Second shot pulls faster than first

[HB-Wantabe]

Hello everyone. I could really use some help.

When I pull two shots back to back, with time enough between to clean and fill the the PF, the second shots pulls 10-12 secs faster. Not a nice stream either. First pull is 22-26 secs. This has been consistent over a long period of time. I have a system that I follow to reduce the variables.
I have tried grinding the 2nd shot finer. Also increasing the coffee volume. Still.....problems.

Any ideas or suggestions? My equipment is about 2 yrs old. Works the same as it did when I got it.

[cafeIKE]

Macap is M4?

Do you leave coffee in the hopper?

Is this at the start of the day?
If so, do you grind a few grams to clear out the detritus?

[HB]

Have you read 1st pull of the day a beaut, 2nd not so nice? Sounds like it could be the same problem. To add to Ian's list of questions: What about the third? How are you dosing (volumetric or weighing)?

[peacecup]

I've noticed the same sometimes, and have suspected that hotter temps pull faster.

[HB-Wantabe]

Thanks for the tips and the link. My issue is the same.

I only grind the exact +/- amount that I need for each shot. I do not weigh. I typical use the same grind setting, quantity allocation and tamp method. (reducing the variables)

I still don't see the difference since my methods are the same for both shots. The only difference could be the wet PF. I have tried both wet and dry and found no noticeable dif.

I had suspected PF or group temp. I flush the group before the each shot.

My grinder did not come with a built-in grind marker so I made one. I grind a variety of beans and the marker allows me to color co-ordinate the grind points for quick reference.

I assumed the grinder was consistent. I'm surprised to hear otherwise though that was my suspicion. Just seems strange.

[HB]

When I pull two shots back to back, with time enough between to clean and fill the the PF, the second shots pulls 10-12 secs faster. Not a nice stream either. First pull is 22-26 secs.

Let me back up. Do you have a bottomless portafilter? A pour time difference of 10-12 seconds points to massive channeling.

I grind a variety of beans and the marker allows me to color co-ordinate the grind points for quick reference. I assumed the grinder was consistent. I'm surprised to hear otherwise though that was my suspicion. Just seems strange.

I think Ian was alluding to inconsistent usage of the grinder, e.g., a mixture of old and new grounds or two different coffees.

[HB-Wantabe]

Let me back up. Do you have a bottomless portafilter? A pour time difference of 10-12 seconds points to massive channeling.

BPF? Yes. Channeling is common. Sometimes just a very fast, sloppy pull that splatters the backslash of the machine.

I think Ian was alluding to inconsistent usage of the grinder, e.g., a mixture of old and new grounds or two different coffees.

"Old and new grounds"? Sometimes. Only on first shot. It will slow down the pull time. "two different coffees? Seldom. I will experiment once in a while

[cafeIKE]

If you are filling the grinder on a per shot basis, try grinding half a dose before the first shot of the day to clear out the detritus. There is a LOT of coffee hanging about that has dried out and will end up in your first shot. Use a chopstick or BBQ skewer to remove the last of the dose from the throat on each shot. Use a bottle brush to clear the throat after the last shot of the day to remove as much as possible.

ANY time you change beans, grind a full dose straight into the bin and start dialing in from there.

The MC4 is VERY consistent. Beans are VERY inconsistent. SO often require a much different grind than a blend. Changing back and forth between several coffees is going to use a LOT of coffee to get consistent results.

[malachi]

Definitely sounds like you've got old coffee trapped in the grinder.

Other possibility... do you per chance put the coffee for both shot into the grinder at the same time, grind and dose and pull one, and then repeat for the second?

[cafeIKE]

Just ran this little test on the MC4 with the heel of the roast we've been using all morning:

With just enough coffee for two shots [using BBQ skewer to clear schnoz each shot]:

1st Shot : ~17g to get the same pour time as ~14.5g
2nd Shot : ~15g time is ~15 vs ~30

for shots ground with ¼+ pound in the hopper

[HB-Wantabe]

I do not weigh the beans or grounds. I try to be consistent with the process.

Why is it always the 2nd shot not the 1st? Old grounds in the grinder slowing down the 1st? If that is the case, why does it happen even when I have cleaned the grinder (as described below)?

Tonight I will try grinding a few beans and throwing out the 1st stuff out of the grinder. I guess I should set the grinder to 'Finer'.

I use a chop stick and a basting brush to clean the schnoz and the doser between coffees. I clean the schnoz with the chop stick then turn on the grinder to blow out the remains, re-chop stick it and use the brush for final clean. Are there still grounds trapped in the grinder?

[Randy G.]

I read through this thread, so excuse me if i missed the answer to this question:

Do you... (pick one):
1- fill the hopper with your roasted coffee beans and grind per dose as you need it.
2- dose the amount of beans for each individual double shot into the hopper.
3- dose the amount of beans for two doubles into the hopper then grind per pull.

[HB-Wantabe]

2 and 3 both apply depending on how many shots I'm going to pull at the time.

Beans are not stored in the hopper.

[malachi]

Popcorning. When the volume of beans in the hopper gets very low, you will experience what is commonly called "popcorning" (both Ken Fox and I have commented on this issue in the past). If you put coffee in for two shots - as a result the grind quality will change from first to second shot. One of the reasons I argue for keeping beans in the hopper.

"Cleaning" the grinder doesn't get rid of trapped coffee. I'll never forget the first time I pulled the burrset out of a grinder and saw what was trapped in there!!

[cafeIKE]

2 and 3 both apply depending on how many shots I'm going to pull at the time.

2 can work if you grind a bit, say 2 to 5 grams [½ scoop] at the start of the session to clear out the left overs. More if changing coffee.

3 will never work unless you change the grind for the last 1 or 2 shots.
Assuming grinder is dialed in on 1 shot load in hopper, -1 full [360°] turn coarser of the micro adjuster for each extra shot loaded up to about 4. Of course, YMMV

[Psyd]

3 will never work unless you change the grind for the last 1 or 2 shots.

Pulling the entirety of the coffee and putting it back into the hopper will mix the grounds from the last bit with the rest of the grounds. Shouldn't be that much difference from your regular doppios at that point.

[Randy G.]

2 and 3 both apply depending on how many shots I'm going to pull at the time.

As mentioned, popcorn-ing can be a factor. Try this: grind enough for two doubles all at once. Transfer the coffee to another container and mix thoroughly without compacting. Now dose as you normally would and see if the two shots pull the same.

[cafeIKE]

Pulling the entirety of the coffee and putting it back into the hopper will mix the grounds from the last bit with the rest of the grounds. Shouldn't be that much difference from your regular doppios at that point.

¿Que?

[Psyd]

Que?

What Randy just said. Instead of thwacking as the grinder grinds, just pull it all into another container and and then dump it back into the doser. While there is going to be some differences between the early grind and the later part of the grind, those two small differences will be evenly (ish) distributed between the separate doses when re-thwacked. While I would never advocate the use of two different grinds to make a doppio, the two variations are so small as to be almost imperceivable.

[cafeIKE]

Ah, doser. That makes sense.

...putting it back into the hopper...

had me confused