DRAFT TANZANIA STANDARD  
 
 
 GDC 4 (1) DTZS  Tableware -Ceramic Ware -Specification  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
TANZANIA BUREAU OF STANDARDS  
 
 
 
©TBS 2021                                                                                                       1st    Edition
 
1 
 1. Scope  
 
This d raft Tanzania standard specifies requirements, method of sampling and te st for ceramic  ware . 
2. Normative references  
The following documents are referred to in the text in such a way that some or all of their content constitutes 
requirements of this document. For dated references, only the edition cited applies. For undated references, 
the latest edition of the referenced do cument (including any amendments) applies.  
ISO 6486 -1:2019  Ceramic ware, glass ceramic ware and glass dinnerware in contact with food — Release 
of lead an d cadmium — Part 1: Test method.  
ISO 6486 -2:1999 Ceramic ware, glass -ceramic ware and glass dinnerware  in contact with food — Release 
of lead and cadmium — Part 2: Permissible limits . 
IS 14179:1999 Methods of test for ceramic tableware . 
3. Terms and definitions  
For the purpose of this document, the following terms and definitions shall apply ; 
  
3.1 c eramic ware  
ceramic articles which are intended to be used in contact with foodstuffs, e.g. food ware made of burnt 
clay, porcelain and earthenware, whether glazed or not  
 
3.2 crazing (or Craze )  
hair like cracking which occurs in fired glazes or other ceramic coatings  due to critical tensile stresses  
 
3.3 ceramic decoration colour  
preparation consisting of coloured or colourless glass powd er and inorganic pigments  for coating of 
ceramics or glass by melting at temperatures above 450 °C  
 
3.4 chipping resistance   
ability of ceramic ware to resist the removal of any portion of its  surface as a result of impacts  
 
3.5 flatware  
Ceramic  ware  which has an internal depth not exceeding 25 mm, measured from the lowest point to the 
horizontal plane passing through the point of overflow  
 
3.6 glaze  
ceramic coating matured to glassy state on a formed ceramic article, or the material or mixture from which 
the coating is made   
 
3.7 hollowware  
ceramic ware having an internal depth greater than 25  mm, measured from the lowest point to the horizontal 
plane passing through the point of overflow. Hollowware is subdivided into three categories based on 
volume:  
— small: hollowware with a capacity  < 1,1 L; 
— large: hollowware with a capacity of  ≥ 1,1 L; 
— storage: hol lowware with a capacity of  ≥ 3 L; 
— cups and mugs: small ceramic hollowware commonly use d for consumption of beverages,  e.g., 
coffee or tea at elevated temperature.  
  
2 
 Note 1 to entry: Cups and mugs are vessels of approximately 240  ml capacity with a handle. Cups typically 
have curved sides whereas mugs have cylindrical sides.  
 
3.8 thermal Shock  
condition of stress brought about by a large temperature di fference across a body or glaze  
 
3.9 vitreous (Vitrified)  
degree of vitrification evidenced by low water absorption  
 
NOTE — The term 'vitreous' generally signifies less than 0.5 percent water absorption.  
 
3.10 w arpage  
deviation from flatness  
 
4. Requirements  
4.1 General Requirements  
 
4.1.1  The ceramic ware shall be totally glazed except in areas which are for support during  firing, but such 
unglazed surfaces shall be smooth and polished. The glaze shall be even, free  from cracks, and shall 
possess an impervious surface. It shall be free as possible from  pinholes, blisters, iron spots, glaze jumps, 
glaze runs, waxy glaze and pitting . 
 
4.1.2 The ceramic ware shall possess a good or high -pitched metallic ring whenever tapped  with anything 
hard, of good workmanship, and free as possible from manufacturing defects  like welts, chips, craze, 
specks, crawling or other imperfections detracting from the sight.  
 
4.1.3 The ceramic ware  with a lip and spout, it shall be of suitable  design so that the liquid does not drip 
outside while pouring.  
 
4.1.4 The handle when provided shall always be symmetrical  and must able to support the weight of ceramic 
ware and its content.  
 
4.1.5 The materials used for the body and glaze shall be of a true porcelain mix. These are  feldspar, silica 
and kaolin.  
 
4.1.6 Types  of decoration can either be over glaze, in -glaze, or underglaze  and can be made of gold, 
platinum, or ceramic pigments and stains . 
 
4.2 Specific Requirements  
 
4.2.1  Ceramic d ecoration  colour  
 
4.2.1.1 The Ceramic decoration colo ur shall be highly resistant to acid with a maximum  toleranc e up to 
Grade No. 1 (see Table 1 ) when tested in accordance with  the method given  in Annex  H. 
4.2.1.2 The Ceramic decoration colour  on the surface of the ware shall be highly resistant to  alkali to Grade 
No. 2 (see Table 1 ) when tested in accordance with the method given  in Annex  H. 
4.2.1.3 The Ceramic decoration colour  on the ware surface shall be highly resistant to  boiling water with a 
maximum toleran ce up to Grade No. 1  (see Table 1 ) when tested in accordance with  the method given in  
Annex  H.  
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 4.2.1.4  The Ceramic decoration colour  on the ware surface shall be highly resistant to household detergent 
with a maximum tolerance up to Grade No. 1 (see Table 1 ) when tested in accordance the method given  
in Annex G.  
 
Table 1 - Grades based on chemical test result  
Item Grades  
0 1 2 3 
Surface luster  Unchanged  Slightly ma tte Considerably  matte  No luster  
Color fading  Unchanged  Slightly  fading  Considerably  fading  Extreme  fading  
 
4.2.2  Limits release of Lead and Cadmium  
 
The permissible limits for Le ad and cadmium for ceramic ware , when tested in accordance with ISO 6486 -
1:2019 , shall conform to the requirements given in Table 2 . 
 
Table 2 -Permissible limits for Lead and cadmium release  
 
Type of ware  Permissible limits  (mg/ l) 
Lead Limit  
(Max imum )   Cadmium limit  
 (Max imum)  
Small 
hollowware  2 0.5 
Large 
hollowware  1 0.25 
Storage 
hollowware  0.5 0.25 
Cups and 
Mugs  0.5 0.25 
Cooking ware  0.5 0.05 
Flatware  Permissible limits (mg/dm2) 
0.8 0.07 
 
4.2.2 The ceramic ware shall conform to the requirements  indicated in table 3 .  
Table 3 -Requirements for C eramic ware  
Parameter  Requirement  Test 
method  
Thermal shock  , °C Minimum  160 Annex A  
Chipping resistance , Nm Minimum  0.14 Annex B  
Impact strength  ,Nm Minimum  0.267  Annex C  
Water absorption % ,Maximum  0.4 Annex D 
Crazing  None of the test pieces show crazing  
 Annex E 
 
4.2.3  Warpage  
 
4.2.3.1  Out-of-Roundness  
The out -of-Roundness of various items tableware  shall not exceed 1% on the nominal diameter when 
measured in accordance with the method prescribed in F.1 of Annex F.  
4.2.3.2  Edge - Warpage and Slope of Flatware   
4 
 The edge -warpage and sl ope of the flatware shall not exceed 2 mm and 2 ° respectively when  measured in 
accordance with the method prescribed in F .2 of Annex F . 
4.2.3.3  Flatness of Dinner Plate  
The eating surface of the  plate shall be flat  within 2 mm total indicator run out when measured in accordance 
with the method prescribed in in F .3 of Annex F.  
 
4.2.4  Resistance to Detergents  
 
When tested - by the method prescribed in Annex I, the test article shall not show any loss of  gloss of the 
glaze when compared with the untested  test specimen . 
 
5. Packing and marking  
 
 5.1 Packing  
The ceramic ware  shall be packed as agreed between the supplier and the purchaser.  
5.2 Marking  
Each article of the ceramic ware  shall be indelibly and legib ly marked with the following information ; 
a) Manufacturer’s name and /or recognized trade mark . 
b) country of origin .  
c) The words ‘FOR FOOD CONTACT’, or the Food safety symbol as shown  in Annex J. 
 
6 . Sampling  
 
6.1 Lot 
All the cera mic ware items of the same shape, size and material and belonging to the same batch of 
manufacture shall constitute a lot.  
6.1.1 Each lot shall be tested separately for all the requirements of the specification. The number of pieces 
to be selected from each lot for this purpose shall be as given in Table 3. 
6.1.2  The pieces shall be selected at random from each lot.  
6.2 Number of Tests  
6.2.1 Tests for all the requirements of workmanship, finish and visual assessment shall be done on  samples 
selected as per col 2 of Table 3 and tests for the remaining characteristics shall be performed on the 
samples selected as per col 4 of Table 3. 
6.3 Criteria for Conformity  
6.3.1 An item not complying with one or more than one requirements shall be termed as defective.  
6.3.2 For the lot to be accepted as conforming to the  requirements of workmanship, finish and visual  
assessment, the total number of defectives shall not  exceed the corresponding acceptance number as  
given in col 3 of Table 3.  
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 6.3.3 The lot having been found satisfactory according  to 6.4.2, shall be further tested for warpage, water  
absorption, resistance to detergents and resistance  to boiling citric acid on the samples selected as per  col 
4 of Table I. Resistance to abrasion shall be tested  on specially prepared unglazed  tiles (see Annex H.2). 
All the tests shall pass for the lot to be found satisfactory  according to these requirements.  
6.3.4 The lot having been found satisfactory according  to 6.4.3 shall then be tested for crazing resistance, 
impact  strength and chipping resistance, and resistance  to thermal shock.  
6.3.4.1 The samples shall conform to all the tests for  the lot to be accepted as conforming to the 
requirements  of the specification.  
 
Table 3  Scale of Sampling  
(clause 6.1.1,6. 2.1,6.3.2 and 6. 3.3) 
Lot Size  Permissible Number of Defectives  Sample Size  
Up to 150  0 2 
151 to 280  1 2 
281 to 500  2 3 
501 to 1200  3 3 
1201 to 3200  5 4 
3201 to 10000  7 5 
10001 to above  10 5 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
  
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 Annex A  
(clause 4.2.2)  
TEST FOR RESISTANCE TO THERMAL SHOCK  
A.1 Principle  
Thermal shock is measured by the difference between the upper temperature t1 to which the specimens 
are heated and the lower temperature t2 of the cold water -bath into which they are placed after heating. 
This is a test for tend ency of crazing due to residual stresses after firing and not due to factors of moisture 
expansion.  
A.2 Apparatus  
A.2.1 Air -Oven  
With a temperature range of 35 to 250°C and provided with an air stirrer or circulator to ensure uniformity 
of temperature. The  oven shall have a thermostat capable of maintaining the tempera ture constant to ± 1 
°C up to 180 °C and ±2°C between 180 and 250°C. It shall also be provided with a thermometer capable of 
being read to an accuracy of ±1°C. 
A.3 Reagent  
A.3.1 Eosin Solution  
0.5 percent (m/v) in water.  
A.4 Procedure  
A.4.1 Place three specimens in the air -oven previously heated to the upper temperature t1 so that the 
difference (t1 - t2) is equal to 120°C, t2 being the temperature of tap water in the cold water -bath. Maintain 
the samples in the oven at that temperature for 30 min. Then -remove the specimens from the oven, one 
at a time, by means of tongs with asbestos covered tips, completing the process of tra nsference in 5 ± 1 -5 
for each article, and immerse the specimens for a specified period of not less than two minutes into the cold 
water -bath which has been maintained at temperature t2. After immersing in the cold water -bath, dry the 
specimens and then im merse in the eosin solution. Examine the test specimens after cleaning. The -
specimens shall be subjected to this test five times.  
A.4.2 The specimens shall be considered to have satisfied the requirement of the test if there is no crazing 
of the glaze or c racking of the -ware indicated by coloured hair lines on the surface of any specimen . 
 
 
 
 
 
 
 
Annex B   
7 
 (clause 4.2.2)  
TEST FOR  CHIPPING  RESISTANCE  
B.1 Principle  
This test is carr ied out to ensure that the ceramic ware withstands impacts encountered in normal  day to 
day use without breaking or chipping.  
B.2 Apparatus  
B.2.1 Impact Tester  
A suitable pendulum type impact tester  
B.3 Procedure  
B.3.1 This test shall be carried out on flat ware only. Place the plate or saucer on ·its foot between two cast 
iron block s forming a 90° 'V' and adjust it in such a manner that when the hammer.is hanging vertically the 
center of the impact face of the chipping hammer touches the edge of the test piece at the plane of the 
bisector of the angle of the 'V'. Strike the test piec e at three equally spaced points on its periphery with the 
cylindrical end of the hammer with an impact force of 0.14 N.m . 
B.3.2  The ware shall be considered as not conforming the test if the impact results in chipping of the edge 
so that fragments of glaz e and body are removed.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Annex C   
8 
 (clause 4.2.2)  
TEST FOR  IMPACT STRENGTH   
C.1 Principle  
This test is carried out  to ensure that the ceramic ware withstands impacts encountered in normal day to 
day use without breaking or chipping.  
C.2 Apparatus  
C.2.1 Impact Tester  
A suitable pendulum type impact tester .  
C.3 Procedure  
When testing a plate, saucer or platter, support the  ware against th ree equally spac ed 3 mm diameter  steel 
halls so that when the hammer is hanging  vertically the impact point of hammer touches the  centre of the 
bottom of the test piece. When testing  a cup or bowl, place the ware on its foot between two  cast iron blocks 
forming a 90° 'V' whose sides are  sufficiently high to support the upper edge of the cup  or bowl and adjust 
it in such a manner that when the  hammer is hanging vertically, its impact point  touches the cup or bowl at 
its upper edge and on the  plane of the bisector of the angle of 'V ’. Strike the  test piece with the spherical 
end of the hammer with  an impact f orce impact of 0.267  N.m. 
9.3.1.1 A ware such as a plate, saucer or platter shall  be considered as not complying the test if it develops  
a rupture which appears as a hole through the body  or as a body crack extending through its rim. A cup  or 
bowl shall be  also treated as not conforming if it  develops a body crack extending into any portion of  the 
foot or a portion of the body breaks away.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Annex D   
9 
 (clause 4.2.2)  
TEST FOR  WATER ABSORPTION  
D.1 Principle  
Water absorption of the sample is determined by the  amount of water absorbed by boiling the sample In  
distilled water and finding the increase in the mass.  
D.2 Test Pieces  
Five test pieces from five different test samples are  cut or broken to get a surface area of about 16 cm2.At 
least two  flat faces of the test pieces shall be glazed  and other sides unglazed. The test samples shall be  
freshly cut or broken.  
D.3 Procedure  
Test pieces shall be dried at a temperature –between  110° and 120°C and then cooled to a room 
temperature  in a desiccato r. The test pieces shall be weighed  accurately to the nearest 0.01 g and then put 
in vessel  and evacuate the air maintaining the pressure at  less than three centimeters of mercury for 1 
introduce freshly boiled and cooled distilled water  into the vessel maintaining the vacuum until the  pieces 
are covered with water. Then admit air into  the vessel normalizing the pressure and boil the  pieces in 
distilled water for not less than 20 min.  Cool, wipe the pieces with a damp soft cotton cloth  to remove 
adhering surface water and weigh quickly . 
Water absorption of the test pieces shall be calculated  as follows:  
 
Water absorption, percent by mass =   (𝑀2−𝑀1)/𝑀1  ×100 
 
where  
M2 = mass in g of the soaked test piece after  boiling , and  
M1 = mass in g of the dry test piece.  
 
 
 
 
 
 
 
 
 
 
Annex E  
10 
 (clause 4.2.2)  
TEST FOR CRAZING RESISTANCE  
E.1 Procedure  
E.1.1 Fresh whole dry articles shall be subjected to the  crazing test. They shall be placed loosely at room  
temperature on a suitable support at least 50 mm above  water level in an autoclave which shall be of 
sufficient  capacity and equipped with a safety valve, blow -off valve; thermometer, pressure gauge and 
heating  arrangement or other means of sufficient capa city to  ensure constant steam pressure within the 
autoclave. Sufficient  amount of distilled water shall be taken in  the autoclave. Slight water will remain after 
the test.  Initially the blow -off valve shall be kept open until  steam begins to escape thereby  expelling most  
of the air. Also closing the blow -off valve, water shall be  kept boiling and the steam pressure increased at 
a uniform ra te until it reaches the pressure 5 kg/cm2 within  a period of 30 min or one and a half hour 
depending  on the kind of the ware and hold it at the maximum  pressure for 1 h. Sufficient heat shall be 
applied to  maintain a constant steam pressure for the specified  period.  
E.1.2 The source of heat shall then be shut off and steam  pressure released slowly in not less than 30 min  
by opening the blow off valve. The ware shall be  allowed to cool to room temperature in the autoclave. The  
wares then shall be removed and tested for crazing  by applying 0.5 percent eosin solution (m/v) in water  or 
blue black fountain pen ink to the glazed surface.  There should not be any hair like pattern after  application 
of the dye or ink.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Annex F   
11 
 (clause 4.2.2)  
TEST FOR WARPAGE  
F.1 Out -of-Roundness  
The out -of-roundness of the ceramic ware shall be  determined by use of a dial indicator. The sample, 
resting  on its foot on a flat surface, shall be blocked  in a manner to allow its rotation. The indicator  plunger 
shall strike the outer rim edge of the sample  from above at a 45° angle to a horizontal plan e. The  sample 
shall be rotated and the low and high readings  taken. The difference between the two readings shall  denote 
the out -of-roundness.  
F.2 Edge Warpage and Slope for Flatware  
Edge warpage and slope of items shall be determined  as follows:  
a) Invert the sample and place it face down on a surface plate.  
 
b) Place a weight across the resting surface of the item to stabilize it in place.  
 
c) Attempt to insert a feeler gauge between the surface and any portion of the sample edge. The 
reading of the feeler gauge  will indicate the warpage on the edge of the item.  
 
d) Remove the weight from the resting surface and replace it with an inclinometer.  
 
e) Determine the slope of the resting surface . 
 
F.3 Flatness  
The surface flatness of the eating area of the flatware  shall be  determined by using a dial indicator. The  
sample shall be adequately blocked and the  indicator stabilized to prevent a distorted reading. The  total 
runout  (flatness)  expressed in decimal value  shall be the summation of the 'high (convex ) and the low 
(conc ave) point encountered . 
 
 
 
 
 
 
 
 
 
 
 
Annex G   
12 
 (clause 4.2.2)  
TEST FOR RESISTANCE TO DETERGENTS  
G.1 Principle  
The ceramic ware articles are immersed into detergent  solution at a temperature of 60°C for 48 h and loss  
of gloss of the glaze is compared visually against  untested sample.  
G.2 Reagent  
G.2.1 Detergent  
 0.04 percent (m/v)  
G.3 Procedure  
Place fresh, clean whole article or piece in a suitable  beaker. Add detergent solution so that the article is 
completely immersed and then cover with watch glass. Place the beaker in an air oven for 48 h at a 
temperature  of 60°C. During the period of test, the concentration  of the detergent solution shall  be 
maintained  by adding required amount of water periodically. At  the end of the period, 'remove the test 
specimen, wa sh with water and dry. Compare the loss of gloss of glaze  of the test specimen visually against 
untested sample . 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Annex H   
13 
 (clause 4.2.1.1, 4.2.1.2,4.2.1.3 ) 
TEST METHOD FOR CERAMIC WARE DECORATION  
 
H.1 Boiling water proof test  
H.1.1 Principle  
This test determines if fired pigment or luster is affected  by boiling water.  
H.1.2 Procedure   
Leave the test piece at 100ºC controlled water bath for 24 hours. Wash, dry and observe for  changes in 
luster, color and peeling -off of pigments or gold. 
H.2 Alkali proof test  
H.2.1 Principle  
This test determines if fired pigment or luster is affected by alkali.  
H.2.2 Procedure  
Dip the test piece into a 0.5% solution of sodium carbonate in a controlled water bath at  100ºC for two 
hours. Wash, dry and  observe for change in luster, color and peeling -off of  pigments gold.  
H.3 Acid proof test  
 H.3.1 Principle  
This test evaluates the quality of design or decoration (gold or  platinum) on the ware surface and if fired 
pigments of gold on the ware is affected by acid.  
H.3.2 Procedure   
Dip the test piece into a four percent solution of acetic acid. Soak at 25 -55ºC for 24 hours. Wash thoroughly 
with water, dry with cloth and observe for any change in luster, color and  peeling -off of fired pigments or 
gold. 
 
 
 
 
 
 
 
 
 
 
Annex I   
14 
 (clause 4.2.4 ) 
TEST FOR RESISTANCE TO DETERGENTS  
I.1 Principle  
The tableware articles are immersed into detergent solution at a temperature of 60°C for 48 h and loss of 
gloss of the glaze is compared visually against untested sample.  
I.2 Reagent  
I.2.1 Detergent  
0.04 percent (m/v)  
I.3 Procedure  
Place fresh, clean whole article or piece in a suitable beaker. Add detergent solution so that the article is 
completely immersed and then cover with watch glass. Place the beaker in an air oven for 48 h at a 
temperature of 60°C. During the period of test,  the concentration of the detergent solution shall  be 
maintained by adding required amount of water periodically. At the end of the period, remove the test 
specimen, wash with water and dry. Compare the loss of gloss of glaze of the test specimen visually against 
untested sample.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Annex J   
15 
 (Informative ) 
FOOD SAFETY SYMBOL  
 
The international symbol for "food safe" material is a  wine glass  and a  fork symbol . The symbol indicates 
that the material used in the product is considered safe for food  contact. This includes food and water 
containers, packaging materials, cutlery etc . These can be made from a variety of materials including 
plastics, rubber, paper and metal. They also include materials used in processing equipment, such as coffee 
makers or production machinery as well as containers used for transport . 
   
 
Figure 1: International Food safety symbol