Some first tests with Sweeney's Transparent Portafilter. Must try some more to 1) prevent seal popping 2) get a nicer extraction, like one normally and easily gets with the L1 and the standard portafilter setup.
Here we used one of the first Londinium machines with the same brew group as is now still used on the Londinium-R: londiniumespresso.com/buy-now/product/191-londinium-r Raising the lever, one creates a low pressure above the puck. If the puck is compacted too tight, it may be lifted for a moment.
Hi Andrew -- it's probably best to find someone nearby you to develop one. A device like this suffers much in use with sealed fittings of very different materials under fast changes of temperatures from room temp to boiling heat and pressure increase and pressure drops between atmospheric and 9 bar, so it's wise anyway to have a technician nearby to monitor and fix the device for the (limited) life span that it has.
