Journal of Archaeology in the Low Countries 3-1 (November 2011)Janneke Nienhuis; Jilt Sietsma; Stijn Arnoldussen: The Production Process and Potential Usage of Bronze Geistingen Axes

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3.1 Composition

The results concerning the composition of the two Geistingen axes, determined with NRCA (Postma et al. 2005a; 2011/in press; personal communication 2010), XRF and EPMA are summarised in table 1 and illustrated in figure 4.

Table 1 Average compositions (in at%) of two Geistingen axes determined with NRCA, XRF and EPMA.

Axe		Pb	Sn	Sb	As	Fe	Ni	S	Ag	Cu (by balance)

AC20	Mean	0.21	9	1.4	0.72	0.4	2	0.95	0.378	85
	error	0.01	2	0.2	0.01	0.2	1	0.06	0.003	3

BH76	Mean	0.4	0.62	4	2.9	0.2	6	1.26	0.605	84
	error	0.3	0.08	1	0.1	0.1	2	0.09	0.004	4

Figure 4 Compositions (in at%) of two Geistingen axes determined with NRCA, XRF and EPMA.

Table 1 and figure 4 show the relevance of using three complementary techniques to determine the chemical compositions. NRCA is able to quantify silver while EPMA is in this case the only technique that measures sulphur. Both elements are important in deducing the raw material used for production (see sections 3.2 and 3.3). NRCA, XRF and EPMA all confirm the presence of the main alloying elements tin, antimony and nickel. The main differences are seen in the number of elements and their percentages, which originate from the technical specifications and limitations of the techniques used (see section 2.2).

Due to systematic instrumental uncertainties for each technique that cannot be accurately determined, a larger variation in the concentration values is found than expected on the basis of the statistical errors per technique. Therefore, for every element detected with more than one technique, the arithmetic mean is calculated and the corresponding error is calculated by using the least squares method. The use of these complementary analytical methods thus provides a more accurate determination of the composition than by using only one.

The results lead to the conclusion that AC20 can be identified as a binary copper-tin bronze with 9 at% tin, while BH76 is essentially a ternary copper-antimony-nickel alloy with 4 at% antimony and 6 at% nickel.

Comparing these numbers with known compositions from functional and contemporary axes can highlight the differences and help form a hypothesis on the function of Geistingen axes. Only a modest corpus of metal analyses on Late Bronze Age axe types is available for the area under study (table 2). The corpus mostly consists of axes of the Plainseau and Geistingen types and very few other types (Niedermaas, Armorican, Wesseling; Butler 2003/2003) are represented. Moreover, the quality of the analytical techniques is varied (chemical extraction versus XRF/EPMA). Nonetheless, the data allow characterising the composition of certain axe types. The (functional) axes of the Plainseau-type can be roughly characterised as copper containing tin (2-10 at%) and lead (2-7 at%) with virtually no other elements present (Van Impe 1994; Wouters 1994, 42). The Geistingen axes studied as part of the SAM series can be characterised as copper with 0.5-5.8 at% tin, 1.8-2.9 at% arsenic, 0.2-2.3 at% antimony and low (

Table 2 Metal composition of Late Bronze Age socketed axe types, measured using different analytical techniques.

As		Sb		Ni		Fe		References		Remarks
0,036		0,001		0,001		0,001		Wouters 1994, 41 tab. 1;		Pres. Niedermaas-type axe; average of 5 measurements
								Van Impe & Creemers 1993;
								Butler & Steegstra 2002/2003, 269-271.
0,031		0,001		0,08		0,001		Wouters 1994, 41 tab. 1;		Pres. Niedermaas-type axe; average of 6 measurements
								Van Impe & Creemers 1993;
								Butler & Steegstra 2002/2003, 269-271.
0,054		0,001		0,001		0,001		Wouters 1994, 41 tab. 1;		Pres. Niedermaas-type axe; average of 5 measurements
								Van Impe & Creemers 1993;
								Butler & Steegstra 2002/2003, 269-271.
0,009		0,001		0,002		0,001		Wouters 1994, 42 tab. 2;		Axe of 'Plainseau' type
								Van Impe 1994;
								Butler & Steegstra 2002/2003, 280-282
0,007		0,001		0,057		0,082		Wouters 1994, 42 tab. 2;		Axe of 'Plainseau' type
								Van Impe 1994;
								Butler & Steegstra 2002/2003, 280-282
0,007		0,001		0,001		0,89		Wouters 1994, 42 tab. 2;		Axe of 'Plainseau' type
								Van Impe 1994;
								Butler & Steegstra 2002/2003, 280-282
0,01		0,001		0,022		1,51		Wouters 1994, 42 tab. 2;		Axe of 'Plainseau' type
								Van Impe 1994;
								Butler & Steegstra 2002/2003, 280-282
0,009		0,001		0,02		0,35		Wouters 1994, 42 tab. 2;		Axe of 'Plainseau' type
								Van Impe 1994;
								Butler & Steegstra 2002/2003, 280-282
0,009		0,001		0,035		0,19		Wouters 1994, 42 tab. 2;		Axe of 'Plainseau' type
								Van Impe 1994;
								Butler & Steegstra 2002/2003, 280-282
0,001		0,001		0,006		0,16		Wouters 1994, 42 tab. 2;		Axe of 'Plainseau' type
								Van Impe 1994;
								Butler & Steegstra 2002/2003, 280-282
0,009		0,001		0,006		0,089		Wouters 1994, 42 tab. 2;		Axe of 'Plainseau' type
								Van Impe 1994;
								Butler & Steegstra 2002/2003, 280-282
0,008		0,001		0,012		0,007		Wouters 1994, 42 tab. 2;		Axe of 'Plainseau' type
								Van Impe 1994;
								Butler & Steegstra 2002/2003, 280-282
0,008		0,001		0,001		0,39		Wouters 1994, 42 tab. 2;		Axe of 'Plainseau' type
								Van Impe 1994;
								Butler & Steegstra 2002/2003, 280-282
0,001		0,001		0,06		0,31		Wouters 1994, 42 tab. 2;		Axe of 'Plainseau' type
								Van Impe 1994;
								Butler & Steegstra 2002/2003, 280-282
0,01		0,001		0,02		0,001		Wouters 1994, 42 tab. 2;		Axe of 'Plainseau' type
								Van Impe 1994;
								Butler & Steegstra 2002/2003, 280-282
0,01		0,001		0,001		0,001		Wouters 1994, 42 tab. 2;		Axe of 'Plainseau' type
								Van Impe 1994;
								Butler & Steegstra 2002/2003, 280-282
0,011		0,001		0,001		0,001		Wouters 1994, 42 tab. 2;		Axe of 'Plainseau' type
								Van Impe 1994;
								Butler & Steegstra 2002/2003, 280-282
0,003		0,001		0,001		0,001		Wouters 1994, 42 tab. 2;		Axe of 'Plainseau' type
								Van Impe 1994;
								Butler & Steegstra 2002/2003, 280-282
0,011		0,001		0,001		0,001		Wouters 1994, 42 tab. 2;		Axe of 'Plainseau' type
								Van Impe 1994;
								Butler & Steegstra 2002/2003, 280-282
0,011		0,001		0,001		0,001		Wouters 1994, 42 tab. 2;		Axe of 'Plainseau' type
								Van Impe 1994;
								Butler & Steegstra 2002/2003, 280-282
0,014		0,001		0,001		0,001		Wouters 1994, 42 tab. 2;		Axe of 'Plainseau' type
								Van Impe 1994;
								Butler & Steegstra 2002/2003, 280-282
0,01		0,001		0,001		0,001		Wouters 1994, 42 tab. 2;		Axe of 'Plainseau' type
								Van Impe 1994;
								Butler & Steegstra 2002/2003, 280-282
0,01		0,001		0,001		0,001		Wouters 1994, 42 tab. 2;		Axe of 'Plainseau' type
								Van Impe 1994;
								Butler & Steegstra 2002/2003, 280-282
0,01		0,001		0,001		0,001		Wouters 1994, 42 tab. 2;		Axe of 'Plainseau' type
								Van Impe 1994;
								Butler & Steegstra 2002/2003, 280-282
0,012		0,001		0,001		0,001		Wouters 1994, 42 tab. 2;		Axe of 'Plainseau' type
								Van Impe 1994;
								Butler & Steegstra 2002/2003, 280-282
0,01		0,001		0,001		0,001		Wouters 1994, 42 tab. 2;		Axe of 'Plainseau' type
								Van Impe 1994;
								Butler & Steegstra 2002/2003, 280-282
0,011		0,001		0,001		0,001		Wouters 1994, 42 tab. 2;		Axe of 'Plainseau' type
								Van Impe 1994;
								Butler & Steegstra 2002/2003, 280-282
0,009		0,001		0,001		0,001		Wouters 1994, 42 tab. 2;		Axe of 'Plainseau' type
								Van Impe 1994;
								Butler & Steegstra 2002/2003, 280-282
0,01		0,001		0,001		0,001		Wouters 1994, 42 tab. 2;		Axe of 'Plainseau' type
								Van Impe 1994;
								Butler & Steegstra 2002/2003, 280-282
0,01		0,001		0,001		0,001		Wouters 1994, 42 tab. 2;		Axe of 'Plainseau' type
								Van Impe 1994;
								Butler & Steegstra 2002/2003, 280-282
0,01		0,001		0,001		0,001		Wouters 1994, 42 tab. 2;		Axe of 'Plainseau' type
								Van Impe 1994;
								Butler & Steegstra 2002/2003, 280-282
0,01		0,001		0,001		0,001		Wouters 1994, 42 tab. 2;		Axe of 'Plainseau' type
								Van Impe 1994;
								Butler & Steegstra 2002/2003, 280-282
0,01		0,001		0,001		0,001		Wouters 1994, 42 tab. 2;		Axe of 'Plainseau' type
								Van Impe 1994;
								Butler & Steegstra 2002/2003, 280-282
0,01		0,001		0,001		0,001		Wouters 1994, 42 tab. 2;		Axe of 'Plainseau' type
								Van Impe 1994;
								Butler & Steegstra 2002/2003, 280-282
0,011		0,001		0,001		0,001		Wouters 1994, 42 tab. 2;		Axe of 'Plainseau' type
								Van Impe 1994;
								Butler & Steegstra 2002/2003, 280-282
0,01		0,001		0,001		0,001		Wouters 1994, 42 tab. 2;		Axe of 'Plainseau' type
								Van Impe 1994;
								Butler & Steegstra 2002/2003, 280-282
0,01		0,001		0,001		0,001		Wouters 1994, 42 tab. 2;		Axe of 'Plainseau' type
								Van Impe 1994;
								Butler & Steegstra 2002/2003, 280-282
0,01		0,001		0,001		0,001		Wouters 1994, 42 tab. 2;		Axe of 'Plainseau' type
								Van Impe 1994;
								Butler & Steegstra 2002/2003, 280-282
0,011		0,001		0,001		0,001		Wouters 1994, 42 tab. 2;		Axe of 'Plainseau' type
								Van Impe 1994;
								Butler & Steegstra 2002/2003, 280-282
0,001		0,001		0,001		0,001		Wouters 1994, 42 tab. 2;		Axe of 'Plainseau' type
								Van Impe 1994;
								Butler & Steegstra 2002/2003, 280-282
0,012		0,001		0,001		0,001		Wouters 1994, 42 tab. 2;		Axe of 'Plainseau' type
								Van Impe 1994;
								Butler & Steegstra 2002/2003, 280-282
0,012		0,001		0,001		0,001		Wouters 1994, 42 tab. 2;		Axe of 'Plainseau' type
								Van Impe 1994;
								Butler & Steegstra 2002/2003, 280-282
0,011		0,001		0,001		0,43		Wouters 1994, 42 tab. 2;		Axe of 'Plainseau' type
								Van Impe 1994;
								Butler & Steegstra 2002/2003, 280-282
0,009		0,001		0,001		0,001		Wouters 1994, 42 tab. 2;		Axe of 'Plainseau' type; average of 2 measurements
								Van Impe 1994;
								Butler & Steegstra 2002/2003, 280-282
0,011		0,001		0,001		0,001		Wouters 1994, 42 tab. 2;		Axe of 'Plainseau' type
								Van Impe 1994;
								Butler & Steegstra 2002/2003, 280-282
0,01		0,001		0,001		0,56		Wouters 1994, 42 tab. 2;		Axe of 'Plainseau' type
								Van Impe 1994;
								Butler & Steegstra 2002/2003, 280-282
0,009		0,001		0,001		0,001		Wouters 1994, 42 tab. 2;		Axe of 'Plainseau' type
								Van Impe 1994;
								Butler & Steegstra 2002/2003, 280-282
0,008		0,001		0,001		0,001		Wouters 1994, 42 tab. 2;		Axe of 'Plainseau' type
								Van Impe 1994;
								Butler & Steegstra 2002/2003, 280-282
0,008		0,001		0,001		0,001		Wouters 1994, 42 tab. 2;		Axe of 'Plainseau' type
								Van Impe 1994;
								Butler & Steegstra 2002/2003, 280-282
0,009		0,001		0,001		0,001		Wouters 1994, 42 tab. 2;		Axe of 'Plainseau' type
								Van Impe 1994;
								Butler & Steegstra 2002/2003, 280-282
0,01		0,001		0,001		0,001		Wouters 1994, 42 tab. 2		Axe of 'Plainseau' type; pres. part of Heppeneert hoard
0,01		0,001		0,001		0,001		Wouters 1994, 42 tab. 2		Axe of 'Plainseau' type; pres. part of Heppeneert hoard
n.a.		n.a.		n.a.		n.a.		Van Impe 1995/1996, 31		Axe of 'Plainseau' type
n.a.		n.a.		n.a.		n.a.		Van Impe 1995/1996, 31		Axe of 'Plainseau' type
0,08		0,08		0,05		n.a.		Verlaeckt 1996, 88-89		Axe of 'Plainseau' type; Ag 0,07
1,18		0,56		0,07		n.a.		Verlaeckt 1996, 90		Axe of 'Plainseau' type; Bi 0,1
0,18		n.a.		0,25		0,18		Verlaeckt 1996, 90		Axe of 'Plainseau' type; Bi 0,1
0,06		0,09		0,02		n.a.		Verlaeckt 1996, 109		Axe of 'Plainseau' type; Bi 0,002; Ag 0,05
0,35		<0,62		0,12		0,39		Verlaeckt 1996, 119		Axe of 'Plainseau' type?; Bi 0,06
0,316		0,596		0,161		0,96		Verlaeckt 1996, 119		Axe of 'Plainseau' type?; Bi 0,046
0,07		0,15		0,1		0,08		Verlaeckt 1996, 120		Axe of 'Plainseau' type?; Bi 0,004
1,5		0,7		0,25		0,01		Verlaeckt 1996, 120		Axe of 'Plainseau' type?; Bi 0,015
1		0,8		0,25		0,002		Verlaeckt 1996, 103		Local type (cast in Heusden mould?)
0,535		1,26		1		0,072		Verlaeckt 1996, 90		Axe of type Sompting
2		1		0,25		0,035		Verlaeckt 1996, 106		Axe related to type Sompting ('Atlantic')
1		1		0,35		0,1		Verlaeckt 1996, 106		Axe related to type Sompting ('Atlantic')
0,55		0,15		0,06		0,03		Verlaeckt 1996, 120		Axe related to type Sompting ('Atlantic'); Bi 0,01
0,56		n.a.		0,66		0,23		Verlaeckt 1996, 101		Atlantic'?
3,3		4,1		1,9		n.a.		Kibbert 1984, 214;		Axe of type Geistingen; Co 0,06
								Junghans et al.1960-1974 (SAM 16559)
0,55		2,6		0,5		n.a.		Kibbert 1984, 214;		Axe of type Geistingen, Co 0,04
								Junghans et al.1960-1974 (SAM 16552)
2,1		0,046		0,03		n.a.		Kibbert 1984, 214;		Axe of type Geistingen; Co 0,08
								Junghans et al.1960-1974 (SAM 21612)
1,7		2,7		1,2		n.a.		Kibbert 1984, 214;		Axe of type Geistingen, Co 0,26
								Junghans et al.1960-1974 (SAM 16560)
1,07		2,17		1,97		n.a.		Postma et al. in press table 1;		Axe of type Geistingen
								Butler & Steegstra 2002/2003, 305
1		3,62		4,47		n.a.		Postma et al. in press table 1;		Axe of type Geistingen
								Butler & Steegstra 2002/2003, 305
2,36		4,27		7,58		n.a.		Postma et al. in press table 1;		Axe of type Geistingen
								Wielockx 1986
2,69		4,47		7,73		n.a.		Postma et al. in press table 1;		Axe of type Geistingen
								Wielockx 1986
3,09		4,65		6,59		n.a.		Postma et al. in press table 1;		Axe of type Geistingen; XRF&EPMA
								Wielockx 1986		measurements done (this study)
3,05		5,54		7,83		n.a.		Postma et al. in press table 1;		Axe of type Geistingen
								Wielockx 1986
1,97		3,21		4,3		n.a.		Postma et al. in press table 1		Axe of type Geistingen
2,39		2,66		3,95		n.a.		Postma et al. in press table 1		Axe of type Geistingen
1,24		2,4		6,53		n.a.		Postma et al. in press table 1;		Axe of type Geistingen
								Butler & Steegstra 2002/2003, 309
1,19		1,76		1,5		n.a.		Postma et al. in press table 1;		Axe of type Geistingen
								Butler & Steegstra 2002/2003, 309
0,62		0,87		<0.90		n.a.		Postma et al. in press table 1;		Axe of type Geistingen
								Butler & Steegstra 2002/2003, 309
0,82		2,21		<2.5		n.a.		Postma et al. in press table 1;		Axe of type Geistingen; XRF&EPMA
								Butler & Steegstra 2002/2003, 305		measurements done (this study)
traces		n.a.		n.a.		n.a.		Jacobsen 1904, 18		Axe of 'Plainseau' type; Ag 0,17
traces		n.a.		n.a.		1,5		Jacobsen 1904, 18		Axe of unclear (Niedermaas) type; Ag 0,19
n.a.		n.a.		n.a.		0,77		Jacobsen 1904, 20		Axe of 'Plainseau' type
n.a.		n.a.		n.a.		1,05		Jacobsen 1904, 24		Axe of Armorican type?
n.a.		n.a.		n.a.		1,05		Jacobsen 1904, 39		Axe of Armorican type?; S 0,275
2,35		3,4		0,19		1,99		Verlaeckt 1996, 109		Axe of 'Plainseau' / 'Atlantic' type?; Bi 0,11 (Armorican?)
0,15		0,09		0,02		0,08		Verlaeckt 1996, 87-88		Axe of Armorican type (Tréhou); Ag 0,06
0,46		0,11		0,02		0,16		Verlaeckt 1996, 93		Axe of Armorican type (Tréhou); Bi 0,71
0,39		0,37		0,04		n.a.		Verlaeckt 1996, 89		axe of Armorican type (Plurien); Bi 0,32
0,48		0,29		0,03		0,07		Verlaeckt 1996, 89		Axe of Armorican type (Plurien); Bi 0,35
0,59		<0,17		0,02		0,54		Verlaeckt 1996, 97		Axe of Armorican type (Plurien); Bi 0,22
0,53		0,23		0,06		0,11		Verlaeckt 1996, 119		Axe of Armorican type (Plurien); Bi 0,19
0,29		n.a.		0,03		0,11		Verlaeckt 1996, 101		Axe of Armorican type (Plurien); Bi 1,01
0,31		n.a.		0,05		0,18		Verlaeckt 1996, 89		Axe of Armorican type (Couville); Bi 0,32
traces		n.a.		n.a.		0,35		Jacobsen 1904, 43		Axe of type 'winged with biconical collar'
n.a.		n.a.		n.a.		0,315		Jacobsen 1904, 44		Axe of linear faceted type
n.a.		n.a.		n.a.		0,507		Jacobsen 1904, 44-45		Axe of type Wesseling
1,1		1,9		0,55		n.a.		Kibbert 1984, 168-170; 214		Axe of type Amelsbüren; Bi 0,027; Ag 0, 58
0,29		0,3		0,14		n.a.		Kibbert 1984, 168-170; 214		Axe of type Amelsbüren; Bi 0,033; Ag 0,22
0,42		0,46		0,17		n.a.		Kibbert 1984, 168-170; 214		Axe of type Amelsbüren; Bi 0,025; Ag 0,3
0,33		0,53		0,13		n.a.		Kibbert 1984, 168-170; 214		Axe of type Amelsbüren; Bi 0,022; Ag 0,36
0,95	.	6,4	.	0,65	.	0,01	.	Craddock 1979, 380 table 2	.	Socketed looped axe of continental type

When drawing comparisons with the data available for axe (type)s known to be functional (see table 2), Geistingen axes differ in a number of ways, although there are also some similarities. First, the tin content of the Geistingen axes falls in the range present in several Plainseau and Armorican axes, but since there is such a wide margin (5 at% antimony or >4 at% arsenic, is the result of the re-melting of scrap bronze (Curtis & Kruszyński 2002, 91). Axe BH76 from the Geistingen depot shows such a combination (see table 1). However, sometimes antimony is seen as an intentional replacement for tin (Craddock 1979, 380). This indicates that the combination of tin and antimony seen in axe BH76 is the result of intentional addition of only antimony. This however does not explain the high nickel and arsenic content found, so it is argued that re-melting in this case seems more likely because of the additional elements present. When looking at the arsenic content of the axes shown in table 2, a dichotomy is seen: the Geistingen axes contain more than 1 at% (up to 3 at%) arsenic, while the content of all other axes measured is (much) less than 1 at%. Next to making the copper appear more silvery, addition of more than 2 at% arsenic will make the object harder without loss of integrity (Lechtman 1996, 506; 509; Junk 2003, 23; 24). The same arguments apply to nickel. Furthermore, the Geistingen axes contain 1-7 at% nickel, while other axes contain (much) less than 1 at%. The effect of nickel as an alloying element is comparable to that of arsenic, resulting in good cold and hot working properties of the alloy (Cheng & Schwitter 1957, 351). The amount of lead found in the Geistingen axes is lower than 1 at% and the majority of the axes listed in table 2 contain more than 1 at%. The addition of less than 1 at% lead to copper will lead to increased fluidity of the melt, making the casting of hollow shapes more easy (Craddock 1979, 383). Adding more than 1 at% will significantly reduce the melting point of copper, with a reduction of almost 200 °C for a bronze containing 18 at% lead (Craddock 1979, 383). However, upon solidification of a leaded copper alloy, the lead will form insoluble globules that are dispersed throughout the microstructures. Increasing the lead content will increase the size of these globules, which will cause major areas of weakness. Therefore, bronze objects containing large amounts (>1 at%) of lead might be cast as ingots and not intended to be functional objects (Craddock 1979, 383). In case of the Geistingen axes, lead is not intentionally added to make the axe unusable since its concentration is below 1 at%. Its presence can however be attributed to the reduction of the melting point and the increase of fluidity. Another element found in more than 1 at% in Geistingen axes but not, or in less than 1 at%, is antimony (see table 2). One exception is the socketed looped axe of continental type (Craddock 1979, 380). In general, the addition of antimony to copper will lower the melting temperature and in amounts over 0.5 at% will slightly increase toughness and ductility, as well as the hardness of copper (Junk 2003, 26; 28). However, in percentages over approximately 4% the result is a brittle alloy (Charles 1980 in Moorey 1999, 241). The Geistingen axes analysed in this research contain respectively 1.4 at% and 4 at% (see table 1), which means one of them is on the verge of being unusable because of brittleness. These numbers indicate that the antimony was either added on purpose (perhaps to make the axes less suitable as tools or weapons), or the presence of the element could not be controlled, i.e. the ore or scrap contained large amounts of antimony. In both cases, the result is that the finished Geistingen axe could not have been functional on compositional grounds as well as the low weight of the objects.

Therefore, the combination of >1 at% antimony, >1 at% Ni and >1 at% As in the Geistingen axes has no counterpart in the composition of any of the contemporary axes in table 2. This sets the Geistingen axes even further apart from other socketed axes.