Spurting at end phase of espresso extraction

#1: Post by **wearashirt** » January 21st, 2016, 11:11 am

HI all! Without much background explanation, I would just like to directly ask what is the spurting that happens towards the end of some of my espresso shots that I observe

Start -- dripping
Middle -- continuous dark red glow with tiger stripes
Blonding - brief
Blonding 2 - spurting, probably crema matter coming out. But why is the extraction spurting?

Basket: 20 VST
Dose 17g
Out: 40g

I happen to have low head space due to the thick dispersion/shower screw. Could it be that after middle-phase of the extraction, the puck has risen slightly and has gotten pierced by the screw head?

#2: Post by **brianmch** » January 21st, 2016, 2:42 pm

sounds to your pressure is rising fast at the end of the extraction.

There are several things to consider.

Could be that your puck is falling apart somehow, maybe due to the dispersion screen, maybe not. Look at your dose, distribution, and tamp. How much screen is printing on your puck if any? Is your coffee fresh? How long is your extraction taking?

#3: Post by **mdkmdk** » January 21st, 2016, 9:04 pm

Could you post a video? Sounds like it might be an underfilled basket if I understand you right.... but I probably am misunderstanding....

January 22nd, 2016, 8:42 pm

brianmch wrote:sounds to your pressure is rising fast at the end of the extraction.

There are several things to consider.

Could be that your puck is falling apart somehow, maybe due to the dispersion screen, maybe not. Look at your dose, distribution, and tamp. How much screen is printing on your puck if any? Is your coffee fresh? How long is your extraction taking?

I can't find any evidence on the puck though because it comes out nicely when I knock it out. There's no printing of the screw at all before the shot. Coffee is waited out at least a week before blending and serving. Extraction is about 30-35 secs? I wonder if it's in the machine?

#5: Post by **brianmch** » January 26th, 2016, 11:22 am

Dunno.

Maybe that video request a couple posts up could elicit a more informed response.

January 28th, 2016, 12:07 am

The spurting has stopped since replacing my grouphead screw/dispersion screen screw with a countersunk version.

Thanks guys.

#7: Post by **trumz** » January 28th, 2016, 2:05 am

What exactly did you install??

January 28th, 2016, 7:45 am

Kyle, I installed an m6x16 screw stainless steel screw. Its head is flush or countersunk, so I now have more headspace. However, it's not OEM. Thoughts?

#9: Post by **trumz** » January 28th, 2016, 11:17 am

But if your coffee bed wasn't hitting the screw in the first palce like you said, isn't it odd that a new screw fixed the problem? Eitherway, I'm happy for you that all is well again.

I removed some metal from the screw with an old, coarse sharpening stone.

By the way, what grinder are you using?

January 28th, 2016, 12:50 pm

It wasn't hitting the screw, yes. But just little more nudging, it would. So I wouldn't be surprised if the bloom of the bed eventually hit the screw, mid-extraction. I recently handled an Aurelia, and saw that it already came with flush screws. Also, the positioning of the gasket where it tightens starts on the 5 o'clock side, as opposed to the Appia where the gasket tightens on the 7 o'clock side.

I'm using Heycafe grinders. Manufactured in China, designed by an Iranian engineer. Not the most sophisticated, but helps produce satisfactory coffee. (After 3000+ shots, the burrs may need replacing soon. I''ve spotted some nicks.)