CoyoteOldMan
Questions are from me. Responses are from Clare who work closely with Brandon at Deva:
- People I know who have had a chance to use it tell me it retains most of the grind while grinding and starts dumping it all out after you turn it off. I’ve seen this in videos as well. That you basically just have to press the power button a few times to get all the grinds out but after that it has very little retention. Is that how it’s supposed to work? Or are you working on modifying it so you don’t have to press the power button several times to get all the grinds out?
Due to the build up of static, grounds may remain in the funnel while grinding. This static can be caused by grinding at a higher RPM, and not using the RDT method. We supply an RDT with each KOPI Deva and recommend 2-3 sprays per 18g to help reduce the static build up within the funnel. As we don’t have bellows in our grinder, we recommend pressing the power button a few times to get the remainder of the grounds out, and letting gravity do its thing by assisting with the grounds to fall into the dosing cup.
2. Do grinds start caking and getting trapped on the inner funnel and/or the wipers attached to the burrs and then lead to some grounds exchange happening every time? If so, have you measured the average amount of exchange for the machine?
After rigorous testing, the retention of our grinder is within 0-0.2g of remaining coffee grounds. This is in line with a low retention grinder and it can be further assisted by using the RDT method and pulsing the side button a few times to help let the remaining grounds fall out of the funnel. There may be some grounds left on the walls of the funnel and the wipers, but it’s minimal and again, within the 0-0.2g of coffee grounds that may remain in the grinder.
3. On the website you talk about a patent pending design which creates a small pressure differential. I asked some people who know physics more than I do and here’s what they told me: "It looks to be impossible for a pressure differential to be created given what we know about the design of Deva. The funnel at the top and the chute at the bottom are open, at atmospheric - thus equal - pressure. As far as I can tell, there is no ‘pressure-retaining’ mechanism or device inside the grind path, just the axle and its supports, and the burrs. This means that - including the “fluid” that is the coffee-and-air mix in its various states of grind - all of the grind path is at the same pressure when the motor is not running. When the motor runs, there will be some ‘pressure’ (air speed) generated by the burrs (they can look a bit like turbine vanes, if you think about it), centrifugal forces that push the coffee/air mix, and some viscous drag around the axle - not different from any other flat-burr grinder."Without giving away any of your secret sauce given that the design is patent-pending and not fully patented, would you nevertheless be able to enlighten us on how a pressure differential is created?
As the lower burr spins, and the wipers spin with it, it creates a pressure difference between the grinding chamber and the funnel. Another way of wording this is; when the lower burr spins, there is a pressure difference between the area above the lower burr, and the area below the lower burr.
Where this differs from other grinders;
In grinders where coffee grounds exit horizontally from the burrs, this difference in pressure is only realised at that exit chute, which is usually a circular or rectangular hole.
In the KOPI Deva, the pressure difference acts uniformly around the lower burr, which is also the exit chute, which helps to lower retention and prevent coffee grounds from being stuck to surfaces within the grinding chamber, or in the funnel.
There are no pumps, or anything secret in the patent pending design which creates this pressure difference. It’s true that it is a phenomenon created by a spinning burr, but in the case of the KOPI Deva, the phenomenon is utilised to help minimise retention.
