Why are some coffees roasted darker and others lighter? Is there actually a science to the differences? Why do some shops offer different sizes for drinks while others say there's only one size?
The best answer I can give you to cover all those questions is...."Sure?"
The truth is, some baristas might say one thing, while others say the complete opposite. The coffee industry is generally ambiguous with just about everything. Every now and then we seem to come to a conclusion, but even then, there's always a few outliers saying something to contradict.
What I can do is give you my opinion from my trials and errors.
Why are some coffees roasted darker or lighter?
-I roast darker and lighter based on what I intend to use the coffee for. Generally, I categorize coffees into two groups: Espresso or Filter. I will generally roast espresso a bit longer (presumably darker) and coffees for filter drip quicker (lighter). The reason that the length of time is associated with darker roasts is that the temperature should be increasing with time. The higher the temperature over time, the darker the roast. The darker the coffee, the more soluble it is. When making espresso, you have a very short window of time to make something taste great (~30 seconds) with a very small amount of coffee to water. Needless to say, there isn't a lot of room for error. So, the darker the roast, the easier it can be to make that espresso taste great.
Is there a science to the differences in the roasts?
-Sure. I use roasting software to help guide my roasts. It helps me visually see what's going on with the temperature of the coffee over time. I can make adjustments based on data and not rely just on my senses of smell and sight (which is still helpful). It also allows me to be much more consistent by adding more variables to my roasts rather than just using a stopwatch. Coffee will react differently to different levels of heat and airflow, which ultimately changes how coffee tastes. Think of a well-done steak versus a medium-rare one.
Cup sizes, what's the deal?
-Some shops will give you an option. 12oz, 16oz, 24oz??!!
I look at it like this, when shops give you an option, it's like they're telling you to choose your own adventure. It might taste great or it might leave you with wanting more. It's up to you. My perspective from the barista side is that we create beverages that have a specific amount of coffee and milk, based on what I feel brings out the most and best out of that combination. Darker roasted coffee can have more bitter and smokey flavors to it, so combining it with more milk can help balance those flavors (milks contain sugar and that sweetness increases with heat). A specific amount of coffee to milk will create a certain flavor (hopefully balanced and memorable). Our job is to figure out how to make a beverage taste great. That goal might require us to make sure a beverage, let's say a cappuccino, to be in a certain size cup because that amount of coffee and milk makes what we consider a cappuccino to taste great.
I like to think I have a wide spectrum of roasting, from dark to light. I even have what we call an "Omni-Roast" which is intended for both espresso and filter purposes. So when you can't decide on what to buy, you really can't go wrong with the El Soldador coffee under our SHARE collection