Post By trickydicky2
Colorimeter - Measuring roast level
Has anyone tried using a colorimeter to measure roast level? Purpose built lab colorimeters are exxy to buy but I notice there are cheap or free smartphone apps that can output colorimetric values as CIE LAB, chroma, hue, RGB.
Guessing you'd need some sort of white balance calibration and standardised illumination for this to produce results you could use to compare from roast to roast
Has anyone tried this? I'll give it a burl using an app and see if it's useable. Figure it would be worthwhile to measure roast level on both whole bean and ground coffee
Decided a suitable approach will be to use camera flash to illuminate the coffee and use a manually calibrated white balance setting. Ordered a cheap 18% grey card from eBay to use as my white balance standard
This might all come to nothing but I will give it a go and put some results up in a month or so
Originally Posted by trickydicky2
What are you trying to achieve by using one? Assessing the roast depth after the roast has completed? From my quick google, colorimeters are used to measure substances in solution.
Most of us on CS are home roasters using home roasting equipment and judge roast depth by eye or use sound and/or some form of temperature measurement to determine when to finish the roast . I doubt very much whether anyone has tried any form of colorimeter. Would be interested to hear how you get on but it sounds like a lot of bother without much meaningful data unless you are roasting the same bean each time and measure the colour under the same lighting conditions.
From what I can gather a colorimeter is useful for judging the overall roast depth throughout the bean.
You measure the 'darkness' of the outside of the beans, then grind them up and measure the darkness of the beans all ground and evenly disitributed. This may be similar (showing an even roast), or substantially lighter (demonstrating a fast roast where the inside is less developed than the outside – it then gives an average colour that is somewhere in between). This then gives you a measurement the spread of the roast.
While this method has some value, it still needs to be used in conjunction with taste testing - these numbers will never be able to guarantee good flavour, but may help with repeatability and getting new beans into the ballpark of consistent roasting.
But certainly, the fly in the ointment will be repeatable lighting conditions for home use