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International Crystal Federation  Technical Exchange Conference Waterford, Ireland  12 – 14 October 2002 Lead Migration from Crystal Glassware: Developments.

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Presentation on theme: "International Crystal Federation  Technical Exchange Conference Waterford, Ireland  12 – 14 October 2002 Lead Migration from Crystal Glassware: Developments."— Presentation transcript:

1 International Crystal Federation  Technical Exchange Conference Waterford, Ireland  12 – 14 October 2002 Lead Migration from Crystal Glassware: Developments from 12 Years of ICF TECs. Richard Lehman Professor of Materials Engineering Rutgers University New Brunswick, New Jersey USA

2 International Crystal Federation  Technical Exchange Conference Waterford, Ireland  12 – 14 October 2002 Outline of Presentation  Historical background  Structure/durability relationships  Effect of oxides  Migration behavior of lead crystal  Phenomenological behavior  Migration levels  Surface films – formation and properties Intrinsic Extrinsic  Other interesting effects

3 International Crystal Federation  Technical Exchange Conference Waterford, Ireland  12 – 14 October 2002 Historical Perspective  Work by Thorpe and Mellor, circa 1900  SiO 2 forms the network Covalently bonded Structural network of glass, promotes durability  Most other oxides modify the network Mostly ionically bonded Weak, promote migration and low durability  All other effects are secondary

4 International Crystal Federation  Technical Exchange Conference Waterford, Ireland  12 – 14 October 2002 Glass Networks and Modifiers

5 International Crystal Federation  Technical Exchange Conference Waterford, Ireland  12 – 14 October 2002 Glass Structure via Volume Filling Model

6 International Crystal Federation  Technical Exchange Conference Waterford, Ireland  12 – 14 October member Rings Dominate Glass Structure  Network bonding issues:  Each ring has 6 silicon participating in ring.  Each silicon is also part of three other rings  Each ring has 6/4 = 1.5 equivalent whole silicons  Migration and diffusion issues:  Nonbridging oxygens provide diffusion transfer site.  One nonbridging oxygen is required per ring to produce continuous diffusion path.  Mole ratio of 1.0/1.5 = 0.67 is upper limit for a diffusion-stable structure. Six-Member Silicate Ring Structure with One Non-bridging Oxygen Linkage nonbridging oxygen

7 International Crystal Federation  Technical Exchange Conference Waterford, Ireland  12 – 14 October 2002 Chain Structure of Certain Silicate Glasses Tetrahedral network structure of silicate glass

8 International Crystal Federation  Technical Exchange Conference Waterford, Ireland  12 – 14 October 2002 Expert Perspective “…we know practically nothing about…glasses” – W. H. Zachariasen, April “Glass is a difficult material” – Michael J. Hynes, April “I hope I die before I get old” – Pete Townshend, “My Generation”

9 International Crystal Federation  Technical Exchange Conference Waterford, Ireland  12 – 14 October 2002 Lead Release from Silicate Glasses with Varying Mole Ratio of Modifier and Formers.

10 International Crystal Federation  Technical Exchange Conference Waterford, Ireland  12 – 14 October 2002 General Effect of Oxides  Good Oxides  Al 2 O 3  TiO 2  ZrO 2  SiO 2  SnO 2  Important Parameters  Z/R [charge to radius]  Steric hindrance  Network connectivity  Bad Oxides  Li 2 O  Na 2 O K2OK2O B2O3B2O3  PbO  Medium Oxides  CaO  ZnO  MgO  BaO  PbO Radius  Z/R Steric Effects Chemical Durability  Overall Behavior

11 International Crystal Federation  Technical Exchange Conference Waterford, Ireland  12 – 14 October 2002 Participation of Intermediates in Silicate Glass Network Pb in 2/4 fold- coordination Al in 4 fold- coordination with Na + charge compensation

12 International Crystal Federation  Technical Exchange Conference Waterford, Ireland  12 – 14 October 2002 Crystal Glass Compositions

13 International Crystal Federation  Technical Exchange Conference Waterford, Ireland  12 – 14 October 2002 Effect of Thorpe Ratio

14 International Crystal Federation  Technical Exchange Conference Waterford, Ireland  12 – 14 October 2002 More Thorpe Ratio Data

15 International Crystal Federation  Technical Exchange Conference Waterford, Ireland  12 – 14 October 2002 The Problem: Water Molecules! Water molecules on glass surface

16 International Crystal Federation  Technical Exchange Conference Waterford, Ireland  12 – 14 October 2002 Stages of the Migration Process Pb migration time MoMo Three Stages: Intercept – time independent extraction, corresponding to dissolution of surface deposits. Parabolic – root time behavior. Fick’s law diffusion Linear – Surface film formation rate = dissolution rate.

17 International Crystal Federation  Technical Exchange Conference Waterford, Ireland  12 – 14 October 2002 Chemical Attack on Glass  Basic solutions attack glass network  Linear time dependence  Network and modifiers are dissolved together  Acid solutions leach modifiers from silicate network  Initial time independent dissolution of surface lead  Parabolic time dependence, Fick’s law diffusion, as silica gel forms.  Linear time dependence when diffusion rate is less than silica get dissolution rate. Original Glass Surface Silica Surface Film Bulk Glass Original Glass Surface Bulk Glass

18 International Crystal Federation  Technical Exchange Conference Waterford, Ireland  12 – 14 October 2002 December 1993 Pb Migration Status [Waterford, IR – John Kennedy]  Leaching kinetics  Parabolic Fickian behavior and intercept well recognized  Long-time linear and constant effects not documented  Methods to reduce migration  Glass composition Alkali reduction and mixed alkali effect [Na/K ~ 0.8 – 1.0 mole ratio] Lead-free glass and low-lead glass compositions [Ba, Sr, Bi] “Good” and “Bad” oxides

19 International Crystal Federation  Technical Exchange Conference Waterford, Ireland  12 – 14 October Pb Migration Status […continued]  Surface Treatments  Physical Rinse Cased gob [lead free lining] Polymer coating Sol-gel coatings Other coatings  Chemical Acid polish In-situ silica gel formation and condensation [preleach and cure] Ammonium sulfate fuming [modifier extraction from surface] Ion exchange [kaolin process – Al +3 exchange]

20 International Crystal Federation  Technical Exchange Conference Waterford, Ireland  12 – 14 October 2002 Parabolic Migration Behavior in Lead Crystal Glassware Pb,  g/l (time, h) h24 h Plain Acid Polished Pierre Ayral (Sep 92) 490 Typical 2002 ISO Value = 150 – 200  g/l

21 International Crystal Federation  Technical Exchange Conference Waterford, Ireland  12 – 14 October 2002 Low Incremental Migration on Cyclic Exposure  High initial levels due to surface lead  Formation of surface film provides diffusion limited process at longer times.  Levels can increase with aging or annealing after leaching unless surface film is heat cured. Pb,  g/l Cycles Plain Acid Polished Pierre Ayral (Sep 92) 200

22 International Crystal Federation  Technical Exchange Conference Waterford, Ireland  12 – 14 October 2002 Cyclical Behavior – many cycles Pb release, first exposure = 1.0 Cycles P. Stanghellini (Sep 92) 800 ~ Range

23 International Crystal Federation  Technical Exchange Conference Waterford, Ireland  12 – 14 October 2002 Lead Release into Whiskey from Decanters Whiskey A, B, C, D, E are various manufacturers

24 International Crystal Federation  Technical Exchange Conference Waterford, Ireland  12 – 14 October 2002 Four Years of Continuous Leaching Pb release, ug/l Weeks G. Boschi, F. Paloschi, P. Stanghellini, CALP (1996) 1000 Acetic Acid 500 Whiskey & Brandy Lead release increases with time ~40% of 4 year value is achieved after 8 weeks

25 International Crystal Federation  Technical Exchange Conference Waterford, Ireland  12 – 14 October 2002 Lead Crystal Stabilization with Alcohol  Lead concentration does not monotonically increase, but becomes constant after several months.  Reported by Himpens in 1995  Possible passivation of the glass with organic groups Blocking of silica gel interstices Greatly reduce solubility of silica gel, tetra ethyl orthosilicate is immiscible with aqueous solutions. Pb, arbitrary time, months 2 months Not Polished Acid Polished 4% Acetic Acid Whiskey, Bells 48 months Original Glass Surface Silica Surface Film Bulk Glass Si(OC 2 H 5 ) 4 layer, immiscible with water?

26 International Crystal Federation  Technical Exchange Conference Waterford, Ireland  12 – 14 October 2002 Calculated Extraction Depth [24% PbO Crystal] Original Glass Surface Silica Surface Film Bulk Glass 10 nm

27 International Crystal Federation  Technical Exchange Conference Waterford, Ireland  12 – 14 October 2002 Lead Near the Glass Surface E. Guadagnino, M. Verità ( ) Model derived from surface analysis results using XPS and EDS [EMPA] Elemental lead [Pb o ], possibly due to flaming, was found in one study, but not in a subsequent study]

28 International Crystal Federation  Technical Exchange Conference Waterford, Ireland  12 – 14 October 2002 Alternative Approaches to Limiting Pb Migration  Surface Treatments  Ammonium sulfate fume Remove surface alkali and lead Inexpensive and easy Better long term behavior than acid treatment x Requires high temperature x Deformation of stemware  Sol-gel  Ion exchange – Al +3 from kaolin -- ~  g/l [6-60 months in HAc]  Preleach  Preleach with silica gel condensation – 448  g/l  50, 300 autodish cycles  Polymer coating – 60  g/l from wine Waterford (1991) Lenox (1992) Rutgers (1995)

29 International Crystal Federation  Technical Exchange Conference Waterford, Ireland  12 – 14 October 2002 Alternative Approaches to Limiting Pb Migration  Batch formula changes  Reduced alkali – but need to substitute to retain working properties  1% phosphate addition – effect shown in very high lead glass only  Reduced PbO [w/o Polish: 24% (240  g/l ); 18% (30  g/l ); 12% (50  g/l )]  Others  Leadless glass liner – cased gob -- <20  g/l  Leadless crystal – SiO 2 [56.1%], (Na,K) 2 O [10.4], BaO [26.1], Ca,Zn [2.4]

30 International Crystal Federation  Technical Exchange Conference Waterford, Ireland  12 – 14 October 2002 Non-Lead Crystal  Aimed initially to replace category 3 glass [5% PbO]  Has evolved for all types  Category 1: 30% PbO, >1.545, >3.0 g/cm 3  Category 2: 24% PbO, >2.9 g/cm 3  Category 3: 5% PbO, >1.52, >2.45 g/cm 3 Bo Jonson (1996)

31 International Crystal Federation  Technical Exchange Conference Waterford, Ireland  12 – 14 October 2002 Effect of PbO Level in Glass and Repeated Extractions First exposure Second & third exposure E. Guadagnino (1997)

32 International Crystal Federation  Technical Exchange Conference Waterford, Ireland  12 – 14 October 2002 Atlantis Batching Changes [1986 – 1994]  Minor changes:  SiO 2 slightly up  PbO slightly down  Zinc removed, barium added, MgO tested  And:  B 2 O 3 returning towards 1986 levels  Antimony replaces Arsenic [Cardeira, 1995]

33 International Crystal Federation  Technical Exchange Conference Waterford, Ireland  12 – 14 October Leach Data -- Atlantis

34 International Crystal Federation  Technical Exchange Conference Waterford, Ireland  12 – 14 October 2002 Surface Treatments: Acid Pretreatment & Cure  Acid rinse to remove surface modifiers  Cure to condense silicic acid surface film.  0.05 ug/cm 2 = 25 ug/l for 1 liter round cylinder with h/r = 3. Durable film, withstands 300 autodish cycles

35 International Crystal Federation  Technical Exchange Conference Waterford, Ireland  12 – 14 October 2002 Mathematical relationships for surface film formation  Incorporate measured activation energy for lead migration with Fick’s law.  Use to predict migration results.

36 International Crystal Federation  Technical Exchange Conference Waterford, Ireland  12 – 14 October 2002 Polishing and (NH 4 ) 2 SO 4 Examples Hande Sengel, Sisecam (1997)  Polishing gives ~75% reduction in lead release.  Sulfate treatment gives an additional ~33% reduction.

37 International Crystal Federation  Technical Exchange Conference Waterford, Ireland  12 – 14 October 2002 Aging Increases Lead Release Non-polished glass Bo Jonson (1997) Also: Glass forming deposits Pb, Na, K modifier on surface Aging brings same modifiers to surface. E. Guadagnino (2000)

38 International Crystal Federation  Technical Exchange Conference Waterford, Ireland  12 – 14 October 2002 Summary  Lead glasses follow generally well-identified acid leaching behaviors

39 International Crystal Federation  Technical Exchange Conference Waterford, Ireland  12 – 14 October 2002 Summary  Lead glasses follow generally well-identified acid leaching behaviors  Large body of early work collected data for specific compositions and leachates  Varied crystal compositions  Varied solutions, esp. alcohol  Patterns of use identified to match migration with ingestion

40 International Crystal Federation  Technical Exchange Conference Waterford, Ireland  12 – 14 October 2002 Summary  Lead glasses follow generally well-identified acid leaching behaviors  Large body of early work collected data for specific compositions and leachates  Varied crystal compositions  Varied solutions, esp. alcohol  Patterns of use identified to match migration with ingestion  Focus on composition changes, good and bad oxides

41 International Crystal Federation  Technical Exchange Conference Waterford, Ireland  12 – 14 October 2002 Summary  Lead glasses follow generally well-identified acid leaching behaviors  Large body of early work collected data for specific compositions and leachates  Varied crystal compositions  Varied solutions, esp. alcohol  Patterns of use identified to match migration with ingestion  Focus on composition changes, good and bad oxides  Surface modification technologies and characterization have had dominant role over past ~5 - 7 years  Claddings, Coatings, Treatments, Advanced surface analysis  Some inexpensive, others not, all require an additional step  BUT, decouples migration behavior from most other glass requirements  End-use specific assessments, e.g. dishwasher performance

42 International Crystal Federation  Technical Exchange Conference Waterford, Ireland  12 – 14 October 2002 Summary  Lead glasses follow generally well-identified acid leaching behaviors  Large body of early work collected data for specific compositions and leachates  Varied crystal compositions  Varied solutions, esp. alcohol  Patterns of use identified to match migration with ingestion  Focus on composition changes, good and bad oxides  Surface modification technologies and characterization have had dominant role over past ~5 - 7 years  Claddings, Coatings, Treatments  Some inexpensive, others not, all require an additional step  BUT, decouples migration behavior from most other glass requirements  End-use specific assessments, e.g. dishwasher performance  General observations  Migration levels are well below ISO limits  Durability, in combination with other required properties and economic considerations, may be nearly optimized within traditional lead crystal glassware definitions.  Environmental issues will continue to be important  Lead workplace issues will continue to impact lead use in glassware.

43 International Crystal Federation  Technical Exchange Conference Waterford, Ireland  12 – 14 October 2002 Future Opportunities  Glass Composition  Combinatorial assessment of non-linear composition space  Role of minor constituents to improve durability  Surface Treatments  Surface film formation/modification below optical limits  Chemical complexing agents to bond surface.

44 International Crystal Federation  Technical Exchange Conference Waterford, Ireland  12 – 14 October 2002 Partial List of Acknowledgements  Atlantis: Carlos Fonseca  CALP: Paulo Barducci, Pietro Stanghellini, Fabio Paloschi  FFC: Pierre Ayral  Glafo: Bo Jonson, Stellan Persson  Inst. Chem. Tech.: Miroslav Rada  Lalique: Paul Cordie  Lenox: John Potts  Nachtmann: Walter Frank  Orrefors, Glasma: Arne Fransson  Sisecam: Hande Sengel  St. Georges Crystal: Robert Gonze, Jerry Kynik  Staz. Sperimentale del Vetro: Emanuel Guadagnino  Tyrone: Colin McGookin  Verrerie Cristallerie D’Arques/JG Durand: Etienne Himpens  Waterford: John Kennedy


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