This video explains how to use the app. For those of you who prefer to read an explanation, we provide the written instructions below.
Prepare Your Grinds
The easiest way to get good results is to use a backlight — this maximises the contrast between the grinds and the background. To do this, you can simply use an iPad, or a laptop screen placed horizontally. Load up this webpage and display it full screen: this provides a white background and a scale that you can use to calibrate the size of the image.
Next, spread the grinds onto the background in such a way that as many particles as possible are in the image but none of them are touching each other. The easiest way to do this seems to be to sprinkle the grinds using finger and thumb. Any particles that are touching after this can be moved apart with the tip of a chopstick, or bigger clumps can be picked up and sprinkled again. Whatever method is used, it’s important that all particles you pick up are returned onto the background, to avoid preferentially removing particles of a particular size.
Take a Picture
‘With coffee grind analysis, as with everything else, it’s garbage in, garbage out’, Professor Abbott points out. Getting a good picture in the first place will make finding the correct settings for later analysis considerably easier. For best results, use a camera with any automation settings (for example, white balance and auto focus) turned off.
Position the camera as perpendicular to the image as possible, ideally using a tripod with a spirit level to hold it steady and square. Focus the image carefully, and use the highest resolution available to you.
Then measure the full length of the ‘scale’