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