b . Preliminary testing
Preliminary testing was done to ensure that variables such as spraying techniques were consistent . 24 samples of swatches , measuring 10cm by 10cm were gathered from one 100 % cotton denim dress , one 100 % top and one 100 % polyester jacket procured from charity shops . Of these 24 swatches , 12 were cotton and the remaining 12 were polyester . 6 samples of each material acted as controls and the remaining 6 samples had 0.3mL of ovine blood added to the middle . Using the available washing machines in the University Laundrette , the cotton samples were washed at 60 degrees and the polyester samples at 40 degrees as per the recommended settings from the clothing manufacturers . The samples were left to air dry with the temperature controlled to 21 degrees .
The luminol was made up using the Weber Method ( Weber , 1966 , pp . 410 – 423 ). 3 different 500mL of stock solutions of luminol was made . These solutions contain hydrogen peroxide and sodium hydroxide and were further diluted with distilled water to make up a final volume of 500mL . The procedures for these solutions can be found below :
1 . 0.354g of 3-aminophthalhydrazide will be combined with 62.5mL of 0.4 mol dm3 sodium hydroxide . A final volume of 500mL will be made up with distilled water
2 . 8 g of sodium hydroxide will be added to 500mL of distilled water
3 . 10ml of 30 % H2O2 will be mixed with 490ml of distilled water
c . Materials and methods
The experimental method was split into 4 test batches : the preliminary testing and 3 experimental conditions . In each testing condition , there were two controls and two testing conditions . A total number of 32 swatches were used in each testing section apart from in the preliminary condition where 24 swatches were used thus bringing the total number of swatches to 120 . In each condition there were 16 polyester swatches and 16 cotton swatches . Blood was added to 8 cotton and polyester swatches , in a fume cupboard , and the remaining 8 swatches acted as controls . The swatches were then left to dry for 2 weeks .
Net washing bags were used to avoid the loss of the swatches in the machine drum . 12 swatches were split into 8 different laundry bags and after the first wash , 4 were taken out of each bag . After the second wash , 4 further swatches were taken out and the remaining 4 were the final wash . This was to adhere to the experimental conditions where the swatches in experiment 1 were washed once , twice for experiment 2 and thrice for experiment 3 . This was the same for both the controls and the stained swatches . The controls and the swatches were not washed together so that no contamination of blood should occur . The clothes were then hung dry on an airer for 24 hours at a temperature 21 degrees . The washed samples were then stored in sandwich bags and photographed a week later .
d . Results
The software programme COREL Photo Paint was used to provide exposure histograms for the swatches . Using the histograms and the blue channel , pixels from the 250 to 255 range were used . This is because most of the pixels appeared on the righthand side of the histogram . The blue channel , along with the green and RGB ( red , green , and blue ) are three colour histograms known as the channel histograms . Each type illustrates the distribution of pixels in this channel ( Pixel Magazine , 2017 ). The blue channel was used as it corresponds to the blue colour emitted due to the luminol reaction and as such was used to view the brightness level of the blue colour in the images . The idea of the percentage change was to show how much light has been received in the 250 to 255 range . The images were not cropped as it was hard to see the control samples where no visible outline was present
Figure 5 shows a cotton swatch , on the left , that has been washed once with a biological laundry tablet . Some blood can still be visualised in the centre of the swatch . The image on the right is of the same swatch but after luminol addition . The histogram
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