BS-EN-13258-2003.pdf

BRITISH STANDARD BS EN 13258:2003 Materials and articles in contact with foodstuffs Test methods for crazing resistance of ceramic articles The European Standard EN 13258:2003 has the status of a British Standard ICS 67.250; 97.040.60 ? BS EN 13258:2003 This British Standard was published under the authority of the Standards Policy and Strategy Committee on 14 March 2003 © BSI 14 March 2003 ISBN 0 580 41408 6 National foreword This British Standard is the official English language version of EN 13258:2003. It supersedes DD ENV 13258:1999 which is withdrawn. The UK participation in its preparation was entrusted to Technical Committee CW/29, Tableware, which has the responsibility to: A list of organizations represented on this committee can be obtained on request to its secretary. Cross-references The British Standards which implement international or European publications referred to in this document may be found in the BSI Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Search” facility of the BSI Electronic Catalogue or of British Standards Online. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. aid enquirers to understand the text; present to the responsible international/European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; monitor related international and European developments and promulgate them in the UK. Summary of pages This document comprises a front cover, an inside front cover, the EN title page, pages 2 to 10, an inside back cover and a back cover. The BSI copyright date displayed in this document indicates when the document was last issued. Amendments issued since publication Amd. No. DateComments EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM EN 13258 March 2003 ICS 67.250; 97.040.60 English version Materials and articles in contact with foodstuffs - Test methods for crazing resistance of ceramic articles Matériaux et articles en contact avec les denrées alimentaires - Méthodes d'essai de la résistance au tressaillage des articles en céramique Werkstoffe und Gegenstände in Kontakt mit Lebensmitteln - Prüfverfahren für die Haarrissbeständigkeit keramischer Gegenstände This European Standard was approved by CEN on 21 November 2002. CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Management Centre or to any CEN member. This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the Management Centre has the same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, Slovak Republic, Spain, Sweden, Switzerland and United Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION COMITÉ EUROPÉEN DE NORMALISATION EUROPÄISCHES KOMITEE FÜR NORMUNG Management Centre: rue de Stassart, 36 B-1050 Brussels © 2003 CENAll rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 13258:2003 E EN 13258:2003 (E) 2 Contents page Foreword3 1Scope 4 2Terms and definitions4 3Principles4 4Apparatus .4 5Samples 5 6Procedure .5 7Expression of results 6 8Test report 7 Annex A (informative) Calculation of a Crazing Resistance Index from data obtained by method A.8 Annex B (informative) Calculation of a Crazing Resistance Index from data obtained by Method B.10 EN 13258:2003 (E) 3 Foreword This document (EN 13258:2003) has been prepared by Technical Committee CEN/TC 194 “Utensils in contact with food”, the secretariat of which is held by BSI. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by September 2003, and conflicting national standards shall be withdrawn at the latest by September 2003. This document supersedes ENV 13258:1998. Annexes A and B are informative. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, Slovak Republic, Spain, Sweden, Switzerland and the United Kingdom. EN 13258:2003 (E) 4 1 Scope This European Standard specifies two test methods (methods A and B) for the determination of crazing resistance of glazed ceramic tableware articles in contact with food with water absorption higher than 0,5 % (determined according to method C of EN 1217:1997). Method A is a test for resistance to crazing due to moisture expansion. Method B is a test for resistance to crazing due to thermal shock and is similar in most respects to EN 1183:1997. 2 Terms and definitions For the purposes of this European Standard, the following terms and definitions apply. 2.1 crazing formation of very fine cracks in the glaze caused by either moisture expansion of the body or thermal stress which creates sufficient tension in the glaze to cause it to craze 2.2 moisture expansion expansion of ceramic bodies with high water absorption due to penetration of water vapour through imperfections in the glaze 2.3 thermal shock sudden change in temperature 3 Principles 3.1 Method A The samples are subjected to saturated steam at a defined pressure for a number of cycles in an autoclave to test resistance to crazing due to moisture expansion. The steam pressure is increased and reduced slowly in order to minimize thermal shock. The samples are examined for crazing after each cycle. A stain is applied to the surface to aid in the detection of crazing cracks. 3.2 Method B Samples are heated in a test oven and then cooled rapidly in a cold water bath under controlled conditions in order to subject the articles to thermal shock. Thermal shock tests are repeated using increasing temperature differences. The samples are examined for crazing after each thermal shock test. The water in the cold water bath is stained to aid in the detection of crazing cracks. 4 Apparatus NOTEItems 4.1, 4.2 and 4.3 are required for method A and items 4.4, 4.5, 4.6, 4.7 and 4.8 are required for method B. 4.1Autoclave of sufficient volume to contain several samples, built for a steam pressure of at least 500 kPa. The steam may be provided by either external or internal heating of the autoclave or from a separate steam generator. The autoclave shall be equipped with: a pressure gauge; a safety valve; a means to reduce pressure within the autoclave to atmospheric pressure for safe opening at the end of each cycle and a means of controlling the steam pressure at (340 ± 34) kPa. 4.2Aqueous solution containing (5 ± 1) g/l of eosine and (5 ± 1) g/l of domestic washing up liquid. EN 13258:2003 (E) 5 4.3Soft cotton cloth 4.4Cold water bath, comprising a bath or tank capable of containing at least five times the apparent volume of the overall dimensions of the samples being tested at one time (including the basket), fitted with a water circulator, a thermometer and a thermostatic control capable of maintaining, for the duration of all the tests, the water temperature to within ± 2 °C of a specified lower temperature, t2, within the range 10 °C to 20 °C. 4.5Test oven, preferably electrically heated, having a temperature operating range of up to at least 300 °C, fitted with an air circulating device to ensure that the temperature variation does not exceed ± 5 °C and a thermostatic control capable of maintaining the temperature to within ± 2 °C up to 180 °C and to within ± 3 °C above 180 °C. 4.6Basket, for testing two or more samples simultaneously, made out of, or coated with, an inert material which will not damage the surface of the samples during the test procedure. The basket is capable of holding the samples in a position which ensures that air escapes and liquid can immediately enter the inside of holloware. The samples are held separately to allow free passage of water between them. The basket is fitted with clamps to prevent the samples from floating when immersed. NOTEFor the multiple testing of samples, the basket may be combined with an automatic device for inserting it in the test oven (4.5) and transferring it to the cold water bath (4.4). 4.7Tongs, with tips protected by a heat resisting material such as glass or mineral wool. 4.8Gloves, gauntlet-type, made from a heat resisting material. 5 Samples The complete test shall be performed on not less than 7 whole unused samples. NOTEDue to slightly different manufacturing methods it is advisable to test both holloware and flatware 6 Procedure 6.1 Method A 6.1.1Remove any dirt or loose debris from the samples; examine to verify that they are free from crazing. 6.1.2Place the samples on a suitable support in the autoclave (4.1) at least 5 cm above the water line at room temperature and in such a way that there is a clear space between them and then close the autoclave. 6.1.3Raise the pressure in the autoclave gradually for a period of not less than 15 min and not more than 1 h until it reaches 340 kPa and maintain at (340 ± 34) kPa for 2 h. 6.1.4Allow the pressure in the autoclave to fall to atmospheric. Allow the samples to cool for 1 h and then open the autoclave and remove the test samples. 6.1.5Immerse the samples in the staining agent (4.2) for (5 ± 1) min, then wipe off the stain with the cotton cloth (4.3). 6.1.6Inspect each sample immediately for crazing and determine the number of samples which have failed the test. 6.2 Method B 6.2.1Remove any dirt or loose debris from the samples; dry them if necessary and examine to verify that they are free from crazing. EN 13258:2003 (E) 6 6.2.2Fill the cold water bath (4.4) with water containing a staining agent, to a volume equal to not less than five times the apparent overall volume of the samples to be tested (including the volume of the basket) and to a depth sufficient for complete immersion of the samples plus not less than 50 mm. NOTEA suitable staining agent is eosine introduced at a concentration of (5 ± 1) g/1. Locate the water bath near to the test oven (4.5) and adjust and maintain the water temperature to within ± 2 °C of the specified lower temperature, t2. 6.2.3Place the samples, either separately or contained in the basket (4.6) in the test oven which has been previously heated to the upper temperature, t1. Maintain the samples at this temperature until they have reached equilibrium. NOTEThe time taken for samples to reach equilibrium with temperature t1 may be determined by simple experimentation with an equivalent mass of sand. The sand is placed in a beaker with a thermometer inserted into the centre of the body of sand and heated in the test oven. The time taken to reach temperature t1 is noted and a safety margin of 5 min is added. 6.2.4Remove the samples from the test oven either, one at a time, holding them with the tongs (4.7), or if the samples are large or contained in a basket with the gloves (4.8). Immerse the samples completely in the cold water bath without impact for a specified period between 8 s and 2 min ensuring that holloware is filled with water. Complete the process of transferring each sample, or the basket with samples, from opening of the test oven to immersion in (5 ± 1) s. Ensure that the difference in temperature between the test oven and the cold water bath is not more than ± 3 °C from the required temperature at the time of transference. 6.2.5Remove the samples from the cold water. Inspect each sample immediately for crazing and determine the number of samples, which have failed the test. 6.3 Determination of crazing resistance 6.3.1 Method A Repeat the testing procedure according to method A until all samples have failed. NOTEIt is envisaged that all samples will fail before the completion of the fifth cycle. Where this does not happen it is considered that the result will not change significantly with extended testing. Therefore, terminate the procedure after the seventh cycle. 6.3.2 Method B Commence testing with a temperature difference value t1 - t2 of (100 ± 5) °C and increase t1 by 20 °C increments. Repeat the testing procedures according to method B with increasing temperature difference values, t1 - t2, until all samples have failed. NOTEIt is envisaged that all samples will fail before a temperature difference value, t1 - t2 , of 200 °C is reached. Where this does not happen it is considered that the result will not change significantly with extended testing. Therefore, terminate the procedure after a temperature difference value, t1 - t2, of 200 °C is reached. 7 Expression of results 7.1 Crazing 7.1.1 Method A The cycle number at which each sample fails the crazing test is recorded together with the cumulative time T hours (cycle number × 2 for each sample). Any samples, which survive 7 cycles, are also reported. EN 13258:2003 (E) 7 7.1.2 Method B Samples which craze are recorded as having failed the crazing test at a temperature difference of t1 - t2. Any samples, which survive at the maximum temperature difference of 200 °C, are also reported. 7.2 Crazing resistance 7.2.1 Method A Record the number of failures after each 2 h cycle and the number that survive 7 cycles. Calculate a Crazing Resistance Index in accordance with the examples given in annex A. 7.2.2 Method B Record the number of failures at each temperature difference and the number of samples that survive at the maximum temperature difference of 200 °C. Calculate a Crazing Resistance Index in accordance with the examples given in annex B. 8 Test report The test report shall include the following details: a) a reference to this European Standard; b) an identification of the samples tested; c) the number of samples taken for the test and the sampling method; d) for the crazing test: the test method used, i.e. A or B; for each sample the cumulative time for method A or the temperature difference t1 - t2 in degrees Celsius for method B; the number of samples which failed the test at each cycle for method A or at each temperature increment for method B. e) for the Crazing Resistance Index test: the test method used for crazing, i.e. A or B; the Crazing Resistance