WHAT IS DOSE IN ESPRESSO?
Dose is one of the primary variables in an espresso recipe:
A dose can be anywhere from 5 - 30 grams, but currently the favored range in US coffee shops is 18 - 21 g, with a little room on either side for personal preference. Setting the dose determines the rest of your recipe.
Dose = 18 grams dry coffee
Ratio = 1:2
Yield: 36g of espresso
Time: 30 seconds
You could also decide to use a smaller dose with the same ratio:
Dose = 14g dry coffee
Ratio = 1:2
Yield = 28g espresso
Time: 30 seconds
Getting you less coffee but at the same strength/concentration.
HOW DO I DECIDE ON A DOSE?
DOSE TO YOUR BASKET: Think of how much coffee you would like to make. A lot of coffee? Bigger dose. Less coffee? Smaller dose.
That’s really it. Your dose is dictated by the size of basket you choose. If you have a 14g basket, you have a range of 13 - 15g as a dose. If you choose a 21g basket, your range can go up to 22ish grams of coffee.
One thing about baskets- you can have a smaller dose than your basket, it will just end up being kind of messy when you knock out the puck. The space between the coffee bed and shower screen will be so large that excess moisture won’t get pulled out of the coffee bed at the end of your shot, leaving it wet and muddy.
Dosing more than a gram over your basket size will not give the coffee enough headspace as you pull your shot. As the coffee absorbs water and expands, it smushes up* against the shower screen, leading to channeling and over extracted espresso.
*that’s a technical term
DOSE TO YOUR ROAST LEVEL: This has to do with your extraction, or how easily the water dissolves your coffee solids and goes through the coffee bed.
Coffee bean cell structure becomes more porous the longer it's roasted. That increased water solubility means the coffee bed creates lower resistance, and even larger doses of darker roasts (18 - 22g) will extract fairly easily.
Lighter roasts are less porous, because they have been subjected to less heat. That increased density means that the same dose of 18 - 22g of lighter roast coffee will provide higher resistance to the water, making it more difficult to achieve a great extraction. In general, you are better served if you start with a smaller dose (16g) and go from there.
Translation: you can use larger doses with darker roast coffees. Medium and lighter roast coffees are better suited to smaller doses.
Even though people tend to discuss espresso variables one at a time, when you pull a shot, all the factors are working together simultaneously. In your mission to achieve espresso greatness, it can be a lot to think about. Find a dose that seems good for your roast level and gets you the amount of coffee you want (a lot or a little) then stick to it.
Keeping one variable fixed allows you to adjust the other things- ratio, grind size, time, temperature- as you chase after that sweet spot.