MÖSSBAUER STUDIES ON THE NATURE OF THE RED OR BLACK GLAZES ON GREEK AND INDIAN PAINTED WARE

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MÖSSBAUER STUDIES ON THE NATURE OF THE RED OR BLACK GLAZES ON GREEK AND INDIAN

PAINTED WARE

G. Longworth, M. Tite

To cite this version:

G. Longworth, M. Tite. MÖSSBAUER STUDIES ON THE NATURE OF THE RED OR BLACK

GLAZES ON GREEK AND INDIAN PAINTED WARE. Journal de Physique Colloques, 1979, 40

(C2), pp.C2-460-C2-461. �10.1051/jphyscol:19792160�. �jpa-00218535�

JOURNAL DE PHYSIQUE

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MOSSBAUER STUDIES ON THE NATURE OF THE RED OR BLACK GLAZES 3 N GREEK AND I N D I A N PAINTED WARE

G . Longworth and M.S. ~ i t e '

NucZear Physics Division

(81,

Atomic Energy Research EstabZishment, HameZZ, Oxfordshire

*Research Laboratory, The B r i t i s h Museum, London

RBsum6.- La s p e c t r o s c o p i e Mzssbauer e t l a microscopic e l e c t r o n i q u e b balayage (SEM) o n t e t 6 u t i l i s e e s pour e t u d i e r d i v e r s d c h a n t i l l o n s p r o t 6 g 6 s p a r un revstement. En u t i l i s a n t l a d i f f u s i o n d e s rayons X

(Mzssbauer), on a montre que 1 a . p a r t i . e b r i l l a n t e rouge e t n o i r e d e s Q c h a n t i l l o n s de l a GrCce A t t i q u e c o n t e n a i e n t respectivement de l a m a g n e t i t e e t de l ' h a e m a t i t e , t a n d i s que l e coeur ne c o n t i e n t que l ' h a e m a t i t e . Les mesures par SEM montrent que l a p a r t i e b r i l l a n t e a une d p a i s s e u r de 30 pm e t e s t totalement v i t r i f i 6 e . Pour l e s o b j e t s 'Samien' on a r e l e v d l a presence d ' h a e m a t i t e B l a f o i s dans l a p a r t i e b r i l l a n t e rouge e t dans Le coeur de l ' e c h a n t i l l o n . L 7 6 p a i s s e u r du v e r n i n o i r d e s o b j e t s p o l i s du Nord de 1 ' I n d e ' (NBPW) e s t e n v i r o n 10 pm mais n i l e v e r n i n i l e coeur ne s o n t v i t r i f i s s , ce q u i i n d i q u e une p l u s f a i b l e temperature de cuisson. Le s p e c t r e de d i f f u s i o n d ' b l e c t r o n s e f f e c t u e s u r l e v e r n i (NBPW) f a i t apparaTtre un d o u b l e t d'une s t r u c t u r e f e r r i q u e b i e n que l ' u n des b c h a n t i l l o n s dome un s p e c t r e contenant une composante magngtite, l e coeur c o n t i e n t du f e r dans une s t r u c t u r e de s i l i - c a t e . Les r e s u l t a t s s o n t d i s c u t e s dans l e but de comprendre l e s techniques de f a b r i c a t i o n u t i l i s 6 e s . A b s t r a c t . - Mgssbauer spectroscopy and scanning e l e c t r o n microscopy (SEX) has been used t o s t u d y sam- p l e s of v a r i o u s t y p e s of p a i n t e d ware. Using Mzssbauer X r a y s c a t t e r i n g , t h e b l a c k and r e d g l o s s on samples of Greek A t t i c ware a r e shown t o c o n t a i n r e s p e c t i v e l y magnetite and h a e m a t i t e , w h i l e the core c o n t a i n s h a e m a t i t e . SEM a n a l y s i s shows t h a t t h e g l o s s h a s a t h i c k n e s s of

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30pms and i s t o t a l l y v i - t r i f i e d . Both t h e r e d g l o s s and core of Samian ware c o n t a i n haematite. The g l o s s t h i c k n e s s on I n d i a n Northern Black p o l i s h e d ware i s found t o be

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10 pms w h i l e b o t h t h e g l o s s and c o r e e x h i b i t no v i t r i - f i c a t i o n i n d i c a t i n g a lower f i r i n g temperature. Mzssbauer e l e c t r o n s c a t t e r i n g s p e c t r a f o r t h e g l o s s c o n s i s t of a f e r r i c doublet although one sample g i v e s a spectrum c o n t a i n i n g a magnetite component, w h i l e t h e core c o n t a i n s i r o n i n a s i l i c a t e s t r u c t u r e . These r e s u l t s a r e d i s c u s s e d i n terms of t h e

suggested techniques f o r manufacture.

Recently G s s b a u e r measurements have been made on potsherds and on c l a y types from several d i f f e r e n t

c u l t u r e s / l / . A sample of Greek A t t i c b l a c k g l o s s has been shown t o c o n t a i n m a g n e t i t e , by t h e use of Mzssbauer X r a y s c a t t e r i n g (Cm) and a b s o r p t i o n

techniques 121. This work h a s been extended h e r e t o cover f u r t h e r examples of t h i s type (2 samples), Greek A t t i c r e d g l o s s ( 2 ) , Samian ware (2) and of I n d i a n Northern Black P o l i s h e d ware (NBPW)(4). Both CXM s c a t t e r i n g and conversion e l e c t r o n (CEM) s c a t - t e r i n g a r e used t o examine t h e g l o s s non-destructi- v e l y , t o d e p t h s of r e s p e c t i v e l y

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50 pms and 0.2pms and t h e measurements a r e combined w i t h an examina- t i o n of tKe p o t t e r y u s i n g scanning e l e c t r o n micros- copy (SEM) 131.

The CXM s p e c t r a f o r t h e Greek A t t i c Black g l o s s c o n t a i n magnetic components w i t h f i e l d s H

2

489,465 kOe ( f i g . ] ) which may b e a s s o c i a t e d w i t h an impure form of m a g n e t i t e . The corresponding s p e c t r a f o r t h e Greek A t t i c r e d g l o s s c o n t a i n a magnetic component from h a e m a t i t e (H

2

505 kOe) which i s a l s o p r e s e n t i n t h e a b s o r p t i o n s p e c t r a f o r t h e r e d c o r e m a t e r i a l of each type. The s i m i l a r magnetic f r a c - t i o n s i n c o r e and g l o s s suggest t h a t t h e r e a r e no

l a r g e d i f f e r e n c e s i n oxide p a r t i c l e s i z e . SEM exami- n a t i o n of t h e Greek A t t i c black ware shows e x t e n s i v e v i t r i f i c a t i o n of t h e body f a b r i c ( c o r e ) w i t h a sug- g e s t e d f i r i n g temperature i n t h e range 8 5 0 - 1 0 5 0 ~ ~ . The b l a c k g l o s s e x h i b i t e d t o t a l v i t r i f i c a t i o n w h i l e t h e r e d g l o s s although more compacted t h a n t h e body, was n o t f u l l y v i t r i f i e d . The t h i c k n e s s o f t h e b l a c k g l o s s was found t o be 20-30 'm f o r which range about 50-60% of theCXM spectrum w i l l be c h a r a c t e r i s t i c of t h e g l o s s .

As expected t h e s p e c t r a f o r r e d Samian Ware, b o t h f o r t h e g l o s s (CXM) and c o r e (absorption)showed

a n a p p r e c i a b l e magnetic component due t o h a e m a t i t e (H g 507 kOe) ( f i g . l ) . SEM measurements a g a i n showed t h a t t h e r e d g l o s s was f u l l y v i t r i f i e d .

CXM s p e c t r a f o r t h e g l o s s on I n d i a Northern Black P o l i s h e d ware (NBPW) c o n t a i n e d two d o u b l e t s with s p l i t t i n g s A 2.4 mm.s-': ~ e and 0.9 m.s-l: ~ '

~ e and no magnetic components. Absorption s p e c t r a ~ + f o r the g r e y c o r e m a t e r i a l showed e s s e n t i a l l y s i m i l a r d o u b l e t s b u t w i t h a s l i g h t l y lower f e r r i c f r a c t i o n .

SEM d a t a i n d i c a t e d t h a t t h e g l o s s t h i c k n e s s was o n l y 10-15 Ums however s o t h a t only 20-30 % of

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19792160

the CXM spectral area is due to material in the gloss. CEM spectra were therefore taken and found to consist essentially of a ferric doublet. For one sample however there was a magnetic component (~50%

total area) with H 490 kOe, (fig. 1) probably due to magnetite. The core of NBPW shows essentially no vitrification which suggests a firing temperature below 80O0C. The gloss layer although more compacted than the core is definitely not vitrified, and is oxidised to a red colour when refired in air to 900°C.

Fig. 1 : ~Essbauer conversion X ray (Cm) scattering spectra for Greek Attic black gloss (A) and Samian ware (B) and M6ssbauer conversion electron (CEM) spectrum for Indian Northern Black Polished ware (C).

The solid lines represent least squares fits to the data and the zero of the velocity scale refers to the shift of cl-iron.

The colour of the gloss in Greek Attic ware is thought to have been determined by control of the

the assignment of the iron oxides, i.e. core and red gloss (haematite) and black gloss (magnetite).

The black gloss of NBPW is thought to have been produced by firing in a reducing atmosphere of a slip made up of red ochre, clay and alkali /5/. Pre- liminary XRF measurements do indicate a higher iron fraction for the gloss than the core. It is possible that the less pronounced magnetite fraction obser- ved could be due to the lower firing temperatures involved although the sensitivity of the CEM techni- que is limited for these samples. The grey core ma- terial is probably associated with iron in a silica- te structure.

These measurements demonstrate the usefulness of a combination of Mzssbauer and SEM measurements particularly for the Indian pottery where the gloss is too thin to be examined meaningfully with CXM scattering. Here CEM scattering may be used although the spectral areas are appreciably smaller than for the corresponding CXM spectra and also there is pre- sumably a contribution to the spectrum from a weathe- red layer at the surface of the gloss.

References

/l/ Gangas, N.H.J., Sigalas, I. and Moukarika, A., J. Physique

37

(1976) C6-867.

/ 2 / Longworth, G. and Warren, S.E., Nature,

255

(1975) 625.

/3/ Tite, M.S. and Maniatis, Y., Nature,

257

(1975) 123.

/4/ Bimson, M. The Antiquaries Journal,

2

⁽¹⁹⁵⁶⁾

200.

/5/ Hegde, K.T.M., Antiquity,

E

(1975) 187.

kiln atmosphere during firing using essentially one clay type for core and gloss albeit in a more divi- ded form for the gloss 141. This is consistent with