Back to Brass
ML00156 - Jan.2020donated by: Ícaro José de Araújo Silva

Antique Silver Plated Decorative Piece

Image presenting the back of the coaster where the microstructure of the substrate was identified. The composition of the brass (about 35% Zn) indicates that the expected structure is alpha plus beta. The front of the coaster presents two grooves which surface morphology was analyzed by scanning electron microscopy.

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Image presenting the back of the coaster where the of the substrate was identified. The composition of the brass (about 35% Zn) indicates that the expected is plus beta. The front of the coaster presents two grooves which surface morphology was analyzed by .
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Material

Brass
  • UNS C85710
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Description

In 2019, a set of 6 metallic coasters was acquired in an antique store in Porto (Portugal) and the physical characteristics (color and weight) associated to the handmade look, drew attention and aroused interest in finding out how it was manufactured. One piece was carefully analyzed by nondestructive metallurgical tests (surface analysis) that indicated that the decorative parts were manufactured in a cast Yellow Brass Alloy, Silver Plated finished. This composition became obsolete in 1992.

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Chemistry (% in weight)

Product

60.9Cu; 35.4Zn; 0.2Fe; 0.1Ni; 2.3Pb; 0.16Sn; 0.82Al.

Associated Images
The coasters present a handmake look. The grooves are of different sizes and the octogonal shape is irregular. The pieces presented a weight that suggested that the bright finish is a metallic coating, later identified by EDS analysis as silver coating, typical of a decorative plating.
452
VIEW
ML00156 / Jan.2020
Antique Silver Plated Decorative Piece
M - BrassP - Decorative PieceAp - OrnamentalCd - Non Destructive Examination
Cm - Aspect Before AnalysisDf - General View
Piece that was analysed by non destructive tests. Octogonal shape. Two irregular grooves. The coaster was manufactured in a cooper alloy substrate and a metallic coating. The analysis to reveal the substrate microstructure was conducted on the back of the part, in a non destructive preparation, that included light grinding, polishing and etching.
61
VIEW
ML00156 / Jan.2020
Antique Silver Plated Decorative Piece
M - BrassP - Decorative PieceAp - OrnamentalCd - Non Destructive Examination
Cm - Aspect Before AnalysisDf - General View
Light grinding the back of the coaster. The surface was only partially ground, removing the metallic coating, and exposing the substrate, that appeared yellow indicating the manufacturing in a cooper alloy.
63
VIEW
ML00156 / Jan.2020
Antique Silver Plated Decorative Piece
M - BrassP - Decorative PieceAp - OrnamentalCd - Non Destructive Examination
Cm - Preparation TechniqueDf - General View
Aspect of the back of the coaster after grinding. The coating was partially removed. The chemical analysis was conducted in the ground part to obtain the composition of the substrate, that showed to be a yellow brass alloy. It is interesting to note that the alloy presented 2.3% lead.
63
VIEW
ML00156 / Jan.2020
Antique Silver Plated Decorative Piece
M - BrassP - Decorative PieceAp - OrnamentalCd - Non Destructive Examination
Cm - Preparation TechniqueDf - At the Surface
Back of the coaster showing the region that was prepared for the non destructive analysis. It was ground and polished (the coating was removed), showing the yellow aspect of the substrate, in the left bottom part of the image.
64
VIEW
ML00156 / Jan.2020
Antique Silver Plated Decorative Piece
M - BrassP - Decorative PieceAp - OrnamentalCd - Non Destructive Examination
Cm - As polishedDf - General View
Image presenting the back of the coaster where the microstructure of the substrate was identified. The composition of the brass (about 35% Zn) indicates that the expected structure is alpha plus beta. The front of the coaster presents two grooves which surface morphology was analyzed by scanning electron microscopy.
65
VIEW
ML00156 / Jan.2020
Antique Silver Plated Decorative Piece
M - BrassP - Decorative PieceAp - OrnamentalCd - Non Destructive Examination
Cm - Surface AspectDf - General View
Aspect of the coaster surface grooves, by scanning electron microscopy in a low magnification, showing in the right side the flat region that serves as a support; and in the left side the decorative grooves. The smooth surface in the groove suggests that the coasters were manufactured by casting.
66
VIEW
ML00156 / Jan.2020
Antique Silver Plated Decorative Piece
M - BrassP - Decorative PieceAp - OrnamentalCd - Non Destructive Examination
Cm - Surface Aspect by SEMDf - At the Surface
Detail of the previous photo showing the flat surface in the right side and the grooves in the left side. The flat side is scratched and the grooves presented a smooth finishing (with dendritic morphology).
57
VIEW
ML00156 / Jan.2020
Antique Silver Plated Decorative Piece
M - BrassP - Decorative PieceAp - OrnamentalCd - Non Destructive Examination
Cm - Surface Aspect by SEMDf - At the Surface
Detail of the flat scratched region of the coaster surface. The dark grey "nodules" are lead (Pb) base inclusions.
50
VIEW
ML00156 / Jan.2020
Antique Silver Plated Decorative Piece
M - BrassP - Decorative PieceAp - OrnamentalCd - Non Destructive Examination
Cm - Surface Aspect by SEMDf - At the Surface
Detail of the groove region, showing a typical casting morphology at the surface: smooth and presenting a dendritic aspect with interdendritic shrinkage. Some dark grey "nodules" with Pb inclusions are also observed.
51
VIEW
ML00156 / Jan.2020
Antique Silver Plated Decorative Piece
M - BrassP - Decorative PieceAp - OrnamentalCd - Non Destructive Examination
Cm - Surface Aspect by SEMDf - At the Surface
There are some regions in the coaster surface where pores associated to shrinkage is evident.
49
VIEW
ML00156 / Jan.2020
Antique Silver Plated Decorative Piece
M - BrassP - Decorative PieceAp - OrnamentalCd - Non Destructive Examination
Cm - Surface Aspect by SEMDf - Casting defects
Metallographic aspect of the polished surface of the (back of the) coaster, showing pores and shrinkages, typical of a casting structure.
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VIEW
ML00156 / Jan.2020
Antique Silver Plated Decorative Piece
M - BrassP - Decorative PieceAp - OrnamentalCd - Non Destructive Examination
Cm - As polished micrographyDf - Casting Structure
Same region of the previous image but is a higher magnification, showing the metallographic aspect of the polished surface of the (back of the) coaster. Shrinkage with a dendritic morphology typical of a casting structure.
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VIEW
ML00156 / Jan.2020
Antique Silver Plated Decorative Piece
M - BrassP - Decorative PieceAp - OrnamentalCd - Non Destructive Examination
Cm - As polished micrographyDf - Voids
Low magnification metallography of the coaster after etching, revealing a casting structure of alpha plus beta phases. Beta is the dark brown matrix phase and alpha is the dendritic yellow phase.
45
VIEW
ML00156 / Jan.2020
Antique Silver Plated Decorative Piece
M - BrassP - Decorative PieceAp - OrnamentalCd - Non Destructive Examination
Cm - NH4OH+H2O+H2O2 Etched MicroDf - Alpha and Beta
Metallography of the coaster after etching, revealing a casting structure of alpha plus beta phases. Beta is the dark brown matrix phase and alpha is the dendritic yellow phase.
48
VIEW
ML00156 / Jan.2020
Antique Silver Plated Decorative Piece
M - BrassP - Decorative PieceAp - OrnamentalCd - Non Destructive Examination
Cm - NH4OH+H2O+H2O2 Etched MicroDf - Alpha and Beta
High magnification metallography of the coaster after etching, revealing a casting structure of alpha plus beta phases. Beta is the dark brown matrix phase and alpha is the dendritic yellow phase. The non destructive preparation created a metallographic surface not well polished (full of grinding scratches).
48
VIEW
ML00156 / Jan.2020
Antique Silver Plated Decorative Piece
M - BrassP - Decorative PieceAp - OrnamentalCd - Non Destructive Examination
Cm - NH4OH+H2O+H2O2 Etched MicroDf - Alpha and Beta