The pots with crackle glaze They offer a unique and timeless aesthetic that makes them valuable pieces in the art of bonsai. Below, we explain the technical process for creating pots with this finish, from the specific materials to the temperatures and cooking times required to achieve the crackle finish.

What is crackle glaze? components and formula

Craquelure is the fissure or crack effect that appears on the surface of a glaze when it contracts as it cools. This phenomenon occurs due to differences in thermal expansion between the glaze and the base clay. To achieve this, it is important to select specific components that have a different coefficient of thermal expansion than the clay.

• Key components of a crackle glaze:
  • Silica (SiO₂): An essential component that provides durability and shine. Silica should have a concentration between 60-70%, as this will allow for greater contraction of the enamel when it cools.
  • Alumina (Al₂O₃): Added in small quantities (between 5-10%), this component helps to improve the hardness and resistance of the enamel.
  • Sodium Oxide (Na₂O) and Potassium Oxide (K₂O): Both are fluxing components that lower the melting point of the enamel and increase its fluidity, allowing for better distribution on the surface. They are used in concentrations between 5-15%.
  • Borax (B₂O₃): This mineral promotes thermal expansion and is essential to obtain the crackle effect. A concentration of 2-8% is ideal for the enamel to have the elasticity necessary to create the cracks.

The balance between these components is essential to achieve a crackle glaze that is stable, attractive and durable. Tests are often carried out on small samples to fine-tune the glaze formula before applying it to the final pots.

Preparation process and cooking temperatures

1. Selecting the clay and modeling the pot
   • The ideal clay for these pots usually has a low coefficient of thermal expansion. This allows the glaze to contract visibly without fracturing the piece.
   • The piece is modeled on a lathe or by hand and then left to dry until it reaches a moisture content of less than 5%, which prevents deformations and cracks during firing.
2. First firing or Bisque Firing
   • Temperature: Between 900-1000°C. This temperature range hardens the clay without completely vitrifying it.
   • Cooling Duration and Speed: This firing should last approximately 8 hours, and cooling should be slow (between 2-4 hours) to avoid thermal shocks. This step hardens the piece and prepares it to receive the glaze without deformations.
3. Application of crackle glaze
   • After the first firing, the piece is cleaned to remove any dust and the crackle glaze is dipped or sprayed onto the surface. This step requires precision to ensure an even layer that produces a homogeneous crackle.
4. Second firing to activate the crackle
   • Temperature: The second firing must reach between 1200-1250°C. This high temperature allows the glaze to melt completely and begin to contract in the cooling process.
   • Cooling duration and speed: Firing can last between 10-12 hours, and cooling must be done at a controlled rate so that the glaze contracts without cracking the piece. A cooling period of about 4 hours is ideal to allow the glaze to create visible cracks without weakening the structure.
5. Final cooling and crackle setting
   • For a perfect finish, cooling can be slightly accelerated in the last 200°C to intensify the crackling. This is achieved by controlling the oven ventilation in a range of 100-150°C per hour.
   • Once cooled, the pot is inspected to ensure that the crack pattern is consistent and attractive.

Considerations for crackle and final finish

The crackle pattern can vary depending on several factors:

• Type and thickness of enamel: A thicker glaze tends to produce finer and more abundant crackles.
• Cooling Rate: A rapid cooling rate increases the number and size of cracks.
• Oven Temperature Settings: Small adjustments in the last 200°C can influence the density of the crackle, allowing each piece to have a unique finish.

Advantages of crackle glaze bonsai pots

Crackle glaze bonsai pots are the ideal choice for those looking for a refined and long-lasting aesthetic:

• Strength and Stability: High-temperature fired clay, together with crackle glaze, creates a piece that is resistant to both wear and tear and climatic changes.
• Unique Pattern: Craquelure cannot be reproduced identically, making each pot a unique piece.
• Aesthetic Complement: Crackle provides an antique and rustic appearance, adding visual depth and sophistication to the bonsai assembly.

At our pots section You can find a wide range of crackle pots. If you can't find what you're looking for, you can contact us via WhatsApp at 681 37 23 43