GB/T 21998-2008Product of geographical indication - Dehua white porcelain (English PDF)

1 Scope

This standard specifies the terms and definitions, the protected area of the geographical indication product, the product classification, the requirements, the test methods, the inspection rules and the marking, packaging, transport and storage of Dehua white porcelain.

This standard applies to the Dehua white porcelain placed under protection by the national administrative authority for quality supervision, inspection and quarantine in accordance with the Provisions on the Protection of Products of Geographical Indication.

3 Terms and definitions

The terms and definitions established in GB/T 3303 and GB/T 5000 and the following apply to this standard.

3.1 Dehua white porcelain: sculptural white porcelain and white tableware, pure white, fine and translucent in character, produced within the area of Clause 4 from high-silica, low-iron, low-titanium high-quality kaolin sourced within the administrative area of Dehua County as the main raw material.

3.2 seam mark: the trace of a mould joint showing on the surface of the product.

3.3 browning mark: the dark brown glazed surface left on the product after firing by a knot in the peeled wood, also known as a peeling mark.

3.4 blur of blue and white pigment: blue and white pigment whose colour is indistinct.

3.5 rough on blue and white pigment: blue and white pigment that feels rough to the touch.

4 Protected area of the geographical indication product

The protected area of Dehua white porcelain is limited to the area approved for protection by the national administrative authority for quality supervision, inspection and quarantine under the Provisions on the Protection of Products of Geographical Indication, namely the present administrative area of Dehua County, Fujian Province, as shown in Annex A.

5 Product classification

5.1 By use, products are divided into sculptural white porcelain and white tableware. 5.1.1 Sculptural white porcelain is divided into figures, birds and animals, flowers and landscapes, and other sculptural pieces. 5.1.2 White tableware is divided into plates and dishes, bowls, pots, cups and other vessels.

5.2 By appearance quality, products are divided into superior, first, second and qualified grade.

5.3 By size, products are divided into small, medium, large and extra-large, the ranges being given in Table 1. For sculptural figures the four classes run from 50 mm up to but not including 150 mm, from 150 mm up to but not including 350 mm, from 350 mm up to but not including 550 mm, and from 550 mm to 800 mm; for birds and animals, flowers and landscapes and other sculptural pieces they run from 50 mm up to but not including 150 mm, from 150 mm up to but not including 250 mm, from 250 mm up to but not including 400 mm, and from 400 mm to 800 mm; sizes are taken on the largest external dimension of the piece. For tableware, plates and dishes are classed by rim diameter below 128 mm, from 128 mm up to but not including 228 mm, from 228 mm to 350 mm, and above 350 mm; bowls by rim diameter below 110 mm, from 110 mm up to but not including 175 mm, from 175 mm to 250 mm, and above 250 mm; pots by capacity below 250 mL, from 250 mL up to but not including 1 000 mL, from 1 000 mL to 2 400 mL, and above 2 400 mL; and cups by rim diameter below 60 mm, from 60 mm up to but not including 100 mm, and 100 mm and above, with no extra-large class. Other pieces are classed by analogy with the shapes above.

6.1 Body clay

6.1.1 The kaolin used as the main raw material of the body clay shall be high-quality kaolin sourced within the administrative area of Dehua County and having a high silica, low iron and low titanium character. Table 2 sets its chemical composition in per cent: silicon dioxide not more than 68.0; aluminium oxide not less than 18.0; potassium oxide not less than 1.5; sodium oxide not less than 0.5; calcium oxide not more than 0.4; magnesium oxide not more than 0.2; iron oxide not more than 0.5; titanium dioxide not more than 0.1.

6.1.2 The kaolin is prepared by pounding and washing, while the other constituents, porcelain stone, feldspar and quartz, are crushed and ball-milled; the whole is then sieved, de-ironed and aged to form the body clay.

6.1.3 The quality of the body clay is fixed as follows. Its appearance shall be uniform and fine in texture with no visible impurities. Its moisture shall be not more than 26 per cent. Its fineness shall give a residue on a 250-mesh sieve of less than 0.5 per cent. Its plasticity index shall be greater than 2.5. Its chemical composition shall comply with Table 3, in per cent: silicon dioxide not more than 73; aluminium oxide not less than 18; potassium oxide plus sodium oxide not less than 3.5; calcium oxide plus magnesium oxide not more than 0.8; iron oxide not more than 0.3; titanium dioxide not more than 0.1; loss on ignition not more than 4.

6.2 Production process

6.2.1 The production of Dehua white porcelain shall follow the process flow of Figure 1.

6.2.2 Forming. Sculptural white porcelain is formed by hand, by pinching, modelling, carving, incising, scraping, paring, joining and applying, or by slip casting. White tableware is formed, according to the shape of the piece, by hand, by machine, by slip casting or by isostatic pressing.

6.2.3 Surface decoration is divided into incised decoration, relief and painted decoration. In choosing the method, the pattern, the extent of the composition, the mood created and the brushwork and colouring, the character of Dehua white porcelain shall be brought out, so that decoration and material form a single whole and set each other off.

6.2.4 Glazing. Sculptural white porcelain is either glazed or left as biscuit; glazed pieces are dipped, poured, sprayed or brushed, with an appropriate glaze thickness. White tableware is glazed, according to the shape of the piece, by swilling, dipping, pouring or spraying, with an even glaze thickness.

6.2.5 Firing. Single firing is carried out at a high temperature of 1 250 degrees C to 1 400 degrees C. Double firing uses either a low-temperature biscuit firing at 800 degrees C to 900 degrees C or a high-temperature biscuit firing at 1 250 degrees C to 1 400 degrees C, followed by a high-temperature glaze firing at 1 250 degrees C to 1 400 degrees C. Decorating firing is carried out at 700 degrees C to 800 degrees C.

6.3 Product quality

6.3.1 Water absorption shall be not more than 0.5 per cent.

6.3.2 Whiteness shall be not less than 80.0.

6.3.3 The gloss of the glazed surface, matt glazes excepted, and the colour difference between the pieces of a set shall comply with Table 4. Table 4 fixes a minimum gloss value and a maximum colour difference, expressed as delta E, for each of the four appearance grades, but the OCR of the table does not attach the values to the grades unambiguously, so they are not reproduced here.

6.3.4 Further requirements for white tableware. Thermal shock resistance: small and medium pieces shall not crack after one exchange from 180 degrees C to 20 degrees C, and large and extra-large pieces shall not crack after one exchange from 160 degrees C to 20 degrees C. The release of lead and cadmium shall comply with GB 12651. The lid of a covered piece shall broadly match the mouth; a pot tilted through 70 degrees shall not lose its lid, the gap between lid and pot mouth when the lid is moved to one side shall not exceed 3.0 mm, and the opening of the spout shall not be lower than the pot mouth by more than 3.0 mm.

6.3.5 Tolerances on size. For sculptural white porcelain, plus or minus 3 per cent for small and medium pieces and plus or minus 2 per cent for large and extra-large pieces. For white tableware, the tolerance on rim diameter is plus or minus 2.0 per cent for a rim diameter below 60 mm and plus or minus 1.5 per cent for a rim diameter of 60 mm and above; the tolerance on height is plus or minus 3.0 per cent; and the tolerance on mass is plus or minus 6.0 per cent.

6.3.6 Appearance quality. Sculptural white porcelain shall be pure white, fine and elegant, translucent, with clear, slender and flowing lines, deep and rounded carving, and drapery pared thin at the folds so that it appears light and lifting. White tableware shall be pure white, fine and warm, translucent, with a clear thick glaze. Superior and first grade pieces shall stand steady on a flat surface, and second and qualified grade pieces shall stand broadly steady. Marks on the base, meaning trademarks and lettering, shall be correct and clear and shall not be visibly skewed or off-centre. The pieces of a set shall be broadly consistent in colour and proportionate in size, and sculptural pieces made in batches shall be consistent in the depth of the carving and in the size of hands and feet, with fittings and ornaments of uniform size.

6.3.6.5 Defects on the exposed parts of sculptural pieces. No defect is permitted on the front-facing part of the face of a figure. Spots, adhering grit, melt holes, lumps, body blisters, clay debris, pinholes, missing clay, missing glaze, plaster staining and similar defects on the parts of the face not seen from the front, on the crown of the head, the white beard and hair, the chest, abdomen and limbs of a figure, and on the head and feet of birds and animals, are governed by Table 5; Table 5 tightens or relaxes the permitted size and number of defects by grade and by the size class of the piece, and the OCR of the table does not allow each allowance to be tied to its cell with certainty. Spot defects on the exposed crown of the head of luohan, longevity gods and similar pieces are not permitted at superior and first grade; for small and medium pieces, second and qualified grades allow one such spot of not more than 0.5 mm, and for large and extra-large pieces second grade allows one and qualified grade two. Cracks on exposed parts are not permitted at superior and first grade; for second and qualified grade, a hairline crack of not more than 5 mm at one place is allowed on a small piece, not more than 10 mm on a medium piece, not more than 15 mm on a large piece and not more than 20 mm on an extra-large piece, no crack running through both body and glaze is permitted on a visible face, and cracks on a non-visible face are reduced by 50 per cent against the allowances of Table 6.

6.3.6.6 Other appearance defects shall comply with Table 6, and in addition a superior grade piece shall not carry more than 2 kinds of defect, a first grade piece not more than 3 kinds, a second grade piece not more than 4 kinds and a qualified grade piece not more than 5 kinds. Table 6 is the long grading table of the standard: it lists thirty-four named defects, from warping, adhering grit, pinholes, spots, colour staining, sticking scars, melt holes and plaster staining through slip marks, seam marks, lumps and body blisters, clay debris, glaze bubbles, missing glaze, browning marks and cracks to grit on the foot rim and base, water-blistered and burred rims, glaze sticking from the decorating firing, missing clay, faults in drawn lines, off-colour blue, gold and enamels, faults in the painted panel, fire spots, smoke staining and yellowing, thin or orange-peel glaze, skewed spouts, handles and lugs, glaze and clay streaks, scratched glaze, shrunken pigment, and chips, glaze bursts, cracks through the wall and leaks. For each defect it sets the unit of measurement, distinguishes small, medium, large and extra-large pieces, and states for each of the four grades what size, area, volume, length or number is allowed, generally distinguishing visible from non-visible faces. Because the columns of Table 6 are broken up by the OCR, the individual allowances are not reproduced here. The notes to the table do state the conversion rules: unless otherwise stated the allowances apply to visible faces, and the stated dimensions may be increased by 50 per cent on non-visible faces, with pinhole sizes unchanged and two pinholes counted as one; where a defect is smaller than half the stated size and slightly more numerous than allowed, two may be counted as one, provided the absolute increase does not exceed 50 per cent of the total permitted for the grade; where no limit on the number of places or pieces is given, sizes may be added together; for first, second and qualified grade, faint defects not more than 0.3 mm in diameter, not more than 0.5 mm in length or not more than 1.0 square millimetre in area, and other inconspicuous defects, need not be counted; no more than two defects are permitted within 10 square millimetres; on the undecorated parts of sculptural pieces the allowances and counts of Table 6 are reduced by 50 per cent for small, medium and large pieces, while non-visible faces keep the stated figures; for second and qualified grade pieces only, the visible interior space of vessels whose main feature is sculptural, and small toys and small practical sundries, may be graded with the Table 6 allowances increased by 50 per cent; and a defect not covered by the standard is treated as the most similar listed defect.

7 Test methods

Water absorption is determined in accordance with GB/T 3299. Whiteness and colour difference are determined in accordance with QB/T 1503. Gloss is determined in accordance with GB/T 3295. Thermal shock resistance is determined in accordance with GB/T 3298. The release of lead and cadmium is determined in accordance with GB/T 3534. Deformation is determined in accordance with GB/T 3300. The tolerances on size and the dimensions of defects are determined in accordance with GB/T 3301.

8 Inspection rules

8.1 Product inspection is divided into delivery inspection and type inspection, carried out as an inspection by number of nonconforming items per hundred units.

8.2 Delivery inspection. Every piece shall be inspected in full by the inspection department of the manufacturer and shall pass delivery inspection before leaving the works, accompanied by a document or mark certifying conformity. The delivery inspection items are those of 6.3.4.3, 6.3.5 and 6.3.6, and further technical requirements may be added as needed. Delivery inspection follows GB/T 2828.1. Table 7 classifies all three items as class B nonconformities with an acceptance quality limit of 4.0, and applies general inspection level II to 6.3.4.3 and 6.3.6 and special inspection level S3 to 6.3.5, with single sampling starting from normal inspection and following the switching rules. Table 8 then gives the sample size and the acceptance and rejection numbers for each lot size range under general inspection level II and special inspection level S3; the columns of that table also carry an acceptance quality limit of 2.5 that is not among the values used in Table 7, and the OCR of the table does not allow its figures to be tied to their columns with certainty, so they are not reproduced here. Where the sample size equals or exceeds the lot size, 100 per cent inspection is carried out. Lots may be formed by single piece, set, grade, decoration or shape, and subdivided if necessary. Samples are drawn at random, sets being converted into single pieces first. If any one delivery inspection item fails, the product is judged nonconforming, and the batch may be resubmitted only after rework by the consignor.

8.3 Type inspection. Type inspection covers all the technical requirements of the standard; the release of lead and cadmium and thermal shock resistance shall be tested at least once a quarter and the other items at least once every six months. Type inspection shall also be carried out when the raw materials change; when a change in the production process may affect product performance; when production resumes after a stoppage of more than six months; when an unforeseen incident occurs in production; when the delivery inspection results differ appreciably from the previous type inspection; and when the higher-level quality supervision body calls for it. Samples for type inspection shall be drawn from one or more batches manufactured within the stated period and already passed as batches, and shall be drawn in a way that makes them representative of the manufacturing standard of the period, preferably by taking sample units spread across different times within it. Type inspection follows GB/T 2829. Table 9 sets, for each inspected item, the nonconformity class, the rejection quality level, the discrimination level, the sampling plan, whether single or double, and the sample size with its acceptance and rejection numbers; the OCR of the table does not allow those figures to be attached to their items with certainty, so they are not reproduced here. If any one item fails, the product fails type inspection.

9 Marking, packaging, transport and storage

9.1 The special mark for products of geographical indication shall be applied to the product or its packaging. The packaging shall carry the product name, size, number of pieces in the set, quality grade, manufacturer's name and address and the product standard number, together with the words or symbols for fragile and for keep dry.

9.2 Packaging, transport and storage shall follow GB/T 11423.