Slide 1

QUANTIFICATION OF SMITHING ACTIVITIES
BASED ON THE INVESTIGATION OF SLAG
AND OTHER MATERIAL REMAINS
Vincent Serneels
Sébastien Perret

Mineralogy and Petrography
Departement of Geoscience
University of Fribourg
Switzerland

[email protected]
[email protected]
www.unifr.ch/mineral/archmet


Slide 2

The Production Line of the Ancient Iron Metallurgy

Production line :
Sequence of technical steps from the raw material to
the finished object.

V. Serneels, S. Perret

Mineralogy and Petrography - University of Fribourg


Slide 3

The Production Line of the Ancient Iron Metallurgy
Natural ore

Extraction
Refuse
Extracted ore

V. Serneels, S. Perret

Mineralogy and Petrography - University of Fribourg


Slide 4

The Production Line of the Ancient Iron Metallurgy
Natural ore

Extraction
Refuse
Extracted ore

Processing

Refuse
Concentrated ore

V. Serneels, S. Perret

Mineralogy and Petrography - University of Fribourg


Slide 5

The Production Line of the Ancient Iron Metallurgy
Natural ore

Extraction
Refuse
Extracted ore

Processing

Refuse
Concentrated ore

Reduction
Slag
Raw iron

Direct method of reduction :
• Bloomery process
• Solid state
• FeO + CO

V. Serneels, S. Perret



Fe + CO2

Mineralogy and Petrography - University of Fribourg


Slide 6

The Production Line of the Ancient Iron Metallurgy
Natural ore

Extraction
Refuse
Extracted ore

Processing

Refuse
Concentrated ore

Reduction
Slag
Raw iron

Direct method of reduction :
• Bloomery process
• Solid state
• FeO + CO  Fe + CO2

V. Serneels, S. Perret

Mineralogy and Petrography - University of Fribourg


Slide 7

The Production Line of the Ancient Iron Metallurgy
Natural ore

Extraction
Refuse
Extracted ore

Processing

Refuse
Concentrated ore

Reduction
Slag
Raw iron

• Welding

Smithing
Slag
Finished object

V. Serneels, S. Perret

• Plastic deformation
(hammering / heating)
• Heat treatment
(annealing / quenching)
• Control of oxydation / carburization
Mineralogy and Petrography - University of Fribourg


Slide 8

Smithing
Smithing depends on :

Physical characteristics :

• Quality of the metal

• Compact / homogenous
bar iron
• Uncompacted / heterogeneous
bloom iron
• Small pieces
scrap

Chemistry :
• % carbon
• % other elements :
P, S, N, Mn, Ni, 0...
V. Serneels, S. Perret

Mineralogy and Petrography - University of Fribourg


Slide 9

Smithing
Smithing depends on :

Kind of object :

• Quality of the metal

• Simple

nail

• Complex

composite blade
iron + steel

• Type of object to
produce

Size of object :
• Small

nail
knife
axe

• Large

anchor

10 g
100 g
1000 g
10000 g

Sharpening, polishing, decoration

V. Serneels, S. Perret

Mineralogy and Petrography - University of Fribourg


Slide 10

Smithing
Smithing depends on :

Qualification :

• Quality of the metal

• Heat treatments

• Type of object to
produce
• Know-how of the
smith

V. Serneels, S. Perret

- annealing
- quenching
• Welding
• etc...

Mineralogy and Petrography - University of Fribourg


Slide 11

Smithing slags
Contribution to slag
formation :

Formation of a slag rich in iron
oxides :

• Hot oxidation

 FeO

• Related to time / temperature
• Related to the size of the section
V. Serneels, S. Perret

Mineralogy and Petrography - University of Fribourg


Slide 12

Smithing slags
Contribution to slag
formation :

Formation of a slag rich in iron
oxides :

• Hot oxidation

 FeO

• Related to time / temperature
• Related to the size of the section
V. Serneels, S. Perret

Mineralogy and Petrography - University of Fribourg


Slide 13

Smithing slags
Contribution to slag
formation :

Formation of a slag with iron
particles :

• Hot oxidation

 FeO
• Poorly consolidated
metal
 Fe

V. Serneels, S. Perret

Mineralogy and Petrography - University of Fribourg


Slide 14

Smithing slags
Contribution to slag
formation :

Formation of a slag rich in silica :

• Hot oxidation

 FeO
• Poorly consolidated
metal
 Fe
• Use of flux
 SiO2

V. Serneels, S. Perret

Mineralogy and Petrography - University of Fribourg


Slide 15

Smithing slags
Contribution to slag
formation :

Other elements participate with
various chemical elements :

• Hot oxidation

 FeO
• Poorly consolidated
metal
 Fe
• Use of flux
 SiO2

• Other effects
 K2O, CaO,
SiO2 , Al2O3...

V. Serneels, S. Perret

Mineralogy and Petrography - University of Fribourg


Slide 16

Smithing slags

PCB : Plano-convex
bottom slags
• Characteristic
morphology
• Most typical
smithing residue

V. Serneels, S. Perret

Mineralogy and Petrography - University of Fribourg


Slide 17

Smithing slags

PCB : Plano-convex
bottom slags
• Characteristic
morphology

• 1 cooling structure
 Formed between lighthing and
extinguishing of the fire

• Most typical
smithing residue

•

1 unit of work

 1 day ?

V. Serneels, S. Perret

Mineralogy and Petrography - University of Fribourg


Slide 18

Smithing slags
Variability of PCB slags :
• Dimensions and
weight
Ø

h

weight

5 cm

1 cm

50 gr

Normal

15 cm

3 cm

300 gr

Large

30 cm

10 cm

3000gr

Small

As a general rule :
The weight is proportional to the
quantity of work

V. Serneels, S. Perret

Mineralogy and Petrography - University of Fribourg


Slide 19

Smithing slags
Variability of PCB slags :
• Dimensions and
weight

• Shape

V. Serneels, S. Perret

Mineralogy and Petrography - University of Fribourg


Slide 20

Smithing slags
Variability of PCB slags :
• Dimensions and
weight

• Shape

V. Serneels, S. Perret

Mineralogy and Petrography - University of Fribourg


Slide 21

Smithing slags
Variability of PCB slags :
• Dimensions and
weight

• Shape
• Composition

V. Serneels, S. Perret

Mineralogy and Petrography - University of Fribourg


Slide 22

Smithing slags

V. Serneels, S. Perret

Mineralogy and Petrography - University of Fribourg


Slide 23

Smithing slags

PCB : Plano-convex bottom slags
• Weight of PCB

=

quantity of work

• Composition of PCB

=

Type of work

Assembly of PCBs



activity of a workshop

V. Serneels, S. Perret

Mineralogy and Petrography - University of Fribourg


Slide 24

Examples of PCB assemblies from Switzerland

V. Serneels, S. Perret

Mineralogy and Petrography - University of Fribourg


Slide 25

Examples of PCB assemblies from Switzerland

V. Serneels, S. Perret

Mineralogy and Petrography - University of Fribourg


Slide 26

Vincent Serneels
Sébastien Perret

Mineralogy and Petrography
Departement of Geoscience
University of Fribourg
Switzerland

[email protected]
[email protected]
www.unifr.ch/mineral/archmet