour change in the body and glaze. It is linked to the use of solid fuel and occurs when there is not sufficient oxygen present to combust the fuel. The main element found in the fuels like wood, oil and gas, is carbon. During combustion carbon combines with oxygen and is converted into carbon dioxide gas, provided sufficient oxygen is present in the atmosphere of the kiln. This gas escapes through the chimney. There are three kinds of atmosphere of the kiln during firing : oxidation; neutral, and reduction. If full combustion does not take place an unstable highly toxic carbon monoxide gas is formed. Unstable means that the carbon monoxide, is at it were, constantly searching for oxygen to form a more stable carbon dioxide gas. As a result all compounds present in a body or glaze that easily give up some of their oxygen will enter into a reduced state : their chemical composition is altered. This change in chemical composition can result in a change of colour of some colouring oxides.
Celadon -
La couleur bleu-vert du céladon provient d'une petite quantité d'oxyde de fer à l'état ferreux incluse dans la glaçure au moment de la cuisson en réduction (avec une entrée d'oxygène limitée). Une cuisson oxydante (avec une plus grande arrivée d'air) transforme le fer ferreux en fer ferrique (identique à celui contenu dans la rouille) et donne une couleur brun jaune à la glaçure. Il arrive que pendant le refroidissement, le four se réoxygène, et quelques vases présentent les deux couleurs.
, Copper metal, luster & Terra Sigilata -
(c) Chavanitas