Investigation of coloured lead glass glitter from an early eighteenth century material collection, Cambridge, by electron microscopy/energy dispersive X-ray analysis

Heritage Science

Table 2 Results of the EDX analysis for alkali lead glasses, samples I/3 (blue), I/39 (colourless), I/60 (turquoise) and I/62 (blackish purple), amounts are given in wt%, nd —element was not detected, x—element was detected but not quantified. Usually the composition was very homogenious and glassy, spots with a unusual compostion are marked in second header line

Wt%	Blue flakes—I/3					White flakes—I/39			Ash coloured flakes—I/60		Blackish purple flakes—I/62
			Dark zone									Metal	Metal			Silica
	b1	b2	b3	c1	c2	b1	b2	b3	b1	b2	b1	b2	b3	b4	b5	b6
Na₂O	8.8	7.9	6.3	4.8	4.5	6.8	3.8	3.6	9.5	9.8	4.8	nd	nd	4.5	3.9	1.1
MgO	3.0	2.4	2.6	2.0	2.2	1.4	1.2	1.3	3.2	3.0	1.8	1.5	1.8	1.4	x	1.6
Al₂O₃	x	x	x	x	x	nd	x	nd	x	x	x	nd	nd	x	1.0	nd
SiO₂	56	56	59	56	56	56	52	46	58	58	39	1.7	1.7	36	35	80
Cl	x	x	x	x	x	x	x	x	x	x	nd	nd	nd	nd	nd	nd
K₂O	4.0	4.0	4.5	9.4	9.4	4.3	5.3	7.1	4.1	4.4	3.8	nd	nd	3.4	3.5	x
CaO	5.2	5.2	6.1	4.0	3.9	3.9	2.9	2.2	5.5	5.4	3.3	nd	n.d	3.0	3.1	3.8
MnO	x	x	x	nd	nd	x	x	x	x	x	3.1	25	25	2.8	3.0	x
Fe₂O₃	x	x	x	x	x	x	nd	nd	nd	nd	4.2	46	46	3.8	4.4	2.1
NiO	nd	nd	nd	nd	nd	nd	nd	nd	nd	nd	nd	17.8	15.8	nd	nd	nd
CoO	x	x	x	x	x	nd	nd	nd	nd	nd	nd	nd	x	nd	nd	nd
CuO	x	x	x	nd	nd	nd	nd	nd	x	nd	3.9	4.1	5.0	3.2	3.7	nd
ZnO	nd	nd	nd	nd	nd	nd	nd	nd	nd	nd	nd	2.9	2.9	nd	nd	nd
As₂O₃	x	x	x	x	x	nd	x	nd	x	x	x	nd	nd	x	1.0	nd
Sb₂O₃	nd	nd	nd	nd	nd	nd	nd	nd	nd	nd	nd	x	nd	nd	nd	nd
PbO	22	23	20	23	23	25	33	39	18	18	45	nd	nd	41	41	8.6