Cause of big bubble crema

[simonp]

I have noticed that all my recent shots, (except those made with Espresso San Giorgio which is quite a dark roast) have had loads of crema, but with lots of big bubbles that rapidly dissipate leaving about 5mm of lasting crema.
Even with beans that are over a week from when I roasted them are doing this, and the crema often overwhelms the spouts.
The crema is more of a cinnamony colour rather than the reddish brown that we hear about, but often has darker mottling.
Is this flufft crema a bad sign? or am I worrying too much? My recent home roast shots have not been tasting so good.
By comparison the San Giorgio, whilst a little dark in roast for my taste gave very fine red, if a little thin, crema.

[anette]

Is there a lot of Robusta in your blend? That always gives huge but quickly condensing crema, and would probably be the cause of the dark motting, too. I'm guessing the motting you describe is equvalent to tigerstripes, which, despite the following it has as a sign of a good espresso, I've always thought as a sign of overextraction and burning of the fines. Don't know. But you said the coffee wasn't as good as usual, so maybe you could try either ease up on the robusta, lighten up on the roast or try grinding coarser and dosing more. Fluffy crema isn't neccessarily a bad thing, it's just the gasses reacting and it will settle like you describe. Even a week old roast will do this if the greens are fresh enough and the structure too unstable. Let it rest, roast slower and don't worry! Your coffee is obviously alive and kicking, not a bad thing!

[maurice]

I sometimes get something like this - big bubbles that rapidly disppear. I find it tends to go with an espresso that doesn't taste as good as it should. I never use robusta, so that's not it. I generally fiddle with the grind and tamp pressure, and that manages to correct it, but as I play around with both at the same time I can't say which of them does it. And I only ever get the problem at work with a Gaggia Carezza. Never seen it with the Pavoni lever at home, though I use the same roast in both.

[simonp]

Is there a lot of Robusta in your blend?

I've been getting this with single origin beans or blends of all arabica. I tried a pre-blend (with 10% robusta) that I roasted a bit prior to the others, and this gave good red/brown crema, in fact this looked the best pour I have seen so far.

Even a week old roast will do this if the greens are fresh enough and the structure too unstable

A lot of people say that beans are stale after a week, personally I have found that it takes about 4 days for the baking soda taste to drop away, and often after 10-14 (rarely get beans last this long!) days I still get lots of crema.

Let it rest, roast slower and don't worry!

My last roast I did slower (slower to 1st crack that is) but kept the time from start of 1st to 2nd down to 3 minutes (from the 5 I had mistakenly been using), so I'll see how they come out.

[matts]

Hi Simon

I was getting this and it was doing my head in, eventually I figured out that the temperature was too high having tried everything else.

I'd succumbed to the temptation to keep turning the PID up and up a degree or two, I think it's a bit like driving on the motorway where you're just noodling along and then all of a sudden you're doing 90, anyway, I digress, I think like Annette said it was burning the fines (or something). Try turning the PID right down again to the point of nasty light tan cafe coloured crema and then working your way back up, worked for me.

Cheers
Matt

[simonp]

I recently checked my brew temp using a styrofoam cup and a thermocouple, and it seemed OK at 95C, but it might be worth dialling the PID down like you say as it's so easy to do

[phil]

IMO (and wtf do I know, you might reasonably ask) 95C is a bit hot for a default temperature, although probably good for some cases.

Some folk have reported optimum taste results at as low a temperature as 88C for certain blends (regrettably I can't remember more about the circumstances), albeit there is obviously some uncertainty surrounding the accuracy and of anyone's measurements and the equivalence of people's measuring techniques.

[simonp]

I will try lowering the temp, I've avoided it so far, as I'm running my boiler at a lower temp than most other PIDed Silvia people anyway, but with my different thermcouple location this may well be the case.
I have some pre-roasted beans coming, so they will be a good test, as at least I know the roast will be OK, which has been a questionable thing recently (Hottop profiles seems to work well though). With the roast being correct, I can then very the temp and know that good or bed results are only down to that.

Actually I have noticed that the espresso in the cup has seemed quite hot, way too hot to drng straight away.