1. Shrinkage glaze
Features: The glazed surface is uneven with inward concave blocks.
Reason: the glaze shrinks too much when it is dry; Too fine glaze particles: too thick glaze layer.
smoke
Features: Some or all ceramic products are gray-black-brown.
Reasons: the humidity in the kiln is high and the fuel combustion is insufficient, which leads to the bad body absorbing smoke and dust; The carbon in the bad body (including the decomposition products of organic matter in the green body and the smoke absorbed by the bad body in the kiln) is not fully oxidized; The kiln is too dense and the smoke exhaust power is insufficient, resulting in smoke in the kiln.
3. Deformation
Features: porcelain does not conform to the design shape, such as the edge is not round and drooping, improper covering, etc.
Cause: Repair problem: the temperature difference in the kiln is large or the temperature rises too fast and the temperature is too high during firing.
4. Fetal fissure
Features: The porcelain matrix is cracked.
Reason: The moisture content of the bad blank is too high when it enters the kiln, and the preheating and cooling are too fast, which leads to uneven shrinkage and cracking of the blank.
5. Ore occurrence
Features: Black or brown spots appear on the surface of porcelain, also known as iron spots and black spots.
Reason: It mainly comes from iron, carbon and other elements in tires and glazes.
Accumulated material
Features: Painted porcelain has bulges or the color is too heavy and dark, which is more common in glazed red or blue and white porcelain. Some people who copy ancient porcelain of Yuan and Ming dynasties will copy it deliberately.
Reason: In the process of drawing, color materials are used too much.
Step 7 drop slag
Features: Also called dirty, it means that the surface of the product is stuck with dregs such as chaff ash.
Cause: (1) The bowl and mortar are placed smoothly or the track is uneven when loading, and excessive force causes the sagger to shake or the slag particles that are shaken when pushing the kiln car.
(2) Slags fall into the blank due to improper handling when the blank or kiln is overlapped with the box.
8. Glaze cracks
Features: the glaze is cracked and has fine lines.
Cause: Most of them are caused by uneven heating.
9. spike
Features: the surface of porcelain is uneven and feels prickly.
Reason: the pigment is not polished carefully enough; Overglaze color.
10. Dirty color
Features: There are many points on the surface of porcelain without patterns.
Reason: the painter's mistakes in the process of drawing.
1 1. Glaze bubble
Features: There are small bubbles on the glaze.
Cause: The firing temperature is too high or too low, which makes it difficult for bubbles to be discharged and stay.
12. Blank bubble.
Features: hollow bubbles protruding from the underglaze color body.
Cause: There are too many organic matter and carbonate in the mud, and the oxidation is insufficient.
13. Thickness of decorative glaze
Features: the pattern of glaze covering the carcass.
Reason: too much glaze.
14. Slag sticking at the bottom edge
Features: Fine slag particles stick to the edge of product feet.
Reason: Before loading, the slag particles in the box were not emptied, and the bran ash, alumina powder and quartz powder scattered on the bottom of sagger and pad cake were too thick or uneven, resulting in slag sticking; When scraping the glaze from the bottom foot or mouth edge of the blank, the amount is too small or not clean, which makes the glaze at the bottom foot of the bad blank stick to powder and chaff ash.
15. Material cutting
Features: The painted lines on the porcelain surface are broken.
Reason: In the process of painting, the line drawn by the painter was broken.
16. Uneven glaze
Features: You can obviously feel the thickness when touching porcelain.
Reason: I didn't master the thickness when glazing.
Glaze crack
Features: the glaze is cracked and has fine lines. Cause: Most of them are caused by uneven heating.