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The "warm up" shot phenomenon

Postby nixter on Fri Jan 14, 2011 3:40 pm

Well I couldn't decide which other thread to tag this on so I'm starting a new one...

I've been interested in the "warm up" shot phenomenon. That is, the theory that it takes a shot or two before things start extracting properly. I have found this to be true myself but I wonder if any of the abundant temp curve data has anything to say about it? Some say that it's actually the grinder. Fully purging yesterday's stale grinds can take at least a full dose or two of fresh beans. My gut tells me that while this is probably true that the machine also reaches a certain temp stability after a couple of consecutive shots. I *think* I see less swing on my erics therm adapter after a couple shots but that could easily be in my head. There's also been talk of the first shot being a "seasoning" shot to get the fresh coffee oils going. Perhaps it's all three of these things.

Thoughts?
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Postby espressme on Fri Jan 14, 2011 5:08 pm

Good questions! I now use a "Baratza Vario" and a "Cremina." I am concerned with the first shot as it is the only shot, most often. The grinder is filled and used as the beans fall. No prep run to purge which could leave some drier grounds in the chute. Might be a good thing to seal the basket as they expand and slow the pour? :lol:
I use a warming shot with the cremina to wash the basket of dried coffee, and also to get the group up to temperature. A temp tattler Here has been my way of checking group temp for the first shot. I located those devices and passed the sales of them to OE.
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Postby bgn on Fri Jan 14, 2011 6:29 pm

The best solution is a wife that likes lattes.
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Postby Marc on Fri Jan 14, 2011 7:00 pm

haha nice one

If you have a grinder with a doser, it may very well affect your shot.

But again, if your machine is nicely warm up the only factor left are the beans. During a day or day by day depending on your use, you'll need to adjust your flow because of the beans degassing.

espresso is finicky so aiming the first shot to be perfect would be an utopia
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Postby nixter on Sun Jan 16, 2011 2:29 pm

No doser (vario) and my beans are always very fresh
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Postby benm5678 on Sun Jan 16, 2011 3:57 pm

In my experience on the Duetto e61 & single dosing, I can't say the the 1st shot after idle for a few hours has any less chance of being amazing than a consecutive pull.

Of course, I'm referring to when no adjustments are made.

As the environment/coffee age/blend change, the first shot can often be inferior, and serve as the guide as to what to adjust for the next one... (which will be perfect of course! ;))
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Postby Javacat on Wed May 16, 2012 1:14 pm

I do believe that the factor most at play here is the grinds. I have never conclusively seen where a consecutive shot on any type of machine - h/x or dual boiler, was better than one prepped correctly on an idle machine as long as a pre-flush was employed - even if the machine was detergent b/f'd. I have actually had many of my best shots on a freshly b/f'd machine without any re-seasoning at all - goes against conventional wisdom, I know. One tip that I might add is to try inserting your p/f into the group and leaving it for 20 seconds prior to pulling your shot - I use my machine in a chilly 67F basement and have found that this improves the shots considerably - group heads radiate a LOT of heat without the p/f in place.
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Postby pizzaman383 on Wed May 16, 2012 2:19 pm

I have an e61 pid'd double boiler. I single dose and use beans within 3-4 days of pulling them from the freezer. I had consistently different tasting first shots.

After looking at what varied I found that the pressure in the brew boiler was much lower after sitting all night than a couple of minutes after pulling a shot (measured by the brew boiler pressure gauge).

The impact of this was a slower ramp up to full brew pressure. I started doing a couple of blind back flushes prior to preparing my first shot. This has made my first shots pretty much indistinguishable (at least to me) from my later shots.
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Postby mitch236 on Wed May 16, 2012 2:25 pm

You bring up an interesting point. I've always wished I could leave my spent puck in the pf to keep the heat in the grouphead but the thought of the coffee cooking for 15-20 minutes between pulling shots sounds disgusting. Since I use a bottomless pf, why couldn't I put the blind disk into the pf, run the pump to fill the basket with water and then leave that? I wonder if it would improve the temperature stability any? I haven't experimented with it since I think it will have minimal benefit but maybe I should?

BTW to the op, I don't notice a difference between my first shot and the subsequent shots but I leave my machine on 24/7
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Postby LaDan on Wed May 16, 2012 4:04 pm

I pull an empty 40-50ml water shot into my cup. Wait 2 minutes. Empty my cup and do the same again. Then I take the PF out, dry, grind, and pull a shot. These 2 shots of water stabilize the machine, brings the grouphead to temp, tells the brain of the PID that I am pulling shots so it is better get of his butt and get to working, and the machine is ready to go.

Never an issue with my first shot since I started doing that procedure. In the time it takes me to do those 2 water shots, I have the time to fill up my pitcher with milk, weigh and load the grinder with the right amount of beans, and whatever other preps needs to be made.
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