Wow I'm tired! Tired because I spent until the wee hours of the morning on Skype with Vince from VST. I would have to say it was a most enlightening conversation even at that hour of night! He spent quite some time going over the science of what's going on during an extraction. I have a much better understanding now of why coffee tastes bitter when it's overextracted, or sour when it's underextracted, how the pH changes during the extraction process and how predictably pleasant the taste can be if the percentage of extraction yield and total dissolved solids is right. I.e. if you measure a sample in a refractometer and it's in the right range you know it'll taste sweet. Of course your tastebuds can tell you that 😉 but if the taste is out then the refractometer can tell you what went wrong in the shot, and therefore the precise direction in which you need to go to sort it out. Guesswork adios! This all led into how important a role the filter baskets play in that process. In a previous position the coffee company Vince worked for lost a client whose coffee had suddenly gone sour. The coffee tasted fine on their machine but sour on the client's. They changed water, water filtration, grinder burrs, coffee batch, temperature you name it but the problem persisted so the client walked. Turned out the client had changed their baskets and sure enough when these baskets were tried in a different machine the sourness went with the baskets, and refractometer readings from these baskets came back off the scale no matter what was done with grind, dose, tamp etc! Vince's previous work was in forensic imaging, so it was easy to scan the hole pattern of the basket. It quickly became obvious what the problem was. Apart from varying dramatically in size, some holes were round, some star shaped, some jagged, some completely blocked! This fundamentally affected the way the coffee was extracted which is why it was always tasting sour! This is how the patended scanning process of the basket VST use came about in the first place, and explained why some baskets will yield consistently over or underextracted results, despite the user's efforts (and why people sometimes note an improvement "simply by changing my basket"). I already knew the basket design manufacturing process of the VST unit is critical, and so many factors in the VST baskets (shape, curve angles, material thickness, internal diameter, hole pattern, hole size, hole size consistency etc etc etc) are finely tuned to yield a 'sweet spot' extraction if dosed correctly. But equally important is the imaging system to ensure the baskets are up to spec; if any of those are out the formula doesn't work and the basket won't perform consistently from basket to basket or with different brew parameters. This made me realise that while I or anyone else could (potentially) replicate the design of the VST basket if we could be bothered, without the imaging system to make sure it's all up to scratch there's no way of checking whether the basket will actually perform the way you want it to, both in that basket itself and with any other baskets from the same manufacturer (and that imaging system is patented and used only by VST 😉). It also reinforced what I said in my previous post that, even if someone was able to get the holes under control, if the shape of the basket is fundamentally compromised then extractions ARE going to suffer, if not all the time then certainly when you change brew parameters. Ultimately like always, let your taste buds be the guide, but realise there's serious work and a pile of science behind these beasts rather than just another basket, plus big names who have used them that are backing their performance. I feel more than ever the advice given to Mark Prince, that if they're not working the way you think they should, the problem's more than likely to be on the user side of the portafilter! 😉 Now for some sleep...!
