Doram So, for example, a 16-20g IMS basket will be equivalent in size to an 18g VST basket. I may be wrong here, but if I am, can someone explain how the same size basket from VMS will be able to hold a 2-gram range (17-19 for the 18g basket) but the same sized IMS will hold a 4-gram range (16-20)?
They’re not the same size/volume. I bought the IMS competition 16/20g - B702TCH26E to compare with my 18g VST. Only used it for a few shots so can’t really comment yet, although I immediately wanted to switch back to the VST.
The IMS naming convention is explained here:
https://www.imsfiltri.com/wp-content/uploads/2022/06/IMS-Competition-DEFINITIVO.pdf
Essentially, 2T = two cups/double dose, C = convex, H26 = 26mm height, E = hole pattern.
The 18g VST is 24.2mm in height, so the IMS is slightly taller and has a larger capacity. In fact the 20g VST is 26mm high, although the bottom is more flat vs. the convex bottom of the IMS.
IMS do however say that “an approximate weight of ground coffee in grams is associated with each code in the catalogue. The actual capacity of a filter depends on many factors such as the coffee grind or the space that is left between the coffee puck and the showerhead screen.”
So maybe they are being a bit more generous with the range.
If I remember correctly the holes on the IMS don’t go as far to the edge as the VST, and as this particular IMS basket has a more convex bottom it should encourage flow towards the centre of the basket and be more forgiving. That may help with a wider range of doses.
On the other hand a well prepped VST basket may encourage a more even extraction across the puck and a better cup? Who knows.
