# Dispersion Plate Marks On Puck - Gaggia Classic



## Brewster (Jun 9, 2015)

Slightly random question, not sure whether it's necessarily a bad thing, but I'm curious...

Since changing over to the brass dispersion plate on the classic I've noticed that the puck has an imprint of the dispersion plate rather than shower screen after a shot.










Am I right in thinking this might lead to a less even extraction if the water is flying into the puck like this, and if so, what would help (lower dose, courser grind, etc)?


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## Jumbo Ratty (Jan 12, 2015)

To me that would suggest the shower screen isnt holding the water back enough and its coming straight through predominantly in the four areas that have dips in.

I have no other explanation than that as im sure you have fitted it in correctly and the showerscreen has no apparent bulges in.

I would try putting the original shower screen on and seeing if the same thing happens with that.

This may help eliminate one piece of newly fitted kit as the culprit

Im assuming you fitted the IMS shower screen at the same time


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## El carajillo (Mar 16, 2013)

How much coffee are you putting in the basket ? Once you have tamped the puck, try placing a 1 p coin in the centre then insert the P/F in the machine, remove again and check to see if the coin has left an imprint. If it has you are over filling the basket and the water cannot spread over the surface. If so reduce the amount of coffee / use larger basket.

If you are not over filling it may be just where the water exits the dispersion plate towards the end of the brew. (puck expands as coffee is wetted )


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## Kyle548 (Jan 24, 2013)

It could also be back pressure- remember that as you shut the power down all pressure will be pulled though those spots to the solenoid.

Also check how your shower screen is dispersing the water - might be worth trying one with microholes in a solid plate like IMS if your using a mesh one.


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## timmyjj21 (May 10, 2015)

The brass dispersion plate appears to have slightly smaller holes than the stock aluminium one, so it may be jetting down. Then again, I've been having issues with the solenoid not fully venting pressure ever since I changed to brass and IMS screen so it is likely the issues previously suggested. Not sure if its the grinds blocking all the screen holes during the vent or the fact that I steam with the group handle still on and remove it at the end, so would have had an elevated temp and boiled a bit, creating pressure, and blowing the handle off when I remove it.


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## Kyle548 (Jan 24, 2013)

timmyjj21 said:


> The brass dispersion plate appears to have slightly smaller holes than the stock aluminium one, so it may be jetting down. Then again, I've been having issues with the solenoid not fully venting pressure ever since I changed to brass and IMS screen so it is likely the issues previously suggested. Not sure if its the grinds blocking all the screen holes during the vent or the fact that I steam with the group handle still on and remove it at the end, so would have had an elevated temp and boiled a bit, creating pressure, and blowing the handle off when I remove it.


No, it sounds like your solenoid just isn't doing its job.

If the brew switch is off, then the group head is completely isolated from the boiler so any changes in pressure at the group would indicate a faulty solenoid.

It might be that pressure isn't venting correctly in the first place - but bear in mind that 9 bar (15?) wants to be anywhere but where it is - so pressure should equalise enough that it doesn't blow.


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## Brewster (Jun 9, 2015)

I had the IMS screen with the stock holder, so I'm sure it's about the new holder.

I'm using 18g (+/-0.3g) in an 18g VST basket.

Without the PF in the water appears to be slightly dispersed, but with a stronger flow nearer the four holder holes.

That said, I've not noticed any negative impact on the taste, so maybe it's nothing to worry about...?

@timmyjj21 I've noticed the same actually, on the odd occasion I've left the PF handle in whilst steaming - I'm just remembering to take it out now!


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## timmyjj21 (May 10, 2015)

Interesting, nice to see its not just me, but bad to see it is still an issue. The solenoid vents fine, with no backflushing issues. It seems to be only when the portafilter is left on when steaming. I used to leave it on to drip drain and stop the sloppy puck, but have had to change my routine.


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## timmyjj21 (May 10, 2015)

Since this thread popped up again, I had issues same as the OP. It appeared to depend on the type of bean I used. I fixed it by ensuring the IMS screen is positioned so it doesn't have a hole cluster directly under the brass plates outlet.

I did notice the brass plate was a fraction of a mm smaller than the aluminium and had to be careful how it was put on, as the group seal would occasionally blow out when taking the portafilter off. Not sure why i was getting pressure build-up, but it isn't an issue any more.


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## destiny (Jun 4, 2015)

@timmyjj21 I experienced the same issue with seal blow outs but nothing with the puck - perhaps as I am on the top limit of my basket.

Did you adjust the holder just by loosening up the screws and re-positioning or something else?


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## timmyjj21 (May 10, 2015)

I'm at the top limit of the basket- 17g in a standard 14g basket.

I loostend the 2 bolts and shifted the brass lump a fraction over to the side it kept blowing and that was evidently enough.

I'm now using a softer Cafelat silicon seal and I'm not having an issue, so it may be temperamental, but still get a hiss when removing the portafilter after steaming. My PID is set to 150 for steam and the group head really heats up.


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## risky (May 11, 2015)

I noticed these dimples after I changed over holders. But I get flawless even pours from the naked pf so I don't think it actually makes any difference?


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## Khashy (Mar 10, 2015)

Thread Revival.....(instead of a new thread)

Just wondering if @risky or anyone else has seen any change/done anything about the dimples over the past year and a bit since the last post on this?

I am getting exactly the same thing and am wondering if it's just a 'feature' of the brass dispersion plate and IMS shower screen combo, or should I do something about it?

Thanks,

K.


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## risky (May 11, 2015)

@Khashy I believe it to be something to do with back pressure from the OpV when the shot is killed. Refracting the espresso shows decent EY (for my gear anyway) so I don't believe it is causing channeling.


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## Khashy (Mar 10, 2015)

Thanks @risky. In that case I'll treat it as a feature and leave it at that, I wasn't looking forward to boring out/adding more holes on my brand new and shiny shiny brass plate!


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## Jumbo Ratty (Jan 12, 2015)

I think i remember someone saying if you slacken the screw off slightly that holds the shower screen in place it helps reduce the marks.

Something about the hole in the IMS shower screen that the screw goes through is smaller so when screwed in it holds the screen closer to the dispersion block due to the the screw head being countersunk


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## Khashy (Mar 10, 2015)

Right, thanks.

Right now I have the screw so tight that it would need a Hattori Hanzo sword to move it (sorry, couldn't think of a film reference for a super strong screwdriver...)

I'll try loosening it a bit.

As an aside is two shower plates (standard on top of IMS or the other way around) a stupid idea?


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## Jumbo Ratty (Jan 12, 2015)

Let us know if it helps, also, if you still have the standard screen is the hole in this for the screw to go through bigger?


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## timmyjj21 (May 10, 2015)

I drilled out my brass dispersion plate with an improvement to the puck surface. Anecdotally, keeping the shower screen screw loose so it just hold the shower screen on without compression/distortion helps a bit.


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## Khashy (Mar 10, 2015)

I loosened the shower plate holder, I think it made a tiny bit of difference but not a huge amount - this is a new feature of my machine that I shall grow to love over time...

btw the standard screen's hole is ever so slightly larger than the IMS.

I did try to put both shower plates on at the same time but I think it gets too thick for the screw to reach the dispersion plate.


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## risky (May 11, 2015)

Turns out there is a specific device called a 'ninja washer' (because it looks like a throwing star) which is designed to go between the screen and the dispersion plate. This both spaces the plate away from the screen and stops the screen bending when the screw is tightened.

No idea if it's an IMS part or aftermarket.


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## Khashy (Mar 10, 2015)

My searches for 'Ninja Washer Coffee' on google come up with everything but a shower plate device. Happen to have a link @risky?


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## MarkII (May 12, 2015)

I am having the same thing happened to me as well and i hope it wasn't a problem.


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## risky (May 11, 2015)

http://dolo.com.au/products/ims-competition-shower-screen

Doesn't seem available on its own though.


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## MarkII (May 12, 2015)

...or maybe ring washer can do?


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## risky (May 11, 2015)

Apparently it doesn't make any difference:


__
http://instagr.am/p/BCAuOwByuMN/


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## analogmonster (Feb 24, 2016)

Hi, I'm new to this. I've done OPV+steam wand mod, VST and bottomless portafilter. Adding PID soon and and IMS screen soon and just wondering what difference a brass displacement plate makes


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## timmyjj21 (May 10, 2015)

In theory the brass dispersion plate has better heat retention and thermal mass, making the inter- shot temperature more stable. Personally I like it simply because it is easier to clean.


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## analogmonster (Feb 24, 2016)

Even if the rest turns out to be subjective I'm 100% sold on the cleanliness point. The standard dispersion plate was disgusting when I took it out and Puly Caff'd it. Looking at other brass dispersion plate threads they said Puly Caff causes an electrolytic reaction between the dispersion plate and screws. Mine was in a glass container by itself and it still reacted.

So I'm buying a brass dispersion plate, IMS 200u shower screen and cafelat group gasket tonight. Thanks for your input


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