When is coffee extracted? What is over extraction?


Hi everyone!

Today I am going to conduct a pretty simple experiment. I am going to brew a 150g drip coffee, and capture the first, middle and last 50g separately. I will be checking how the extraction changes during the course of the brewing process, how each part tastes, and check if any of them will start to have a bad over-extracted taste.

It is an interesting little experiment, but I might get some insight into what the best brew ratio is based on the results.

Let’s get right in to it!

The Method

The method is very simple.

Prepare any dripper you like, and a few cups. I will be using the HARIO SWITCH as a normal V60 dripper by keeping the switch open. (Just a side note, the HARIO SWITCH is such a versatile brewer. Do look into it a bit if you have not heard of it before). As for the cups, I prepared 3 identical cups (+1 extra) for my setup. The cups don’t really need to be the same ones.

Next grind your beans as you would normally. I used the ROKUMEI BLEND from ROKUMEI COFFEE for the experiment. (Here’s a review of it, but sorry its only in Japanese) For the ratio, I used 9g of beans for the 150g of water. This is my usual ratio, if you have a different ratio, by all means use whatever ratio you like.

Since I prepared 3 cups, I will divide the water in by 3 portions of 50g each. I will pour 1 portion, let all the water drip through to one cup, then change the cup and repeat the process.

Technically, this will probably be a different pour-over technique than what you would usually use. But this seemed like the simplest and easiest way to do the experiment. If you like you could try swapping out cups during your normal pour-over process, but its probably going to be a little bit busy.

As an extra step, I got another cup repeated the process with this one after all the others. So essentially I brewed some coffee with already used coffee grounds. This will let me know if theres any goodness in the grounds which I usually would be throwing away. This might give me some indication of what over extraction would taste like.

The Results

Let’s first look at the brewed coffee.

50g each of the first, middle and last parts of the 150g brew water. And extra 50g brewed after the 150g.

It is as expected but the first one is quite noticeably darker, and gradually gets lighter as the brew progresses. The last part almost looks like tea. This was a bit difficult to tell, but the viscosity of the coffee seemed to change as well. The first one looking ever so slightly thicker than the others

I would stay that a normally brewed cup of 150g looks something between the first and the middle cups.

As you can see the last cup and extra cups look pretty much alike.

Another shot from the side.

You may notice that the first cup looks to have less liquid in it. And you would be correct. Since I measured the amount of water going in to the dripper, a significant amount of the first portion would have been sucked into the coffee grounds. This is the amount you see missing from the first cup.

Another thing to note is that, since the middle and last cups seem to have equal amounts, we can guess that the grounds suck in water pretty quickly. It’s not a gradual process.

Taste Test

I expect the latter cups to be weaker, so I started to taste in reverse order.

The last 50g

When I put my nose close to the cup, it smelled of water, more than coffee.

It had a very very faint taste. But I would not say that it tasted bad.

From the looks of it, I expected a bit more taste from it, but all I got was a very slight acidity and bitterness.

The middle 50g

This smelled and tasted like a normally brewed cup of coffee.

The balance of acidity and bitterness was good, it was simply a tasty cup.

The first 50g

This cup surprised me the most. I did expect it to be the strongest, but it actually was way stronger than I had imagined. Its aroma was strong and very rich.

The taste was very strong and sharp lemony fruity acidity. I do feel some bitterness but is was over powered by the strong acidity. It really bursted in my mouth.

The beans I used was quite a lightly roasted fruity coffee, but it didi still amaze me that there actually was so much extracted at the beginning of the brew.

The extra 50g

This one smelled exactly like the grounds left in the dipper after a brew is over.

It doesn’t taste like much but it simply was not good tasting. When drinking it it does have some smell to it so I could tell this wasn’t just water, but really taste was non-existant.


This is a subjective observation but I felt that the difference between the first 50g of the brew contained about 70% of the coffee. It’s was a steeper decline than I was expecting.

One interesting thing was that the last part had nearly no flavor to it. So in the sense of extracting stuff out of the grounds, it’s likely that the last 50g is contributing very little. I suppose it does act to adjust the strength of the overall cup.

Put differently, I would guess that if I brewed 9g of coffee with 100g of water, then added 50g of just water to the cup, I would not be able to tell the difference.

Another finding was that the extra 50g didn’t necessarily taste bad. It just didn’t have a taste. I was expecting over-extraction to make it taste bad. but from this experiment I did not find this.

This is a very easy and quite interesting experiment, so if you have a bit of time please give it a try! I would love to hear your findings!