The Matrix Shower Screen - Page 5

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coffeeOnTheBrain

#41: Post by coffeeOnTheBrain »

almagoro wrote:hey!
backpressure is about 1.5 bar...
like a gicleur, the pressure drop is only during the build-up of pressure. once the pressure above and under screen is the same (requires a coffee bed), that's it. the flow has to be equal.
...

during the experiments, we worked also with screens with much higher backpressure. the change on acidity was much more noticeable
...
Thank you, 1.5 bar sounds reasonable. It is also very interesting that there was a seemingly better effect with a higher pressure drop. That actually makes me wonder why the perceived acidity changed. I would imagine that there is actually is a pressure drop. I believe that it might be neglectable at the beginning of the shot, but there needs to be a pressure drop due to the added resistor in form of the screen at the end of the extraction when the puck erodes, because the puck can not give enough resistance in that stage anymore. Therefore your shower screen might actually lower the flow to the end of the extraction similarly to what Gagne recently posted about a flow profile for espresso on the Decent machine. This theory could explain why a higher pressure drop lead to even less acidity. Maybe more espresso machines makers should talk to you ;)

bettysnephew

#42: Post by bettysnephew »

From what I am reading, I plan to try one on my Bosco when production versions are available. My screen is an E61 type so if it doesn't work well I can give it to my daughter for her VBM. I have spent far more to just try something out n this rabbit hole that is espresso, as I am sure most of us have.
Suffering from EAS (Espresso Acquisition Syndrome)
LMWDP #586

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leozava
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#43: Post by leozava »

Recently I've been seeing a crater in the same spot on my puck after every shot. I think the way the water is fed in my faema velox it "bounces" off one side of the piston and gets through the shower screen, I really have no other explanation?

Im using vst shower screen and have tried switching back through my old shower screen and keep getting the same result. Recently I started putting a paper filter disk on top of my puck amd it has completely eliminated the issue.

Long story short, I hope this shower screen will have a similar effect as the paper disk and help me eliminate that from my work flow.

Almagoro, I would have to "stretch" the shower screen just a little to get it to fit, would this damage it? It works with the vst baskets

almagoro

#44: Post by almagoro »

have you seen this
https://www.instagram.com/p/CKBQffflf19 ... _copy_link
?
made me very happy :D

to answer some questions:
leozava - i got asked a lot if it will work like adding a paper filter. the answer is - maybe? :) it will definitely help create an even flow in your puck, like the paper filter.
your hole problem is a puzzle. piston machines have a beautifully even flow thanks to the fact that they create a column of water. my guess is that the feed tube might creat a spray at the beginning of the action. again - guess. you could check it by limiting the flow into the cylinder.


coffeeOnTheBrain - the pressure drop behaves like other gicleurs. once the pressure is even at both sides of the plate, that's it. the change in perceived acidity is mostly because of a cool physical reaction that happens in the plate. the pressure is theoretically even at any plate of the system. if it wasn't , there would be differences in the flow which is not possible. however, in porous media you have micro-pressure pockets where the pressure rises exponentially and then it drops back to the working pressure. the drop in pressure causes to H2O liquid to turn into micro gas bubbles. it also causes carbonic acid to break down to water and gas - H2CO3 ---) H2O + CO2. The added micro gas bubbles help build more crema (acidic bright coffee usually have terrible cream) and the crema coats your tongue with oils, buffering the acidic tastes. there's also the reduction of the carbonic acid, but that alone can hardly be felt.

keep the questions coming!
have a great weekend!
omri

leozava
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#45: Post by leozava »

[quote="almagoro"]have you seen this
https://www.instagram.com/p/CKBQffflf19 ... _copy_link
?
made me very happy :D

to answer some questions:
leozava - i got asked a lot if it will work like adding a paper filter. the answer is - maybe? :) it will definitely help create an even flow in your puck, like the paper filter.
your hole problem is a puzzle. piston machines have a beautifully even flow thanks to the fact that they create a column of water. my guess is that the feed tube might creat a spray at the beginning of the action. again - guess. you could check it by limiting the flow into the cylinder.

Yes, it's definitely the initial "jet" of water that is causing the problem. It can be remedied by lowering the inlet water pressure down to about 1bar but I find that too low of a pre infusion pressure, it also reduces the volume of my shots quite a bit. I will take some pictures of the pucks from my afternoon coffees and report back

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LVD
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#46: Post by LVD »

For those that have had a chance to use this screen for a few weeks now, would anyone mind updating us with your experience?

mathof

#47: Post by mathof »

ojt wrote:Interesting. I am using this on top of the puck now https://www.bplus.biz/products/lower-sh ... uck-screen

I think the effect is pretty similar, definitely helps to achieve a more even extraction. Some have gone as far as completely removing the showscreen and only use the mesh.
At the link you give, the manufacturer states:

"Due to the solid metal mesh that need to pull shot with higher water temperatures (+2~3°C)."

Do you find that to be the case?

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ojt

#48: Post by ojt » replying to mathof »

Not necessarily. I had also just changed my plastic sleeve to a stainless steel sleeve so actually dropped the temperature a little. Also I don't have a K-type thermocouple to throw into the basket so I can't really verify any of it, but I have gone down from 88-90 of GH temperature to 84-86 with all the mods including the screen. Err, so what am I saying..? I guess no, I didn't find a particular need to raise the temperature, all based on taste in cup :)
Osku

mathof

#49: Post by mathof » replying to ojt »

Thanks very much. I may give it a try, when I run low on paper filters.

Verona? Una bellissima città. Sei fortunato!

lucasd

#50: Post by lucasd »

I can confirm that the matrix shower screen works very well on the lever machine.
I get quite even flow on Londinium R and no problem with draining after pulling the shot (maybe slightly slower).
It runs very clean. Now I need to observe how it will behave in a long run...