1. Reengineering Beauty: The Pros and Cons of Current Crystal Glass Manufacturing Methods Designed to Reduce Lead Migration
Presenters: Joseph Pantina
Joshua Finch
Timothy Tirrell
Advisors: Dr. Lehman
Dr. Crawford

2. Outline of Presentation
Overview of legislation restricting lead exposure and use
Summary of the role of lead in crystal
Structure
Migration
Review of selected processes to reduce lead migration
Surface Modification
Surface Coatings
Discuss advantages/disadvantages

3. Legislation regarding Lead
Proposition 65:
California’s Office of Environmental Health Hazard Assessment (OEHHA)
Lead leaching must not exceed:
- 226 ppb (for flatware)
-100 ppb (all other tableware)
Leaching test use 4% acetic acid solution at 22oC
Products failing to fall below “safe harbor levels” of lead must bear a warning.
REACH:
Registration, Evaluation, and Authorization of Chemicals
European Union initiative
Toxic chemicals must be registered upon their production
Chemicals must be tracked during all stages of its use in production
“Warning: This product contains chemicals known to the State of California to cause cancer and birth defects or other reproductive harm.”

4. Reasons for Lead in Crystal
Optical Properties:
- Increases index of refraction
- Increases dispersion of light
Mechanical Properties:
- Increases density
- Decreases hardness
Processing Properties:
- Improves glass workability
- Increases machinability

5. Chemical aspects of Lead in Crystal
Lead’s role as a glass former:
Some fraction of lead atoms occupy glass network positions
Covalently bonded to silicon in the silicate structure
Lead leaching of lead as a glass former:
Negligible for acidic solutions below ph=7
- Due to covalent bonds of lead glass formers
Low for alkaline solutions below pH=10
- Slow deterioration of silicate network; releases lead ions
High for alkaline solutions above pH=10
- Rapid deterioration of silicate network; releases lead ions
Lehman 2002

6. Chemical aspects of Lead in Crystal (Cont.)
Lead’s role as a glass modifier:
Large concentrations “open up” the lead silicate structure
Modifier lead ions are ionic bonded
Effect of acidic solutions:
H+/H3O+ ions compete with Pb2+ ions, via Coulombic forces
Pb2+ ion replacement forms a silanol layer (non-bridging oxygen)
≡Si-O-Pb-O-Si≡(s) + 2H3O+(sol) ≡SiOH(s) + Pb2+(sol) + 2H2O(sol)
*Note: 2(≡SiOH) allow for further ion diffusion through the non-bridged structure

7. Methods to reduce lead leaching must:
1)Maintain the quality and integrity of the original crystal
2)Reduction of lead leach rate below legislative standards
3)Maintain appearance and lowered leach rate after persistent use, including up to 500 dishwasher cycles

8. Methods for Reducing Lead Leaching
Surface Modification: changes the chemical composition of the crystal surface to provide a lead diffusion barrier.
Methods:
1) Pre-leaching/acid wash with subsequent annealing
2) Ammonium sulfate Fuming
3) Baccarat Ion Exchange Treatment
4) British Glass Microwave Assisted Ion Exchange
Surface Coating: coatings used to provide a lead-free barrier to lead diffusion from a crystal surface
1) Sol-Gel Coating
2) Chemical Vapor Deposition (CVD)
3) Schott Plasma Impulse Chemical Vapor Deposition (PICVD)

9. Pre-leaching/acid wash with subsequent annealing
Overview:
1) Crystal surface exposed to acidic solution to leach out lead ions
2) Surface layer of silanol is dehydrated by annealing
2(≡SiOH)(s) ≡Si-O-Si≡(s) + H2O(v)
3) Lead deficient silica surface layer is formed
Optimized Method: Reduced leach rates 24% Lead Crystal (Lehman 1997)
4% acetic acid solution at 40oC
9 minute pre-leach time
2 hour annealing at oC
Heat

10. Pre-leaching/acid wash with subsequent annealing (Cont.)
Lead leach rates of treated crystal under standard testing with 4% acetic acid solution at 22oC
Lead release in (µg/cm²) as a function of preleach time and annealing temperature
Pretreatment Temperature
Annealing Temperature
0 minutes
1 minute
9 minute
25 minute
(ºC)
average
100
0.38
0.21
0.15
0.16
 40
200
0.17
0.09
0.00
0.07
300
0.06
No detectable lead levels after lead leach test for samples pretreated for 9 minutes and annealed at 200oC
Comparison to lower pre-leach times show that 9 minutes can create a lead deficient silicate layer
Annealing temperature trends suggest that a heat treatment of at least 200oC is needed to densify the lead deficient layer to block further lead leaching

11. Ammonium Sulfate Fuming
Overview:
Ammonium sulfate is added to pre-annealed crystal
At annealing temperature, ammonium sulfate reacts with lead and potassium cations.
(NH4)2SO4 + Pb2+ + K PbSO4 + K2SO4 + NH3+ H2
Potassium and lead sulfate are precipitated on the crystal surface
Precipitates can be washed away to leave a lead depleted crystal surface layer

12. Ammonium Sulfate Fuming (Cont.)
British Glass investigated the addition of 0.1 g ammonium sulfate to crystal before annealing
Crystal annealed at 490oC
Precipitates were analyzed by chemical analysis, confirming the composition as potassium and lead sulfate
Standard Testing in a 4% acetic acid at 22oC
X-ray photoelectron spectroscopy (XPS) of the treated surface shows a 1/3 of Pb and 1/6 of K ions still remain compared to the untreated surface
Untreated
Treated
600 ppb Pb
40 ppb Pb

13. Baccarat Ion-exchange Treatment
Details obtained from:
“Process for treating lead glass to form a lead diffusion barrier in the surface thereof.” (US Patent # )
Overview:
An ion exchange slip is selected to provide non-toxic metal glass forming ions for exchange with lead ions.
Crystal surface is coated with ion exchange slip
Bulk crystal is heat treated to increase the diffusion rate of ions (Fick’s Law)
Non-toxic ions replace lead to form a diffusion barrier to further lead migration in the surface layer
Removal of “cemented” slip on the crystal surface

14. Baccarat Ion-exchange Treatment (Cont.)
Type of slip utilized:
Kaolin or hydrated aluminum silicate
- Both slips provide Al3+ ions in aqueous solutions
- Thixotropic viscous behavior maintains thickness under gravity
Heating Cycle:
- gradual heating to oC
- 4-6 hour hold between oC
- 3 hour cooling to room temperature

15. Baccarat Ion-exchange Treatment: Results
Leaching studies done on treated crystal containing between 1%-40% PbO, all show greatly reduced leaching levels compared to untreated crystal
Secondary Ion Mass Spectroscopy (SIMS) shows a silico-aluminous layer of at least 20 nm; normally ranging between nm
Lead Leaching Test of Baccarat Surface Treated 30% PbO Crystal with a 4% acetic acid solution (pH=2.3) and with an alcohol solution (pH=3.5)
Time Elapsed (Months) 6 12 24 36 60
Lead Concentration (µg/L)
Acetic Acid
31.0
43.8
62.0 76 98
Alcohol 13
18.3
25.9
31.6 40

16. British Glass Microwave Assisted Ion Exchange
Overview:
Researches at British Glass investigated the use of different non-toxic metal ions (Al, Ti, Zr, Sr) for ceramic ion exchange slips using a microwave heat treatment
Crystal is pre-leached in 4% acetic acid at 90oC for 10 minutes.
Crystal is coated with ion exchange slip
Microwave exposure of 2.45 Ghz, 500 watt source for 10 minutes
Remove hardened slip from the crystal surface.

17. British Glass Microwave Assisted Ion Exchange (Cont.)
Advantages of Microwave Heating:
Crystal is transparent at microwave (Ghz) frequency
High absorption of radiation from ion-exchange slip at the crystal surface
Surface heating increases surface ion diffusion
Bulk crystal is not affected by the heat treatment
Oscillating electromagnetic wave can assist migration of charged ions

18. British Glass Microwave Assisted Ion Exchange: Results
All slips show superior performance to no treatment or acid washing in long term tests.
Prompted the refinement of the crystal surface treatment to reduce processing time and cost.
Refined method tested with a titanium ion exchange slip
Treatment
24 Hour
4% Acetic Acid
(ppb Pb)
4 Month
Control (no Treatment) Ti
600 10
(Not Recorded)
<25
XPS characterization of treated crystal shows a silica rich surface with small amounts of titania
SEM reveals no surface damage after treatment
Used 2h leach time and two stage 10min microwave treatment

19. Sol-Gel Method Hydrolysis of a Silicon Alkoxide:
(C2H5O)4-Si +H2O (C2H5O)3-Si-OH + C2H5OH (1)
Condensation Polymerization Reaction:
-Si-OH + OH-Si Si-O-Si- + H2O (2)
Coatings ≤ 2 µm Possible
Previous tests have shown no detectable lead leaching after coating, but results in unappealing optical qualities.

20. Chemical Vapor Deposition
CVD of thin films of phosphorous doped titania and zirconia for lead diffusion barrier
Tested By: Metaleurop Recherche and the Laboratory of Materials of the Polytechnic Institute, Grenoble
Source gas: Metal-organic precursors volatilized by ultrasonication at low pressures
Precursor gases mix in proper proportions with carrier gas
Pyrolysis of precursor gas take place at the surface of a heated crystal substrate
Heterogenous nucleation of film occurs at crystal surface

21. Chemical Vapor Deposition: Results
Process only tested on 2 cm2 flat crystal samples
- Control of film uniformity posses a problem for complex shapes
Low leach rates were reported (not replicated by further tests)
Thermal expansion of titania and zirconia are different than crystal
- Cooling the crystal after coating will cause strain at the interface
- Interface strain can lead to delamination

22. Schott Glass - PICVD Plasma Impulse Chemical Vapor Deposition (PICVD)
Developed By: Schott Glass
Primary Uses: Coating low melting point glass and polymer tubes and containers with quartz-like coatings
Microwave radiation is used to decompose precursor gas

23. Schott Glass – PICVD (Surface Coating Inspection)
Stage 1 - Two in-situ surface characterization methods
- Optical Plasma Emission
- Temperature
Stage 2 - Thickness controlled by online manipulation of gas flow, vacuum pressure, and microwave energy
Stage 3 – System Monitoring
- Automatic calibration of sensors
- Automatic data collection and archiving

24. Schott Glass – PICVD Durability and Leaching Results:
Comparison between Type 1 and Type 1 plus pharmaceutical glassware
Coating Maintained after Autoclaving Tests w/
Solution
Duration
(Hours)
Temperature
(°C)
0.1 M HCL 6
121
NaOH (pH=10) 1
3% EDTA (pH=4.5)
3% Citric acid

25. Surface Modification can…
Reduce lead leaching below Proposition 65 standards
Maintain the crystal’s original optical qualities
However,
Conventional heating near glass softening temperature is often needed for some processes
Processes rely on slow chemical reactions to remove lead from the crystal surface
Microwave processes are needed to reduce processing time
Lead removed from the crystal surface is a disposal issue

26. Surface Coating can…
Provide a lead-free diffusion barrier to lead migration
Be applied using a wide range of processing techniques at different temperatures
However,
Uniformity of the coating can present difficulties in certain coating processes
Incomplete coatings result in high lead leaching rates
Optical and mechanical properties of the surface coating must be similar to the properties of the coated crystal

27. References
Copley, G. J., & Kennedy, J. (1993a). British Glass, & Waterford Crystal. Microwave Surface Treatment For Lead Crystal Glassware. Paper presented at ICF Technical Exchange Conference, Pittsburgh, PA.
Copley, G. J., Dalton, D. A., & Glendenning, M. D. (1993b). British Glass. Full Lead Crystal: Report on Surface Modification. Paper presented at ICF Technical Exchange Conference, Waterford, Ireland.
Cornier, G., & Baccarat, Compagnie des Cristalleries de Baccarat. (1994). U.S. Patent No. 5,308,652. Washington, DC: U.S. Patent and Trademark Office.
Kear, B. H. (2007, Fall). Stuctural/Mechanical/Chemical Properties of Nanomaterials. MSE 14:635:401: Rutgers University.
Kliokis, J., Lehman, R. L., & Strange, D. J. (1997). Rutgers University: Center for Ceramics Research. Effects of Surface Treatments on Lead Migration from Lead Crystal Glassware. Paper presented at ICF Technical Exchange Conference, Estoril, Portugal.
Lehman, R. L., & Rabii, C. (1993a). Rutgers University: Center for Ceramics Research. The Effects of Surface Treatments on Lead Release of Lead Crystal Glass. Paper presented at ICF Technical Exchange Conference, Pittsburgh, PA.
Lehman, R. L. (1995). Rutgers University: Center for Ceramic Research. The Structure of Lead-Containing Silicate Glasses and Approaches to Improve Durability. Paper presented at ICF Technical Exchange Conference, Orrefors, Sweden.
Lehman, R. L., & Strange, D. J. (1996). Rutgers University: Center for Ceramics Research. Surface Treatment Of Lead Crystal: Optimized Stabilization of the Surface Layers of Lead Crystal Glassware. Paper presented at ICF Technical Exchange Conference, Stourbridge, UK.
Lehman, R. L. (2002). Rutgers University: Center for Ceramics Research. Lead Migration from Crystal Glassware: Developments From 12 Years of ICF TECs. Powerpoint preseneted at ICF Technical Exchange Conference, Waterford, Ireland.
OEHHA. (2007). OEHHA Proposition 65: Proposition 65 FAQs. Retrieved October, 12th, 2007, from Office of Environmental Health Hazard Assessment Website:
Perrier, E. (1993a). Metaleurop Recherche. Protective Coating For Crystal Glass. Paper presented at ICF Technical Exchange Conference, Pittsburgh, PA.
Potts, J. (1992). Lead Migration Reduction at Lenox. Paper presented at ICF Technical Exchange Conference, Colle Val d’Elsa, Italy.
Schott Glass (2007). Schott Type 1 Plus®: Container with a quartz-like inner surface [Pamphlet]. US: Schott Glass.