Colour - the history and frustration in the early days

Before I joined the sugar industry - i used to complain about colour testing in oils & fats

Now I have joined the sugar industry - they have my prayer for colour testing :- take a sugar sample, dissolved in water, and take an absorptions reading reading using a spectrophotometer - a common lab instrument.

Why can's oil do the same??

The common method employed us oil is color measuring device called Lovibond tintometer. Take a sample of oil n filled into cell of length 5 1/4" cell for refined and 1" for crude. you view the color through an aperture and compare with some standard color discs in Red, Yellow, Blue

in unit 0.1, 0.2, 0.3......0.9, 1, 2 ,3, 4......9, 10, 20, 30, 40,

red disc is consider the "primary" color or main color
yellow disc is the "secondary" color or supporting color

by using red and yellow disc -- red + yellow, the method call for the naked eyes, even though trained or otherwise, to match the natural orange-color oil with artificial color slide. Of course it will not be 100% matching and subjective to operator error. The repeatability (ie within the same lab) is already high, not to mention inter-laboratory (between 2 different lab). Ever participate in AOCS Smalley cross check and an interlab reproducibility is 0.6Red is reported


As though it is not confusing enough, when palm oil industry first started in the early eighties - they bring in an Tintometer model "D" - this is a multi-purpose tintometer for all product from solid curry powder to liquid oil. This tintometer doest not correspond to the official AOCS Tintometer. Also the users observed a phenomeno - a 2.9Red oil is the same as 3.1 Red Oil - in other word 2.9 Red is darker than 3.0 Red. How come?

the industry normally used Red:yellow in 1:10 ratio, ie 2.9 Red 29 Yellow. To match this oil we used 4 disc - 0.9Red + 2Red + 9 Yellow + 20 Yellow whereas a 3Red 30Yellow oil use 2 disc ie 3 Red + 30 Yellow. The 2- disc less results in a lowering of the color being matched

Later the industry did attempt to bring in the actual aocs tintometer - called model "E" that can rectify problem with a compensating disc. However the industry discover model E give a higher color reading than model D and hence resistance

There was a period where by there is conflicting results due to model D or model E. I have not get in touch with the issue anymore and it seemed by now model D shud be obsolete and problem resolved, i think

Then the USA color come - they asking for Gardner color scale, FAC color etc..... then when Eastern Europe collapse and started to trade, we were horrified when the ex-communists buyer asking for Iodine Color???? what the hell is that

Finally going through some very very old textbook, those day when they don't even have tintometer, the oil chemists then compare color of oil with fixed amount iodine or dichromate dissolved in water. The Eastern block brethren is still using it in the 21st century. Well they are the buyers and we complied by taking our test tube and dissolved iodine with water to check the color of the oil

Of course the capitalist come to assistant again - Lovibond actually developed an Iodine Color Tintometer

having say so much bad thing about the Lovibond Tintometer, it did provide certain standard for the measuring of Refined Oil

However, the distinction stop here. In high color oil like crude palm oil, fatty acid etc the use of Lovibond is limited. Of course we can use a shorter cell to measure the color to give better matching but in the absent of any standard, it rarely used for commercial purpose - one of the problem is fixing the yellow or supporting color. The 1:10 ratio did not work here. Some lab fixed 60 yellow and start to adjust the red color to give the best match

Gardner scale is one used for high color - more for petrochemical industry

Another common scale for PFAD is the FAC color scale (FAC did not standard for Fatty Acid Color, as some trader misintepreted"

FAC color is in odd inter, 1, 3, 5, 7, 9, 11, then for some reason 11A, 11B, 11C and then 13, 15, 17........

CPKO normally around 5 - 9 but fresh PFAD 9 and deterioate very fast to 11C due to iron pick up

The blue color is only used when you have odd color like browish that you need the blue. so far i encounter only twice in my career - one from CPKO milled from burnt crude palm kernel seed, another time is the Crude Rapeseed oil from frost-damaged rapessed. Of course there is one time at our new refinery at china - the water-like refined rapeseed oil was match with Red, Yellow and Blue and nobody anything. Yours truly arrived and found the Tintometer is being assembled wrongly - not by the local but the expat "chemist" - can anyone guess who he is??