Vitreous China

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China

China is type of sedimentary or residual clay. They are free from iron (hence can be fired to a white pure colour) and free from alkalis (hence highly refractory).

Obtained as a result of weathering of granite (containing alkali feldspar):

K2O.Al2O3.6SiO2 + CO2 + 2H2O ----> Al2O3. 2SiO2. 2H2O + 4SiO2 + K2CO3

Definition

SS 42: 1971 or BS 3402: 1969 determine vitreous china as sanitary ware material:

Vitreous china is a strong high grade ceramic ware used for sanitary appliances and made from a mixture of white burning clays and finely-ground minerals which, after firing at a high temperature and when unglazed does not have a mean value greater than 0.5% of the dry weight. It is coated on all exposed surfaces with and impervious non-crazing vitreous glaze giving a white or coloured finish.

Water Absorption

Test method to SS 42: 1971 or BS 3402: 1969 appendix A

None of the individual values of water absorption shall exceed 0.75% and the arithmetical mean of the values shall not exceed 0.50%.

Crazing Resistance

Test method to SS 42: 1971 or BS 3402: 1969 appendix B

None of the test pieces shall show crazing

Chemical Resistance

Test method to SS 42: 1971 or BS 3402: 1969 appendix C

None of the test pieces shall appear to the unaided eye of a trained observer to have suffered any loss of reflectivity on the glaze when compared to the control sample.

Chemical solution to be used: acetic acid, citric acid, detergent, hydrochloric acid, sodium hydroxide, sodium stearate, sulphuric acid.

Resistance To Staining And Burning

Test method to SS 42: 1971 or BS 3402: 1969 appendix D

No stain shall remaining either of the test pieces.

Warpage

Method to SS 42: 1971 appendix E

The warpage on the exposed surface of appliances shall not exceed 6mm (0.25 inch).

Dunt

Method to SS 42: 1971

Dunts shall not be allowed on any portion of an appliance.

Projections

Method to SS 42: 1971

Projects shall not be allowed on any portion of an appliance.

Minimum Thickness

Method to SS 42: 1971

The thickness at any place in an appliance shall not be less than 6mm (0.25 inch), and the thickness at the flushing surface shall not be less than 8mm (5/16 inch).

Tolerances

The permissible tolerances on dimensions specified as to SS 42: 1971 are:

  1. on dimensions not less than 75mm (3 inches), +/- 2%
  2. on dimensions less than 75mm (3 inches), +/- 5% and
  3. on the height of the flush outlet of P traps, +/- 4mm (5/32 inches)