Reduction Road


Reduc­tion (adjec­tive) refers to a kiln atmos­phere which does not have enough oxy­gen in it to com­pletely con­sume the fuel as it burns. Due to this defi­ciency, the flame pulls oxy­gen mol­e­cules out of the clay bod­ies and glazes, chang­ing their char­ac­ter. Reduc­tion can be also be used to describe clay bod­ies and glazes that are espe­cially devel­oped for reduc­ing atmospheres.

Reduc­tion (noun) refers to the state of being oxygen-starved. It can also be used to replace the full term, “reduc­tion atmosphere”.


Reduc­tion fir­ing means that part of the fir­ing cycle is con­ducted with an inad­e­quate amount of air and oxy­gen to burn up all the fuel. As a result, the free car­bon in the air unites with, and thus reduces, the oxy­gen con­tent of the metal­lic osices in both the body and the glaze, thereby alter­ing their color.

How to Put a Kiln in Reduction


reduction coneTo put your kiln in reduc­tion, gen­er­ally, start the reduc­tion cycle when the wit­ness cone before your tar­get cone begins to tip. For exam­ple, with a cone pack with cones four, five, and six (the tar­get cone being cone five), you will want to start reduc­tion when cone 4 starts to tip.

You want to build up some pres­sure in the kiln. Par­tially close dampers in the chim­ney or reduce the open­ing in the exit hole (depend­ing on your kiln’s design).

Reduce the amount of air being drawn into the kiln — either slow blow­ers down, decrease the air open­ing in a ven­turi burner, or stuff a bit of ceramic fiber or fiber blan­ket into the port opening.

How Do You Know It Is in Reduction?

You can tell your kiln is in reduc­tion when any open­ings (such as updraft exit flues or open peep holes) have yel­low to orange flames com­ing out. Green or blue flames (or no flames, after wait­ing for the pres­sure to pop them out) means the kiln is not in reduc­tion yet. The fur­ther the flame reaches out­ward, the stronger the reduc­tion is. When using ven­turi burn­ers, with expe­ri­ence you may also be able to tell the strength of the reduc­tion by the whis­tle of the air going through the burner.

Com­plet­ing the Reduc­tion Cycle

Once the kiln has reached tem­per­a­ture and the amount of reduc­tion time as desired, shut down the burn­ers and any blow­ers. Close the dampers or cover the exit flue com­pletely. Put plugs in any open peep holes, and if the kiln is small, close off the burner port holes with either ceramic fiber blan­ket or small pieces of firebrick.

The kiln does not have to be air-tight, but it should be shut off from most air-flow. (If the damper / flue is com­pletely closed and all peep holes into the stack area are plugged, the pres­sure in the kiln will keep air from enter­ing the port holes, as long as the kiln is large enough and the burner ports are not too large.

Explore a Dif­fer­ent Street

Artists on Reduc­tion Road

55. Linda Bourne
56. James De Rosso
57.Jill War­ila
58. Geri Lynn Enos
59. Linda Workamn-Morelli
60.Sandy Brown
61. Stan Gib­son
62. Alissa Clark
63. Ken Pin­cus
64. Julie Asburry
65. Gail Pen­der­grass
66. Tra­cie Manso
67. Hsin-Yi Huang
68. Lynn Town­son
69. Chris McClel­land
70. Nao Tojim­bara Tijiri
71. Anthony Gor­don
72. Eliz­a­beth Sul­li­van
73. Jeff Gunn
74. Pat Berman
qr code