The VST app factory presets assume your coffee will have a 1% carbon dioxide content — i.e., you think you have 1kg of coffee from your supplier but you really only have 990g. To measure the real amount in any given coffee, take a certain portion, let’s say 100g and grind it very fine on a hand grinder. Make sure you grind every bean fragment! Hand grinders have almost zero grind retention which makes them ideal for this experiment.
A page from the settings menu of the Coffee Tools app
Leave your coffee grinds on a flat surface which will allow them to degas. 50% of the roasting gas is expected to escape in 5 minutes, so if you leave the grinds for 60 minutes, you should have a usable estimation. You can leave the grinds longer but this creates complications. For instance, the atmosphere surrounding your grinds might be high in moisture, causing your beans to absorb water and hence increasing their weight. This is a time-consuming procedure to repeat for every coffee on offer in a cafe or roastery, so you can use our recommended presets which make some assumptions about good roast development and colour but will help you arrive at the right numbers.
Here we devise an experiment with a very precise scale to estimate CO2 content
CO2 Loss Experiment Summary
The coffee we used for this was the Guatemalan Finca Insul from Onyx Coffee Lab in Northwest Arkansas which was a light filter roast. Please note this coffee had travelled to us by air freight and was two weeks from roast. The results of this video are not intended to be a guide for your settings. Our intention is simply to show you that there is a noticeable change in mass as a result of grinding coffee. A fresher, dark roasted coffee is expected to have a much more significant change in mass.