# Gaggia Classic Pressure



## Milesy (Mar 8, 2012)

Hi folks I have been over at home barista but found this forum and figured it might be useful to get a UK perspective on things.

I have a Gaggia Classic and finding it very hard to get a pour at lower doses which does not channel. I am being very delicate with my grinding and dosing by weight of fresh roastly beans (MC2 grinder), distributing and then tamping yet from 20g downwards I get terrible chanelling no matter what I do or what technique I use.

Before I was grinding my own I was using pre ground (yes I know haha) and found I needed to dose 22g of the stale stuff to get an acceptable (relatively speaking) pour.

I want to go for smaller doses for smaller caffeine intake but also for the sweeter shots I have tasted elsewhere.

I was pointed to the pressure adjustment and I am looking for some advice on doing this. I have the steps to physically adjust it so that is not the problem.

Is there an initial adjustment that most people can make without a gauge that can get them closer to the target pressure until a gauge can be obtained or built?

Secondly, is there anyone willing to sell me a modified PF or the parts nessessary? Or can I get the parts from say screwfix myself to do this?

Lets get the pressure right then I can work on everything else.

Thanks folks


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## chimpsinties (Jun 13, 2011)

But if others (myslef in cluded) can get good shots from the classic without channeling then maybe it should be a case of getting everything else right THEN worry about the pressure.

How are you distributing? How (exactly) are you tamping? What basket are you using?

The slightest fault in your tamping could be causing channeling or a clump lower down in your basket that isn't present when coffee is stale from preground.

Give us a bit more info and we'll see if we can help you more. Maybe pics or a video...


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## Milesy (Mar 8, 2012)

I am using a double basket (non pressureised) which actually holds 22g levelled off. I do not know what the advertised capacity of the basket is, and I am using a bottomless PF.

I distribute the grinds using a fine needle once dosed in grounds by weight. I then tamp in one single even straight down tamp. I have tried the midway dose tamp, the nutation tamp, the tamp thrice method, the NESW tamp.

I get an an absolute perfect pour and flow with:

Overdosing the basket and with a courser grind

stirring with needle.

Level off in four directions. (gives approx 22g in the basket)

One single 40lbs tamp.

Quick loosen of the grounds at the sides with my finger.

Quick polishing tamp.

No chanelling or gushing.

When I use a finer grind at 16g the puck always has a big worm hole. The pour always starts slow, starts good with good striping and then it blows.

thanks


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## Milesy (Mar 8, 2012)

Without the gauge I have made an educated guess and turned the opv 270 anti clockwise. Before I done this when I activated the pump the water blasted out the group head in an uncontrolled way. Now it comes out pretty controlled and towards the centre of the group head. I am trying to obtain a gauge and down size coupler to test.


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## tribs (Feb 21, 2012)

Do a search for 'OPV mod'. You should find plenty of info.


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## Milesy (Mar 8, 2012)

Ok I ran a 16g shot using the adjustment, with my normal distribution and tamp.

The pour was much more controlled. I didn't have a massive cone nearly touching the shot glass. I had a tiny little side blonding but no spraying and no gushing.

Before the adjustment when I turned the pump off I got a massive spray in the face from the little overflow pipe as well. I was bracing for the usual spray in the eye and I didn't get it!!

Looking good. Have a plumber friend who has a gauge and looking for the right coupler for my regular portafilter.


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## matsnor (Jan 20, 2012)

May I suggest leveling off after doing the general distribution with the needle? The way I do it is overfill the portafilter slightly, WDT within the portafilter, THEN carefully level with a straight 90 degree angle item such as a kitchen knife, shuffeling excess coffee off the portafilter rather than compressing it down. When the surface is perfectly even, I tamp by first carefuly placing the tamper down on the portafilter in a proper angle, and while ensuring that all the angles are proper i press down with a small twist at the end, applying about 30lbs or so of pressure.

I get some pretty decent shots, and there is no channeling issues when I use this technique.


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## Milesy (Mar 8, 2012)

Hi. I already do that as mentioned above but my basket takes 22g when levelled off. That is too big a dose for me. I can perfect pours at 22g, distributed and levelled but I am trying to 16g-18g doses.


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## MikeHag (Mar 13, 2011)

Sounds like you're on the right track to me.

Personally I don't like the MC2 grind much, and think it encourages grinding too fine. If you're grinding even finer to compensate for the dose reduction, that could be creating a bed that is difficult for the water to perc thru, so it eventually punches a hole. If your machine pressure were reduced, that might help overcome the issue.

(Or get another grinder







)

Also, make sure your shower screen doesn't have blockages.


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