What's Atmospheric Firing?
A lot of times people are curious about how different pieces are made, why are certain colors normal for certain firings, what techniques did the artists use, how was that form made etc.. Most of the time, folks are looking for some clue as to the process that the potter may have used to achieve the specific results in hopes that they can repeat them. I'm a big big fan of letting people know as much information as they could possibly want. I think that's how things progress. We stand on the shoulders of our forefathers to create the new and different - but first, we need to know how they did it. Hopefully, this blog will give you some helpful information and tips as to how things are made be it materials, process, or equipment. From there, it's on you to create the new and innovative. With my blessing.
How can you tell when a piece of ceramics has been wood fired?
Starting with the basics; kilns are ovens that heat clay until they go through a chemical and physical change making them hard. One type of kiln firing is something called “Atmospheric Firing”. This means that the atmosphere in the kiln is actually full of chemicals, minerals, etc. that will create glaze on the ceramic work (and everything else in the kiln) without having to actually apply a glaze to the pieces beforehand – think of it as an air-born glaze. There are three basic firing methods that do this;
Wood firing: Where wood is the kilns fuel and the minerals and metal oxides inherent in the tree attaches itself to the pot.
Soda firing: When soda is introduced into a hot kiln and the soda travels throughout the kiln to coat the ceramics present.
Salt firing: Same as soda - just has a different look and feel to it.
Wood firing is when you use wood as your kiln fuel and when the wood combusts it creates ash that’s full of various minerals, metal oxides, chemicals that will actually melt on the ceramics. To prevent the pieces from sticking to the kiln shelves during the firing, little balls of wadding (clay w/ additives) are placed on the shelves and pieces to separate them as they get coated with the wood ash glaze. Many times, and rather traditionally, sea shells were/are used on top of the wadding which leaves the sea shell pattern in the glaze and clay surface. These marks, with or without shells are typical indications of an atmospheric firing.