TL;DR: To glaze and fire a porcelain vase, apply a thin, even coat of glaze by dipping or spraying, then fire it in a kiln to cone 6–10 (1222–1300°C) for a durable, glossy finish. Proper drying and slow cooling prevent cracks and glaze defects.
Step 1: Prepare the Bisque Vase
Start with a fully bisque-fired porcelain vase. Wipe away dust with a damp sponge. Ensure the surface is smooth and free of oils. If needed, sand rough spots with 400-grit wet sandpaper, then rinse and let dry completely.
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Step 2: Mix and Test the Glaze
Choose a glaze formulated for porcelain, such as a clear or celadon glaze. Stir thoroughly and sieve to remove lumps. Test on a small porcelain tile first to check color and fit. Adjust water content so the glaze coats like thin cream.
Step 3: Apply the Glaze
Dip the vase quickly and evenly, or spray in thin layers. For dipping, hold the vase upside down by the foot, submerge for 2–3 seconds, and lift smoothly. Wipe the foot ring clean with a damp sponge to prevent glaze from fusing the vase to the kiln shelf. Aim for a 1–2 mm thick coating.
Step 4: Dry and Load the Kiln
Let the glazed vase dry in a dust-free area for at least 12 hours. Place it on a kiln shelf with 1 cm clearance from other pieces. Use kiln stilts if needed, but never glaze the bottom. Program a slow ramp: 100°C/hour to 600°C, then 150°C/hour to the target cone.
Step 5: Fire and Cool
Fire to cone 6 (1222°C) for mid-range porcelain or cone 10 (1300°C) for high-fire. Soak at peak temperature for 10–15 minutes. Cool slowly—at least 8 hours—to prevent thermal shock. Do not open the kiln early.
Tips: Always test glaze compatibility. Keep notes on thickness and firing. If glaze runs, apply a thinner coat next time. For a matte finish, fire slightly cooler; for gloss, fire hotter.
FAQ
Q: Can I glaze a porcelain vase without a kiln?
A: No. Porcelain glaze requires high-temperature firing (cone 6–10) to melt and bond. Air-dry glazes or low-fire craft glazes will not achieve a durable, food-safe finish on porcelain.
Q: Why did my glaze bubble or pinhole?
A: Bubbles and pinholes usually come from applying glaze too thickly, firing too fast, or trapped dust. Apply thinner coats, sieve the glaze well, and hold the peak temperature longer to let bubbles escape.
Q: How do I prevent the vase from cracking during firing?
A: Dry the glazed vase completely before firing, ramp the temperature slowly (under 150°C/hour), and cool the kiln gradually. Thick walls or uneven glaze can also cause stress cracks.
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