In Paul deLima Coffee’s Lab, we explore the world of coffee and help our customers better understand the intricate process behind their morning joe.

The impact on coffee by a host of outside variables is our job to understand. We do the research so you don’t have to, and we share what we know for the curious and spirited coffee lovers out there.


When referring to the ‘strength’ of a cup of coffee, there are two factors to consider: the strength of the coffee flavor and the caffeine content of the coffee. Interestingly, these do not always correlate.

The strength of the flavor often comes from the roast color – the darker the coffee, the stronger its flavor. But, the caffeine content is determined in part by the darkness of the roast as well. More caffeine is burned off in the process of roasting dark coffee than light coffee. So, a dark coffee may taste strong but offer less kick than a light roast.

Factors that impact the strength of flavor include:


Darker roasts have a stronger flavor but less caffeine.


Coffees from different regions impact the palate differently and have different caffeine contents.


The brewing method has a direct relationship with flavor and caffeine content.


Water absorbs solvable solids from the coffee. The higher the coffee to water ratio, the more solids that can be extracted, and the stronger the flavor.


The amount of agitation between coffee and water before filtration can also affect the strength of flavor.


Robusta, as the name suggests, will have more robust flavors and a higher caffeine content than the higher quality, more complex Arabica beans.

7. grind size

Grinding is creating surface area, the finer the grind the more surface area, and the more surface area the more extraction.

8. brew/steep time

The longer the water is in contact with the grinds, the more extraction that occurs. Coffee that is brewed too fast will be weak, but coffee brewed too long will be over-extracted.

9. water temperature

Coffee strength and caffeination are factors of extracting solvable solids from the grinds, and the higher the water temperature, the more extraction.


As the world of coffee moves towards the extreme in terms of quality, the industry has begun to take some new approaches in water chemistry. Solvable solids, the compounds that water extracts from the grounds, form the finished cup of coffee. In order for those solids to bond, they need to bond to minerals; if you were to make coffee with distilled water (water free from mineral content) it would brew like a light tea. It needs minerals to extract.

The question then becomes, what minerals, or in water chemistry speak, what constituents, do what? We know hard water extracts flavors better than soft, we know sulfur is never a pleasant flavor, and we know that chlorine is bad.

Without diving too deeply into technical terms, we can conclude that water should be odor free and color free (we hope that’s obvious), with no chlorine and a Total Dissolved Solids level of around 150 mg/L. Calcium hardness should be around 68 mg/L and Alkalinity of around 40 mg/L. The pH should be around 7 but anything in the 6.5-7.5 will do. Sodium is an interesting character in this play. On first thought, we may assume that sodium is too reactive, but sodium, about 10 mg/L actually contributes some unique characteristics. Magnesium sulfate can also create ideal extraction in the high-specialized pallet.

If you’ve made it this far and are still interested, you may want to be in the coffee business.