October 6, 2023

The Tradition and Technique of Salt Glazing

Discover the distinctive salt glazing pottery technique. Learn how salt vapor in the kiln interacts with clay and glaze to create unique pebbly textures.

Salt glazing pottery

Salt glazing is an ancient atmospheric pottery technique. The method involves introducing common salt into the kiln, which leads to "orange peel" glaze effects. Mastering salt glazing requires precise timing and technique. Let's delve into this fascinating tradition.

Understanding Salt Glazing

Salt glazing is a pottery decoration process where sodium chloride, ordinary table salt, is introduced into the kiln during the firing process. As the salt is heated, it vaporizes, creating a salty atmosphere that reacts with the clay and glaze. This interaction produces the distinctive orange peel textures and crater-like markings that define salt-glazed pottery.

This technique is only applicable in high-fire gas or wood-fired kilns that can reach temperatures over 2300°F. The superheated, salt-infused atmosphere adds unparalleled depth and vibrancy to the pottery.

Historical Origins of Salt Glazing

The practice of salt glazing has its roots in ancient Germany, where it was used primarily as a functional technique. Its advantages include:

  • Salt glaze forms a water-resistant coating, enabling storage jars to resist liquids.
  • The pebbly texture conceals imperfections in hand-thrown pieces.
  • The use of common kitchen salt made it an affordable and easily available material.
  • The proximity of kilns to the salt sources allowed for easy firing.

Today, the tradition of salt glazing is cherished more for its aesthetic appeal and historical significance than its practical function.

The Science Behind Salt Glazing

The characteristic effects of salt glazing are a result of several chemical reactions:

  • Salt vaporizes and dissociates into sodium and chlorine gases.
  • Sodium reacts with the silica present in clay and glaze, forming a glassy coating.
  • The chlorine gas produces tiny bubbles that result in a cratered, pebbled texture.
  • Iron in the clay leads to the distinctive orange peel coloring.

Mastering the timing and scheduling of these reactions is crucial to achieving the desired effects.

Mastering the Salt Glazing Process

Executing the salt glazing process necessitates a precise sequence for successful results:

  • Load the kiln and fire steadily up to 2200°F.
  • Apply an initial coat of glaze and allow it to set for 15-20 minutes.
  • Swiftly open the peepholes and introduce the first batches of salt.
  • Continue the process of salt throwing every 5-10 minutes until the kiln reaches 2350°F.
  • Cease the addition of salt, but maintain the kiln at the top temperature.
  • Close the peepholes and increase the damper draft for a quicker cool down.
  • Once the kiln temperature drops to 1000°F, plug all openings to prevent re-oxidation.

For the unique effects to materialize, the rapidly volatilizing salt must interact with the melted glaze.

Tips for Successful Salt Glazing

For optimal salt glazing results, consider these recommendations:

  • Use a high-temperature stoneware or porcelain clay body.
  • Ensure there are sufficient peepholes to introduce salt without causing significant heat loss.
  • Load the kiln lightly to allow for proper heat circulation and salt penetration.
  • Opt for coarser rock salt, which provides more surface area than table salt.
  • Time the salt throwing to coincide with the liquefaction of the glaze to enable reactions.
  • Always wear safety gear, as the vapors produced are highly corrosive.

Mastering salt glazing requires careful timing and practice, but the reward is exquisite pottery with a richness and depth that's truly unparalleled.

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