There is no perfect weight for a double shot. There are too many variables at play. For example, the weight of your machine changes depending on the beans that you use and so does the weight of your basket (or paper filter). The weather also has an effect on your shot, as it can affect how wet your grinds are.
Essentially, you want to find a puck that’s tight enough packed that it won’t allow liquid to back up into the shower head. You need it to be loose enough so water can flow through at the right rate. It also needs to be distributed evenly and close to your shower screen. There isn’t any one type of puck that will fulfill all your requirements every time.
In short, you’re asking “how long is a piece of string”.
The correct answer for you and your setup is something that you’ll have to determine for yourself. There’s no universal rule when it comes to accuracy in weight measurements. Nevertheless, ratings are nominal values, with a basket rated at 18 pounds containing around 18 pounds worth of fruit (I believe that VST suggests that the permissible error should be +/- 1 pound).
I’ve found that different types of coffee require different amounts. For light roast single-origin coffees, I usually measure 20 grams of beans and make quite short, slower-brewed doubles (35 grams). When I use Italian blends with a classic recipe, I measure 15 grams and create a clear double with approximately 60g of coffee beans (simply double the weight to reach your target weight).
First, you’ll need to find a consistent dosing technique. Experts recommend that beginners use the following steps: Fill the group handle and make sure coffee is distributed evenly. Create a small mound of coffee, then brush off with a straight edge or the side of your index finger to get a fully packed tamper.
Remove excess from the edges by tapping gently on your tamper. Fill and brush again, then tamp to about 15kg or thereabouts for a similar size dose each time. This method may not work for you if your group handle is hard to load; back off just a little bit by adjusting your stirring technique but do so consistently.
Another good method is “dosing in a mountain” and tapping gently to settle any gaps. Ensure everything else has been well-preserved, including level and flat surfaces, then tap gently at 15kg or so like before. Either of these methods should result in a consistent dose each time.
One thing clear is that whatever you do, it MUST be 100% repeatable. This is just one method- but it’s a good one for beginners because it leads to consistency.
If you want the perfect shot of espresso, then here are our tips for success. You’ll want to run your 30ml in 25 seconds pour time (per shot). This is a good starting point, but it’s best if you measure your pour by eye. If the puck looks soaked or too wet, then your dose cannot be right and the espresso might end up tasting bad. On the other hand, if you see holes in your puck, there are channels like these – which usually means that your shot will be disappointing!
Taste the espresso, give it 5 seconds and then determine where you taste it on your tongue. If you taste it at the front of your tongue, the coffee is sour and you need to coarsen your grind; if you taste it at the back of your tongue, the coffee is bitter and you need to fineness your grind.
Never adjust your grind if you’re unsure of what’s making the espresso taste bad.
To keep a coffee from being under or over-extracted, you need to adjust the grind. Imagine a see-saw with sour at one end and bitter at the other. With a Giotto, I try to pour a shot that’s semi-dry on top, slightly ropy in between, and then continuously streaming on the bottom. It usually takes me about 7-9 seconds to pour the shot.