9.3.1: Reduction
- Page ID
- 299319
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)Val Cushing was a renowned American ceramic artist and educator, known for his contributions to ceramic techniques and glaze formulations. While Cushing explored various firing methods throughout his career, his approach to reduction firing is particularly noted for its ability to achieve rich, vibrant glaze results characteristic of reduced oxygen atmospheres.
Reduction firing is a technique used in ceramic kilns to create a specific atmospheric condition where the kiln atmosphere is made rich in fuel but poor in oxygen (reduction atmosphere) during certain stages of the firing. This atmosphere affects the colors, textures, and finishes of glazes and clay bodies.\
Here is a summary of a typical reduction firing technique inspired by practices similar to those Val Cushing might have used, described in both Fahrenheit and Celsius:
1. Bisque Firing: Before reduction firing, ware is bisque fired to prepare it for glazing. This is typically done in an oxidation atmosphere to around 1832°F (1000°C).
2. Glazing and Loading: After bisque firing and applying glazes, the ceramic pieces are loaded into a kiln. Care is taken to ensure good air circulation around each piece.
3. Ramp to Bisque Temperature: The kiln is slowly heated to the bisque temperature again, around 1832°F (1000°C), to ensure the glaze properly adheres to the surface.
4. Reduction Phase Initiation: Reduction is typically started at a temperature around 1652°F to 1724°F (900°C to 940°C) and is maintained or adjusted based on the specific glazes used and desired effects. The reduction atmosphere is achieved by adjusting the kiln's fuel-to-oxygen ratio, making the kiln atmosphere rich in carbon.
5. Soak at High Temperature: The kiln temperature is increased to the target high temperature, often around 2345°F (1285°C) for cone 10 firings, which is a common target for stoneware and porcelain. During this phase, the kiln is soaked (held at a constant temperature) to allow the glazes to mature fully.
6. Oxidation Phase: Near the end of the firing, the kiln atmosphere may be brought back to oxidation for a short period to help clear any residual carbon from the glazes and clay body. This might be around 200°F to 300°F (about 93°C to 149°C) below the peak temperature.
7. Cooling: The kiln is allowed to cool naturally. Rapid cooling can be employed for certain effects but requires careful control to avoid thermal shock.
8. Unloading: Once the kiln has cooled to room temperature, the ware is unloaded, and the results are evaluated.
Val Cushing’s specific firing schedules, glaze recipes, and techniques might vary based on the desired outcomes, the kiln type, and the glazes used. However, the essence of reduction firing revolves around controlling the atmosphere within the kiln to influence the final appearance of the ceramic pieces. Always refer to specific glaze recipes and firing schedules for best results, as these can vary widely.