We are truly down the path of learning how to make the tastiest coffee, with our BRUA. We have covered all the fundamentals to pull some fantastic shots.
Today, it's time to cover a step that, while not a necessity, has the ability to level up our shots. We are talking about puck screens & paper filters. A favourite method of ours here at team Newton Espresso.
Puck Screens - What are they and what do they do?
Chances are, if you have scrolled through some coffee accounts on social media you have seen someone using a metal screen on top of their coffee bed. This is what we are talking about when we say puck screen.
Puck screens are small metal mesh disks with a diameter the same as your coffee basket (for us here with a BRUA, that's 51mm). Placing them on top of your already prepared coffee bed aids in water dispersion from the shower screen and keeps the group head of your equipment much cleaner (not that the group on the BRUA gets as dirty as a traditional machine, it's nice for it to stay even cleaner).
Over the past month, we have been taking tests with and without the puck screens on our BRUA. Our overall finding is that while it is not a necessity, it seems to have created less channelling in shots. While you can achieve the same results and the same tasting shots without it, it increases consistency.
To put it simply we didn't get better tasting shots, but more of those better tasting shots. It's all about controlling the variables and increasing our consistency.
To use a puck screen, simply distribute and tamp the coffee bed (in case you missed it, we covered all that here). Then place the puck screen on top of the bed, lock in the basket and complete your extraction like normal.
The only downside to the puck screen, they do get dirty and require cleaning, otherwise they can impart unpleasant flavours to your espresso. Similar to how a traditional espresso machine can create bad-tasting espresso if it's not cleaned properly.
We recommend rinsing after every use and once a week soaking in a small amount of espresso machine cleaner and hot water to remove built-up coffee oils, then rinsing thoroughly. This will keep them clean and produce tasty cups.
Using paper filters in espresso is still fairly new in the world of coffee.
The results are incredible and baffling all in one. The use of paper filters in the bottom of the espresso baskets has not only levelled up espresso extraction more than anyone could have imagined, but they have also inspired a redesign of coffee baskets. Using some of the principles discovered with using paper filters, high extraction coffee baskets are now being produced by many manufacturers, creating tastier modern espresso.
So let's delve into paper filters, what they do, why we love them and how to use them correctly.
Start by placing a paper filter in the bottom of the basket before adding your dose of coffee, then prep and tamp as per normal. Ok, we know what you are thinking, it's going to filter out some stuff and the extraction will go slower, right? Don't worry, when we all started experimenting with paper, we predicted the same thing, it would slow the extraction down, and we most probably will need to grind courser to compensate.
Surprisingly enough, this is not the case, in fact, the coffee came out remarkably faster, making us all question simple science and how the world works, but hey that's coffee for you! With a deeper dive into what's going on in the coffee basket, it all starts to make sense.
The paper filter acts as a small separator or spacer between the coffee & the bottom of the basket. This small gap actually allows the coffee to run faster through the holes of the basket. Having particles pressed hard up against the holes reduces the exit flow of the liquid immensely.
You may notice that, with traditional baskets, the holes don't continue right to the edge. Coffee on the outer edge near the basket wall, is usually under extracted as most of the water runs closer to the centre. The holes in the basket direct flow this way, as water that flows near the basket walls, needs to move towards the centre to exit. The paper filter creates an even exit for the extraction on the entire bottom of the coffee bed. It then flows through to the basket, in the small gap in between the paper and basket and flows out quickly, as hydraulic resistance is reduced.
Water can now run directly through the coffee (and with faster flow), contributing to a much more even extraction. This is why you can grind finer, up the extraction and have no unpleasant flavours in your coffee.
Ok, so that may have been a lot to take in. What we need to take away from the above. The water flow is more even and flows more freely when exiting. Creating more efficient and tasty extractions.
How to use paper filters correctly.
Paper filters are one of the best improvements you can make to your coffee, with the smallest possible investment. It is important that when using this technique, we follow these steps, so they work correctly.
- Place the paper filter in a dry clean basket.
- Gently pour a small amount of water from your kettle. This will seat the paper filter on the basket.
- carefully tip out any excess water and seat paper with your finger, ensuring it is centred, even and firmly against the bottom of the basket.
- Dry any water on the side wall of the basket using a towel or microfibre cloth. (It is important that the sidewall of the basket is dry, moisture on the bottom near the paper filter is ok.)
- Add coffee-to-basket and continue your usual puck prep routine.
- Pull shot as usual.
If you keep your grind size the same as you usually use, the extraction will come out a little faster.
Amazingly, when testing the TDS (Total Dissolved Solids) we extract from the coffee using a refractometer, it can still be the same or higher than normal in much less time.
You can grind finer to slow the extraction down and increase the extraction yield. Or keep the grind size the same if you are enjoying the coffee this way. Remember taste is what counts at the end of the day.
I usually find a good place to dial into is, 15-30 seconds of pre-infusion (where we push the lever until we have some resistance and hold it there for the pre-infusion time). Then continue pressing the rest of the shot in 20-30 seconds for a total brew time of 50 sec - 1 min.
As always, see what works for you and the coffee you are using. If it tastes good it's working, if not try going finer/coarser, changing the pre-infusion time, or alternatively increasing the yield in your cup. We will be covering pre-infusion and different ratios in our upcoming posts, so don't worry if you need more help with these topics.
This post has stepped us into the more advanced side of espresso extraction. It can feel like information overload, but don't worry, it all starts to make more sense in time.
If this topic is daunting, don’t stress.
All of these techniques are about levelling up your espresso workflow so you can make fantastic coffee at home, armed with expert knowledge.
Perhaps this blog is something you save for a lazy Sunday morning when you want to experiment and you have some extra time.
The main thing is to try it, have fun with it and enjoy the journey. No one became an expert overnight.
Don't forget, we are here to help! If this topic, or any of our other topics are hard to get your head around, or you simply want some more information on parts, reach out on social media or through our website contact form.
Until the next instalment, enjoy your coffee and have a go at using a paper filter on the bottom and a puck screen on top!
Lars and the team