ALTARPIECE OF SAINT PETER

SCIENTIFIC ANALYSES 

Chemical analysis:

- Support layer: decorated with several layers (30-500 µm) of calcium carbonate.

- Linseed oil based polychrome decoration, except for blacks and blues which are tempera and glue.

- Brownish-grey brocade filler made of beeswax, fir resin and linseed oil mixed with pigments. Traces of minium, clays, white lead and carbon black.

- Yellow and brown mordant (oil and yellow lead) with added white lead, clays and carbon black.

- Vegetation: several layers of green (verdigris, white lead and yellow clay), gold fragments and velatura-finished verdigris.

- Flesh tones: Fine layers of colour based on white lead and vermillion with velatura of ochre-coloured clays and yellow lead in the darkest spots.

- Glass shards of potassium and calcium with traces of iron and manganese agglutinated in a translucent layer of linseed oil and fir resin (300 µm) applied to a base of carbon black, red earth and traces of calcite and azurite.*

*Data provided by Restauraciones Siglo XXI, 2002