Coffee Data Science

Steam Pre-Infusion for Espresso: A Summary

Collecting some steam

Robert McKeon Aloe
Nerd For Tech


Steam Pre-infusion started because of my experiments comparing the Decent Espresso (DE) Machine and the Kim Express. Then I worked to identify some of the reasons the Kim Express outperformed the DE, and I discovered some steam pre-infusion. Then I worked to understand it, and eventually I designed a profile for my DE to try to emulate it.

Here is the outline of this summary:

  1. Comparison of the DE to the Kim Express
  2. The Coffee Sneeze
  3. The History of Steam Pre-infusion
  4. Steam Pre-infusion for the DE
All images by author

DE vs Kim Express

I felt after five months of using the DE that I should do a paired test against my Kim Express.

The Kim wasn’t just a little better; the gap was huge. I’m still using my DE on a daily basis, and I believe it could do better. I don’t know how yet.

It caused me to think I missed a variable which is why this is called round 1. I believe I can make a better profile, but a deeper understanding of the Kim is necessary.

Coffee Sneeze

Over the past few months, I’ve observed a small coffee flurry before each espresso shot.

I didn’t know what it was, but after viewing some videos, I found the initial pressure change caused a small amount of fines to blow through the puck and out.

I call it the coffee sneeze.

After my comparison with the DE and the Kim, I looked at the sneeze again. In my quest for a better understanding of my lever and great espresso, I took an even deeper look at the coffee sneeze.

Steam Pre-Infusion

Steam Pre-infusion is not a new feature for espresso machines. There is an interesting history of machines that had some amount of steam pre-infusion without it being part of the design.

I took some slow motion videos of the Kim Express and the Decent Espresso machine without a portafilter. The aim was to look at steam pre-infusion. I slowed them down even more to understand how steam comes out first before water.

The real gem in these videos is the audio.

Emulating Steam Pre-Infusion

I spent some time trying to understand steam pre-infusion, and I figured out how to get a similar effect on the Decent Espresso machine using a very low flow rate at a high water temperature.

I’m not done in trying to optimize this first step, but I wanted to share what I have to help out anyone who wanted to try it out.

I hope these tests encourage a better understand of espresso machines and impact future design.

If you like, follow me on Twitter, YouTube, and Instagram where I post videos of espresso shots on different machines and espresso related stuff. You can also find me on LinkedIn. You can also follow me on Medium and Subscribe.

Further readings of mine:

My Future Book

My Links

Collection of Espresso Articles

A Collection of Work and School Stories



Robert McKeon Aloe
Nerd For Tech

I’m in love with my Wife, my Kids, Espresso, Data Science, tomatoes, cooking, engineering, talking, family, Paris, and Italy, not necessarily in that order.