Kenneth Pye Associates Ltd.
 Scientific Research, Consultancy and Investigations

              
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Stone floor tile discolouration
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In a study investigating the cause of discolouration in oolitic limestone floor tiles, stone samples were analysed using optical microscopy, scanning electron microscopy, x-ray chemical microanalysis and colour spectrophotometry.  Results showed that discoloured areas occurred where the stone was of low quality, where impurities (iron, silicon, aluminium, potassium and magnesium) accumulated along surfaces of pores and narrow fissures.  Discolouration was caused mainly by oxidation of the ferrous iron in the tiles after they were laid and while they dried out.

       
Optical micrograph of specimen floor tile showing                    Optical micrograph of a thin section of limestone
brown discolouration (x 20 magnification)                                (x 20 magnification)

       
Scanning electron micrograph of thin section                            Scanning electron micrograph of specimen floor tile
(x 80 magnification)                                                                (x 250 magnification)

       
X-ray micrograph of discoloured section of                Colour comparison of good quality limestone tile (top curve)
floor tile, showing the presence of impurities               and low quality, discoloured limestone tile (bottom curves)
(Fe, Mg, Al, Si and Fe)                                             using quantitative spectrophotmetry

Kenneth Pye Associates Ltd. - Environmental Consultants
Page last modified: July 11, 2007