TL;DR: To make porcelain vases, wedge high-fire porcelain clay into a smooth, air-free mass before centering it on a pottery wheel to pull up uniform walls. Finish the piece by trimming the foot, applying a translucent glaze, and bisque firing the greenware before glazing and firing to high temperatures for a glassy finish.
Step-by-Step Tutorial
Creating porcelain vases requires precision because the material is fragile and prone to cracking if mishandled. Begin by preparing your workspace with a clean, non-absorbent surface and ensure your potter’s wheel is perfectly balanced. Gather your tools, including a rib, sponge, loop tool, and cutting wire, to streamline the process and maintain efficiency throughout the creation phase.
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First, prepare the porcelain clay by wedging it thoroughly. This critical step removes air bubbles that can cause explosions during the firing process. Use the ram’s head wedging method to ensure the clay is plastic and uniform. Knead the clay until it feels smooth and consistent, then roll it into a ball and place it on the wheel head. Secure the clay firmly to the wheel using water and your hands to prevent slipping during the centering stage.
Center the clay by pressing down with both palms while the wheel spins at a medium speed. Use your thumbs to push the clay up from the center to create a mound, then press down again to flatten it. Repeat this process until the clay rotates without wobbling. Once centered, open the hole in the center using your thumbs, pulling down and slightly outward to form the initial cavity of the vase.
Begin pulling up the walls of the vase by wetting your hands and using a sponge to remove excess water. Place your fingers inside the clay and your thumbs on the outside, then gently pull upward in a smooth, continuous motion. Keep the walls even and consistent in thickness, aiming for a thickness of about six millimeters. Porcelain shrinks significantly, so account for this reduction by making the initial walls slightly thicker than desired.
Shape the rim and neck of the vase by adjusting the tension on the top edge. Use a rib tool to smooth the exterior surface, ensuring there are no ridges or imperfections that could weaken the structure. Trim the foot of the vase while the clay is leather-hard, using a loop tool to create a clean, flat bottom. This step is crucial for stability and aesthetic appeal, as it removes excess clay and defines the base of the vase.
Allow the vase to dry slowly and evenly to prevent cracking. Cover it with a damp cloth or plastic bag to control the drying rate. Once bone dry, apply a thin layer of clear glaze or a decorative glaze of your choice. Ensure the glaze does not touch the unglazed foot to prevent sticking to the kiln shelf. Bisque fire the piece at low temperatures, then glaze fire at high temperatures to achieve the characteristic white, translucent look of porcelain.
FAQ
Q: Why does porcelain crack during drying?
A: Cracking usually occurs due to uneven drying rates or trapped air bubbles. Ensure you wedge the clay thoroughly and dry the piece slowly using plastic or damp cloths to maintain consistent moisture levels throughout the structure.
Q: What temperature is needed to fire porcelain?
A: Porcelain requires high temperatures, typically between 1250 and 1300 degrees Celsius, to achieve full vitrification. This high heat fuses the clay particles into a dense, glass-like surface that is watertight and durable.
Q: How can I achieve a pure white color?
A: Use a high-quality porcelain body with low iron content and apply a clear glaze that is specifically formulated to remain white at high temperatures. Avoid glazes that contain iron or other metal oxides that may introduce yellow or gray tones during firing.
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