Pigments through the Ages - Technical Information

A painted swatch of Smalt:

About the chemical structure:

Chemical name:	potassium glass containing cobalt
Formula:	SiO₂(65%) + K₂0 (15%) + Al₂O₃(5%) + CoO (10%)
Crystal system:	glass
Refractive index:	1.46 - 1.55

How can you identify Smalt?

Imaging:

n/a

Analytics:

It's identified by means of FTIR and Raman.

Raman spectra: University College London;

FTIR spectra: IRUG

Usage and handling:

Permanence:	Toxicity:
Lightfast:good. degradation processes: like all glass based pigments, it is stable unless improperly made, and is better in aqueous media and lime for fresco. Anyway, smalt is known to fade.	moderately toxic. Smalt contains cobalt, which can be toxic if inhaled or ingested. Care should be used in handling the dry powder pigment to avoid inhaling the dust. May be harmful if swallowed. May be harmful by breathing dusts or mists. MSDS: Natural pigments

Permanence:

Toxicity:

Lightfast:good.

degradation processes: like all glass based pigments, it is stable unless improperly made, and is better in aqueous media and lime for fresco. Anyway, smalt is known to fade.

moderately toxic. Smalt contains cobalt, which can be toxic if inhaled or ingested. Care should be used in handling the dry powder pigment to avoid inhaling the dust. May be harmful if swallowed. May be harmful by breathing dusts or mists.

MSDS: Natural pigments

Literature:

Binger, H., Das Blaupigment Smalte, Restauro, 1, 1996, p. 36-39
Artists’ Pigments. A Handbook of Their History and Characteristics, Vol. 2: A. Roy (Ed.) Oxford University Press 1993, p. 113-130