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Abstract

This experiment tested how different bleach dilutions effectively remove blood from floor tiles and how they might affect the Kastle-Meyer (KM) presumptive blood test. Matte Calacatta 12 in. x 12 in. glazed ceramic tiles were used. Glazed tiles are considered non-porous on the surface but the ceramic body contains pores that can retain blood; this retained blood can be detected by the KM test. The bleach dilutions used to clean the tiles were 0% (water), 25%, 50%, 75%, and 100%. Trial 1 tiles were cleaned during the day while Trials 2-5 were cleaned at night. After the tiles were dried, each tile was divided into 12 zones, swabbed, and tested with the KM kit. A positive result was recorded within 10 seconds. A separate tile was used to determine if bleach alone would oxidize the phenolphthalein and cause a false positive. The bleach alone did not cause a color change but a bubbling reaction did occur. Across all bleach dilutions, the KM still effectively detected blood on most tiles. The results do vary across dilutions and are not linear. Bleach was not a main factor to removing blood and preventing the KM from detecting blood on the Matte Calcacatta glazed ceramic tiles.

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