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Teflon coated….(Long post)

Plethora of things are teflon coated these days. It’s on the frying pan, fabrics and recently it has been sprayed on our portafilters. It was a mission to clean the dirty dried up remains of an espresso shots, and we can’t clean our baskets and portafilters after every shot pulled. After coating the surface with teflon, only thing i do now is rinse with hot water, nothing else.

Then i came across this:

 http://www.jimseven.com/2010/09/28/teflon-coated-baskets/ 

James Hoffmann did an interesting experiment with teflon coated baskets, with a video.( Check that post first before reading on this post if you haven’t done so)

I thought by coating the basket with teflon; flow rate and extraction from coffee bed would remain the same, or would have correlation to non teflon coated basket.

I was wrong; the teflon somehow changed all things where i thought it would remain unchanged, and the video shows that.

This made me thought ‘Teflon coated portafilter is enough’, until this showed up

Yes, it is a teflon coated dispersion block for Nuova Simonelli Aurelia. This was sent to Andrew by Paul from Coffeehit (Many thanks Paul) for us to play with and test on. So on a quiet Saturday evening, i made my way to Bank, where i got to play with this little green thing 1 on 1. 

My first impression was ‘just a dispersion block with teflon’ nothing special really, except for the fact that; on the hand, it felt really smooth and silky, unlike the rough brass dispersion block.

Side by side, it looks like this

For those who does not know the function of the dispersion block on the Aurelia, put simply, hot water is jetted out from the mixing cavity at an angle; this is done so when it hits the dispersion block, equal amount of water by passes the 8 holes on the block itself, so water is distributed evenly, hence achieving good extractions from all areas of the coffee bed.

I thought having teflon on dispersion block is a good idea, as it is very very hard to clean! So i quickly fitted the teflon block on one of the group head, and started to pull some shots through and start my experiments..

Experiment 1.

Firstly, i set the grinder using our house blend, through the group head with no teflon dispersion block. When i started to get good shots through, i measured the dose, time of extraction and the brew weight on both group heads ( one with teflon one without)

So have a look below:

 So for each shot, i tried to get these variables constant:

Dose : 21g

Time: 25sec

Tamping technique 

Few things that i want to point out, or you guys already noticed is that, the teflon shots were pulled from a naked portafilter, where as brass had spouted portafilters, also, i can’t guarantee that each group head was at equal temperature, but i would imagine that it was within ± 0.5℃.

Even with these factors did contributed to the fact that; my experiment was not entirely ‘Uniform’ or ‘Accurate’ giving fair results, the results did surprise me.

17g difference in brew weight is quite big. Very big i would say. Also, when i was observing the shots coming through the group with teflon, it seemed to me that the water was not removing much soluble solids from the coffee bed, to me, it seemed to be channeling rapidly even though the shot was aligned at the centre,

here is a picture:

With my eyes only, i couldn’t explain what was happening, so i decided to let my palates take charge. The shot from the brass dispersion block tasted of everything i desired; floral notes along with apricot notes coming through, giving way to sweet chocolate notes finished with very nutty after taste lingering in my mouth.

On the other hand, the shot from the teflon dispersion block was quite unpleasant.

It felt to me as if i was drinking sour americano, flavors were underdeveloped, it was very watery in my mouth, so much dilution, i could only taste slight nutty notes on that shot.

After tasting each shot, I’ve realised that, somehow, the teflon dispersion block was not doing it’s job. It wasn’t letting water pass through the 8 holes equally, or evenly so even extraction could happen, instead channeling was occurring, not much of the water was going through the coffee bed removing soluble solids.

I had no clue why this was happening, i repeated the same experiment over 10 times but i had the same results as above.

Experiment 2

I decided to take a look on the spent coffee bed. What this tells me is how much soluble solids have been readily removed from the coffee bed. So if i pulled; nice evenly extracted espresso, the spent coffee bed should have nice graduation of color. The top of the coffee bed( where it has first contact with water) should be lighter than the bottom, and inside the coffee bed, should have nice color distribution( Light to dark from top to bottom).

Here are some pictures of the spent coffee bed:


 The spent coffee bed from teflon is still quite dark, where as coffee bed from the brass is noticeably lighter, showing that soluble solids has been removed from the top of the bed.


 From the second picture, i wanted to show the color inside the coffee bed, this picture, just like the first shows that the coffee bed from the teflon is still dark, no change in colour between coffee bed, not much solids were removed.

I don’t know, I just don’t. I know that teflon dispersion block causes or contributes majorly to channeling, therefore producing under extracted, sour shots. But i just can’t figure out why…

If i was to take an educated guess, i might say that; maybe there is something to do with friction of the dispersion block. Brass, even though on hand it feels smooth, on microscopic view of the surface will be very rough looking, so causing friction when water is flowing on it’s surface.

But if we cover that surface with teflon, are we taking away all that friction or most of it? Making the surface ‘slippery’ for the water?

I don’t know, i guess it’s up to the scientist for this one… it was enjoyable though, in the mean time, i will make sure i give these brass friends nice polish.


Comments and suggestions are welcome!! I would like to hear what other people think about this alot!

Sang ho