bj01\icf different colour why?.ppt 011030 the same pigment but different colour... bo jonson, glafo...

$: BJ01\ICF DIFFERENT COLOUR WHY?.PPT 011030 The same pigment but different colour... Bo Jonson, Glafo ICF, Siena, Nov 11-12, 2001 is it due to the lead content$
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?


...

if we need a paper!?

...


Hopefully you don’t need this kind

of paper today?


Background...

Previous (lead containing) glass formulations

give a specific colour when doped with a

pigment / pigment combination.


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.


Contents

- mechanism of colour generation

- a selection of performed experiments

- preliminary conclusions


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


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


Experimental procedure

- glass preparation

- recording of VIS-spectra, 300-900 mm

- attempts to make chemical analysis of various redox states of the pigment


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


octahedral tetrahedral

K2O-PbO-SiO2 K2O-CaO-SiO2 host glass Na2O-CaO-SiO2

Nickel in various host glasses


Conclusions

colour variation of nickel is due to the

structure / coordination polyhedra

sodium glass => tetrahedral: brownish

potassium glass => octahedral: purple


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!)


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 the same pigment but different colour... bo jonson, glafo...

Documents

specific colour

tetrahedralintensity

colour generation

pigment pigment combination

mos2 ni

host glass

glass formulations

lead content