I've had my Gaggia Factory for about a week and half now and have pulled 2-3 pounds worth of practice shots. I have found that I get a better quality shot with my single basket than with the double. It has more body, more crema, and a better taste.

Whenever I pull a double, I grind the beans to the same level of fineness (as fine as my Baratza Maestro will go) and tamp with roughly the same pressure (if not more) as I do with a single. I pre-infuse for ten seconds, pull slowly down till I reach the 1/3 mark, re-raise the lever for 4 seconds, and pull the rest of the shot.

By the time I get a little more than 2/3 of the way down on the second pull, the extraction begins to blond (with large bubbles). The crema in the completed double shot usually dissipates after 30 seconds, compared to 1½+ minutes with a single shot.

What causes these differences between the single and double shot? What might be some remedies to my extraction problems?

Thanks in advance for any pointers you throw my way and any theories to explain why this is happening.

Ps. I use freshly-roasted beans (no more than a week old), and I have tried different varieties/roasts with the same results.

Hey Jamhat,

I would also like to hear what the group has to say on this as I have the same problem with my machine . Exactly as you describe , I know that they are not pressurised so that is out but the shot is better by far .

Thanks

TCF

I have the same machine (different badging) as you. I have had the same thing happen, and still do from time to time. In my somewhat limited experience, it seems to be worse if I updose (by tapping down during the grind cycle) or if I over tamp. I think it's basically a bad channeling problem. In my mind's eye, I think of the puck holding out for the first bit of the extraction, but then a fissure develops that leads to a path of least resistance early blonding. I'm not a big fan of puck-ology, but do you have big cracks in it when you remove the portafilter?

I've lightened up a bit on the dose, a bit on the tamp (or same tamp with coarser grind), and gotten better results without early blonding. I'd be interested to see if you could meet with success in this manner (would lend some validity to what I'm doing!)

Keep at it...

Hi Derek,
Thanks for the response. To answer your question about my puck - it's as hard as a brick and solid. Often times it is even difficult to knock out of the basket. There are no cracks in them and no VISIBLE holes from channeling.

Regarding channeling, however, I do recall reading a post that talked about side channeling - maybe excess water is seeping through on the outside of the circumference of the coffee bed.

Maybe I am tamping too hard. I am sure I use more than 30 lbs. I felt that I have had to do that because my Baratza does not grind as finely as a Rocky, Zass, etc. Next time I'll lighten up on the tamp and see what happens.

I agree with Derek. Sounds like you are channeling to some degree or another. Jim Schulman put together a very nice study (sorry no link) about the solids content in a cup vs dosing and it went UP as dosing went down. Flavor correspondingly followed the solids content. I suspect you are overdosing. Without room for the puck to expand, you are forcing the water to find the path of least resistance, i.e. side channeling probably.

As a rule of thumb, I have found I don't change my grind between single and double baskets, or in the rare case I need to, I go the OTHER direction from what you did. Meaning, there is less of a filter bed in the single, so it needs to be finer to reach the same extraction time. You went the other way.

Based on what I got out of Schulman's study, here is how I dose. I grind directly into my PF, with a small mound on top. I tap it on the counter ONCE. I level and tamp. That is it. More than once and I am overdosing from a flavor and blonding perspective.

On a similar note, I don't make tamping a variable to extraction. I use grind fineness instead. I tamp sufficiently to set the grind distribution so it doesn't move with the water hits it. Finally, instead of a 1/3 pull, I use 2-3 micro pulls. "Pull" with about 5 lbs of pressure (weight of your hand) for about 4 seconds, raise the lever, do it again (noticing the lever doesn't go down as far), 3 seconds, raise - again (the lever hardly moves) - raise - pull at 9.0 bar, reaching 9 bar in about 3 seconds (as opposed to under a second). The reason behind all this is to get the bed conditioned with water gently and have a full group for maximum shot volume with one full pull.

jamhat wrote:.. I get a better quality shot with my single basket than with the double. It has more body, more crema, and a better taste. ...

Whenever I pull a double, I grind the beans to the same level of fineness (as fine as my Baratza Maestro will go) and tamp with roughly the same pressure (if not more) as I do with a single.

...

In my experience with the Cremina, single baskets may not take the same grind as the double; moreover, single baskets of different shape may take different grinds.

The reasons for this (if I understand Illy's chapters on the time-dependent geometry of the coffee cake, basket shape, and brew pressure) are that the single basket allows for greater height-to-width ratio than the double (i.e. a somewhat taller puck relative to its diameter, depending on dose) and its filter area is also smaller (fewer holes, smaller effective egress). As a result of these factors, ceteris paribus, the single basket can present greater resistance, requiring either a coarser grind than the double or greater brew pressure. Dose plays a very important role in this dynamic.

You might try grinding finer for the double basket, and tamping lighter. Sometimes the appropriate adjustments are micro-step adjustments, and not all grinders are up to the task, and then you must vary the dose (pulling the cup when the flow blonds) and also, to your misfortune, adjust your tamp (a slippery slope).

Regards
Timo

Wow. These posts have caused me to reconsider my approach to the double shot in the Factory. In my mind a finer, updosed, harder-tamped coffee bed would create more resistance and better crema. But, what all of you are saying makes more sense, given that the coffee needs some space to expand in the filter. That coffee needs some room to breath!

I have begun dosing less (now a 14g double) than before. The way I am gauging the dose is by putting two 7g scoops in the hopper each time I grind into the PF. It seems that the lighter dose is helping a bit. I'm still working on tamp consistency.

I'll begin to work in more variables in the coming days - lighter tamps, micro pulls. We'll see where that takes us!

So John, you get a double shot with a few micro pulls and ONE full pull?

Thanks for the input!

- James

Alchemist,
Those micropulls seem to be helping. I have been using three micropulls (yes, the first one is the easiest, and then the leaver has more resistence each time) and then one long, constant pull. My shots have a little more crema and depth in the flavor.

I imagine that the micropulls help along the preinfusion process, soaking the entire coffee bed. Then the coffee expands and creates a better seal in the filter, allowing for more pressure.

Thanks for the tip. I plan to keep my on it for a few more days.

Thin crema (especially if there's a blank patch in the middle of the cup) can also indicate that the temperature of the brew water is too hot.

Regards
Timo

jamhat wrote:I've had my Gaggia Factory for about a week and half now and have pulled 2-3 pounds worth of practice shots. I have found that I get a better quality shot with my single basket than with the double. It has more body, more crema, and a better taste.

I apologise for confusing the discussion but allow me to suggest that the machine you have and perhaps many home lever machines were in fact designed to make shots with a single pull using a single basket. I have two lever machines and when I want an espresso I use single basket / single pull and get results that I like a great deal. Said differently, trust your taste buds not concepts.

KS