COLOR – COLOUR – ASTM D1500 – ASTM D 1500 COLOUR SCALE
Color of an oil can be used as indicator of the health of the oil. The color of an oil can range from colorless, transparent, pale yellow, yellow, bright yellow, amber, brown, dark brown, hazy, turbid, opaque, milky, black, etc.
A change in color usually indicates either a change in the chemistry of the oil or contamination of the oil.
There are a number of possibilities for the change in color of the oil, some of which are highlighted as under :
- Oxidation of the oil
- Mixing of one grade of oil with other
- Oil darkening due to petrochemical reaction
- Ageing of the oil
- Water ingress in the oil
- Soot formation, insolubles, dirt and solid contaminants
- Varnish – or varnish potential – which is a thin insoluble contaminant formed due to depleted additives or by products of oil degradation
The colour of the oil is usually and widely used is the ASTM Colour Scale or “mineral oil colour value” for testing, analysis and grading of oils, lubricating oils, petroleums, diesel fuels and heating oils. The colour scale is from 0 which is water white to 8.0 units which is very dark or almost black. The testing is done in 0.5 increment units.
Representation of the ASTM D1500 Colour Scale is given below :
The instrument used in our laboratory for measuring the ASTM D1500 Colour Scale is: