Hi,
I've been brewing with my rancilio silvia for a number of years now and am using a bottomless portafilter. Whenever I brew, the shot doesn't come together into a nice cone and there will be certain part of the bottom of the filter basket which coffee does not come out from and instead, there will be a cone or two from the left and right side of the basket. In essence, the problem is there are "dead spots" in my extraction. I have managed to get nice tiger striping extractions only occasionally. I feel that my tamp is level enough and i am using a VST basket as well so its definitely not the basket issue.
1)Do you guys know what is the problem? Am i grinding too fine or is the dose too high that's why?
2) Does the roast level of the beans play a part? When I see the extraction, due to the lighter roast of beans that I am using (beans from homeground, apartment), it is not as syrupy and is "thinner" and could that be the reason for not a so aesthetic looking extraction? Will darker roasted beans be easier to get the tiger striping extraction?
TIA for advice!
bottomless filter is a good learning tool but try not to overanalyse. Its only one of the tools that you can use to assess for even distribution. Taste is the ultimate indicator of good extraction. You already suspected some of the reasons for the less then perfect looking espresso pulls.
A few reasons why you are not getting a good pattern on your bottomless. not all of them are related to your technique or getting a good extraction!:
1. Using light roasted beans - Try using a medium to darker roast. I recommend using Ona Coffee Hitman, highlander coffee for consistent results. these are easy to brew with. Yes home ground does go for lighter roast style. lighter roasts are harder to extract properly
2. Using old beans - 7-21 days post roast date is ok.
3. Using water that is too cold - When using the silvia you have to time when to pull the shot.
4. using vst - Yes using a VST basket may result in inconsistent results because of the high surface area of the basket that is perforated and makes it much easier for liquid/dissolved/undissolved solids to pass thru. If you get it right VST baskets allows you to get good results for light roast coffee because you have to grind finer.
5. Disturbed puck due to too high coffee bed - Adjust your dose so that your shower screen does not touch your puck and disturb its integrity when you lock in your portafilter.
6. Disturbed puck due to no preinfusion - this is less of a problem but still a potential one. Your puck may have been disturbed with the shock of sudden pressure hitting the puck disturbing its integrity.
5. and Finally - uneven distribution - use WDT. I use it all the time for consistent results.
