I have just bought a gaggia baby class dose, ascaso grinder. Seem to be pulling doubles ok but having a nightmare with the singles. do I need a different grind for the single basket than the double.I am dosing to the top on both baskets, tamping with the same pressure, but the single shot comes out black and watery whereas the double has a nice crema and taste's ok. Please advise as I am going through beans like a madman.

Hi merts,

generally it is assumed that single baskets are quite hard to tame, especially with no preinfusion. For starters you might want to grind finer as less coffee means less resistance, so you need to compensate for that.

Regards,
dsc.

Cheers Tom,
Tried what you suggested using a finer grind, slight improvement but still not getting a good shot, still dark and no crema. Any more suggestions welcome. I think I would be better off just throwing the single basket away and sticking to the double.

There's a good description of the process for pulling singles here:

http://www.home-barista.com/vibie...mance-singles.html

Basically, you have to grind finer and be very careful about your dosage. Too much coffee in the basket can lead to the top of the puck hitting the shower screen, which leads to channeling. Too little coffee will make it hard to tamp properly because the tamper bottoms out on the inside of the basket. You need to get a good digital scale and experiment until you find the optimum dose. Then dial in the grind.

Or you can just stick to pulling doubles, which is what I do.

Dose is the key for singles. You have a very narrow dose range. With a double you can put 12-18 grams in the basket, with a single basket you are going to have about a half gram tolerance. The shape and shallow nature of the basket force you to be very accurate. I rarely get out a scale, but when I pull singles, I do weigh them simply because I do not pull many. I cannot eyeball the dose because I don't have enough practice. I should pull more singles, they do have a different cup than a double and are worth the work. I find the nickel test, which I outlined in the above VBM article link to be very useful in getting the starting point, then make half gram adjustments to get the right volume.

Is your Gaggia Over Pressure Valve calibrated to proper brew pressures? If not, the smaller volume of a single shot will push your brew pressures (likely) over 12 bar. ....hard to get a good shot brewing at 12 bar.

Cheers Guys for all your advice,
Being a novice, I was wondering if the shape of the basket make's a difference. My double basket has steep sides to it, and the holes in the bottom extend across the whole of the basket, whereas the single basket has sides that are angled at roughly 45 degrees, and the filter holes are mainly in the centre, (excuse the spelling of centre as I am English) could this be the problem or am I just clutching at straws

Straws. That is a common single basket shape. There are some variations in single basket shape but that is the most common. I will stand by the dose as the starting point. A little to much and the coffee cake scrapes against the shower screen causing fissures and channeling, be it horizontal between layers of the puck, or directly vertical. They also tend to take a slightly finer grind than your double basket. Again, these are grouse generalizations and do not take things like pump pressure, temperature, distribution etc into account. Any one of which could also be the culprit.