To measure the whiteness of any material, light reflectance instrument is used which is called as LR value. From where I can get this instrument? Please suggest.
Try Hunter Labs. Or sponsor a local graduate or undergraduate to make one for you. If you do this, it may take awhile. This is not as straightforward to do as it may appear.
try a light dependent resistor.
https://eepower.com/resistor-guide/resistor-types/photo-resistor/#
Sridivya Mukkavilli the detector is just part of the issue. The LR value is defined as all light reflected at all angles over the entire visible spectrum. A simple tungsten halogen light and silicon photodarlington detector will cover that range, but will not handle all angles. If you enclose the apparatus in an integrating sphere, you get the angles. However the wavelength distribution will be off. You need to match the wavelength distribution to the response of the human eye. That can also be done, but typically requires calibration of the source, detector, and integrating sphere. All doable, but not as simple as one might think. The simplest method would be to use the above apparatus, but filter the input source with a scanning spectrometer and calibrate on a per wavelength region basis. Cheaper might be to filter the light and detector to match the human eye response (these are available), but these are difficult to calibrate. The method used depends upon how accurately the LV value needs to be determined.
It really depends if the surface is specular (mirror-like), or diffuse (everything else in real life). To measure diffuse surface reflection you would need a device with integrating sphere. Used to be made by Perkin-Elmers. Try to contact Labsphere here: https://www.labsphere.com/labsphere-products-solutions/components-accessories/integrating-sphere-components-accessories/general-purpose-integrating-spheres/?gclid=Cj0KCQjwhb36BRCfARIsAKcXh6G6JLafoUYJK1FzNRtfJgmGhi4SPB5n81C-Y-aAfgkBZ5cT4a0TVQkaAonwEALw_wcB
They have a wealth of information on the subject. They also used to conduct seminars on this type of measurements.
Another interesting devise is offered by K-Space, look here: https://www.k-space.com/products/ksa-emissometer/
Hope this helps.
If your samples are mirror-like, you can use Filmetrics tools, for example:
https://filmetrics.com/thickness-measurement/f20
Otherwise, you need to use an integrating sphere to collect and analyze light scattered by your sample.
Our samples are in the form of powder, potassium cryolite (PAF), we need to measure the whiteness index for the same. The color of the PAF varies from white to grey, it is used for demagging (Magnesium removal) purpose, though its colour does not affect the demagging properties, customer need to knpw the LR value for the same. This powder of PAF, potassium cryolite, can be made into tablet to find out its LR value
Valeriy Sterligov Vadim Boguslavskiy Damien Gray Sridivya Mukkavilli thanks for the technical input, will go through the suggested references
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