How does elevation affect a Raku firing?

Elevation can have a significant impact on a Raku firing in a couple of areas - especially with a gas-fired kiln. First the higher the altitude the "lighter" the air, meaning there are less oxygen molecules in the same volume of air at high altitudes versus sea level. Hence it requires more "light" air to provide the same amount of oxygen to a firing kiln than normal air. This means you probably need a larger port opening and a large flue opening in your kiln to allow in more air. Second you probably need a smaller orifice (the little hole) in your burner so less fuel is mixed with the air. Now unfortunately the gas used to fire the kiln will more quickly expand in "lighter" air so it will not provide the same magnitude of firepower as slower expanding gas would provide. So this means it will take more time to get a kiln to temperature at higher elevation.

Having less oxygen in the air will make heavy reduction easier (both in the kiln and post-firing). So if you want a piece to be oxidized or lightly reduced you will likely need to let the piece cool more before it is placed in the reduction chamber.

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