BJ01\ICF DIFFERENT COLOUR WHY?.PPT 011030
The same pigment but
different colour...
Bo Jonson, GlafoICF, Siena, Nov 11-12, 2001
is it due to the lead content of the host glass?
WHY?
BJ01\ICF DIFFERENT COLOUR WHY?.PPT 011030
...
if we need a paper!?
...
BJ01\ICF DIFFERENT COLOUR WHY?.PPT 011030
Hopefully you don’t need this kind
of paper today?
BJ01\ICF DIFFERENT COLOUR WHY?.PPT 011030
Background...
Previous (lead containing) glass formulations
give a specific colour when doped with a
pigment / pigment combination.
BJ01\ICF DIFFERENT COLOUR WHY?.PPT 011030
but…
Introducing the same pigment
(combination) in an unleaded formula
might give rise to a different colour.
Correct?
Conclusion: The lead content of the host glass controls the colour.
BJ01\ICF DIFFERENT COLOUR WHY?.PPT 011030
Contents
- mechanism of colour generation
- a selection of performed experiments
- preliminary conclusions
BJ01\ICF DIFFERENT COLOUR WHY?.PPT 011030
Ionic colouration
Mechanism:
Colour is due to E
E depends on: coordination symetry (octahedral, tetrahedral)
Intensity of colour depends on the quantum mechanical premises (spin forbidden, spin allowed...)
=> the number of electrons
BJ01\ICF DIFFERENT COLOUR WHY?.PPT 011030
thus...the colour generated from a specific ion is controlled by
a) b)
A = • C • l Lamberth-Beers law
b) the redox state of the pigment...which is due to the melt oxygen activity, melting and refining / fining conditions
a) the co-ordination symmetry...which is due to the glass structure
BJ01\ICF DIFFERENT COLOUR WHY?.PPT 011030
BJ01\ICF DIFFERENT COLOUR WHY?.PPT 011030
Experimental procedure
- glass preparation
- recording of VIS-spectra, 300-900 mm
- attempts to make chemical analysis of various redox states of the pigment
BJ01\ICF DIFFERENT COLOUR WHY?.PPT 011030
BJ01\ICF DIFFERENT COLOUR WHY?.PPT 011030
Nickel
-0,05
0,00
0,05
0,10
0,15
0,20
0,25
0,30
300 400 500 600 700 800 900
nm
Ab
s
Ni med molybdensulfid (1)
Ni med molybdensulfid (2)
Ni med antiomonoxid
Ni med MoS2
Results...Nickel refined with MoS2 and Sb2O3
Ni with MoS2
Ni with MoS2 (1) Ni
with MoS2 (2)
Ni with Sb2 O3
BJ01\ICF DIFFERENT COLOUR WHY?.PPT 011030
octahedral tetrahedral
K2O-PbO-SiO2 K2O-CaO-SiO2 host glass Na2O-CaO-SiO2
Nickel in various host glasses
BJ01\ICF DIFFERENT COLOUR WHY?.PPT 011030
BJ01\ICF DIFFERENT COLOUR WHY?.PPT 011030
BJ01\ICF DIFFERENT COLOUR WHY?.PPT 011030
BJ01\ICF DIFFERENT COLOUR WHY?.PPT 011030
BJ01\ICF DIFFERENT COLOUR WHY?.PPT 011030
Conclusions
colour variation of nickel is due to the
structure / coordination polyhedra
sodium glass => tetrahedral: brownish
potassium glass => octahedral: purple
BJ01\ICF DIFFERENT COLOUR WHY?.PPT 011030
Colour variation of other investigated transition
elements is due to the redox distribution.
The redox distribution depends on the used
refining / fining agent.
(Older PbO glasses normally contained As2O3!)
BJ01\ICF DIFFERENT COLOUR WHY?.PPT 011030
Reducing power of the fining agents investigated seems to be:
(MoS2) > Sb2O3 > As2O3 > CeO2
however, with some exceptions to the effect of MoS2.
BJ01\ICF DIFFERENT COLOUR WHY?.PPT 011030
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