The Slayer shot profile.

 This is another famous espresso style which many baristas try to emulate on their coffee machines.

It was made famous by the "Slayer machine"

The Slayer is one of those holy grail machines. They are hand made in Seattle since 2007.

+ Video

This pic is of a single group version with a saturated group head.

 What truly sets Slayer coffee machines apart from the rest are their patented  mechanical needle valve. 

In the video Slayer show how to vary the flow rate with the paddle which adjusts the valve. 

The flow can be varied between 

55g-60g/30sec for more developed coffees (dark roasts).

45g or 50g/30sec or medium roast coffees,

40g - 45g/30sec for light roast coffees.

This valve was created to control the flow rate

and gives you the ability to adjust the water flow during the pre-infusion stage.

The pic below is from the excellent Decent app.

https://decentespresso.com/downloads

What the graph above doesn't show is the flow.

A slayer shot puts water slowly onto the puck (2mls/sec) for typically 25 - 40 secs.

(Its very different to a Londinium shot).

You can try to emulate this with any machine which allows you to control flow.

Breville dual boiler users can do a Slayer mod.

The example below uses a modified Rancilio Silvia (Gaggimate).

Of course, the Gaggimate, Gagguino and Decent don't have mechanical needle valves. 

My Rancilio-Gaggimate for example, manages flow by adjusting the vibratory pump's duty cycle through a solid state relay (SSR). It integrates a pressure transducer and a blue-tooth scale which can monitor flow.

But I do have a E-61 with a needle valve so this might be the closest I can get to a Slayer without buying a real one

https://slayerespresso.com/dialing-in-the-slayer-espresso/

In the above link, Slayer recommend this as a general starting recipe:

Use a standard basket with 18-20g size (dose should be within +/- 10% of the basket size)

Brew temperature: 93c

Pump Pressure: 9 bar

Needle valve flow rate: 50g/30sec

Ratio: (1:2) 19g in, 38g out

Pre brew time (pre-infusion) : 25 secs

Brew time: 25 secs

Total contact time: 50s

The Slayer profile I'm using at the moment is slightly different. It's called "Slayer Flow". 

It has two phases:

1. Pump more = Flow

   duration 30s

   pressure=0

   flow = 2g/s

   valve = open

   Ramp = instant

   Temp = default

2. (pump mode = pressure)

   duration 60s

   pressure 9 bar

   Temp = default (zero)

   Valve = open

   Ramp = instant

   Temp = default

To summarize:

It uses very low initial pressure (zero) & flow (2g/s) during pre-infusion.

At the end of this time, the puck is fully saturated and the pressure will rise.

You only end the pre-infusion when you see the first drops of coffee at the bottom.

I programmed the first phase to last 30 secs, but I seem to get the first drops at 15 secs ... so I think I need to grind much finer (or use a slower flow).

I was using a DF64V at setting 15 @ 1300rpm. I could also increase the speed to increase the fines.

The nice thing about this is that it addresses solubility, esp for coffees like light roasts (where you need more contact time). The puck releases CO2 & gently expands in the basket. ... less chance of channeling. Which leads me to the question... should I use a puck screen or not? I don't know the answer.

Because prefusion takes so long, there will probably be a difference in water/coffee contact between the coffee at the top and the coffee at the bottom of the puck.

The coffee at the top might have been in contact for  30 secs, while the coffee at the bottom only 1 sec. ???

This gradient between the top and bottom might result in an uneven pre-infusion.

(The top might be over extracted, while the bottom is under extracted.)

But maybe with my current grind setting, this isn't such a problem. I'm getting the first drops at only 15secs with zero pressure.

Anyway, this pre-infusion is followed with a full pressure (9 bar) extraction.

Some baristas might choose to reduce the full extraction pressure slightly (e.g., 6-8 bar) to further enhance the effects of the pre-infusion. 

This shot was 18g in, 48g out.

I was aiming for a 1:2.5 ratio but of course there are no firm rules for this. If it tastes good for you then you've succeed.

This is an earlier shot I did with the same beans but a coarser grind.

I manually stopped the shot at 48g but if I can prefect the grind this should be automatic.

In summary:

A Slayer shot on a standard espresso machine involves mimicking the Slayer machine's two-stage brewing process, which includes a low-pressure pre-infusion and a full-pressure extraction. 

This technique aims to highlight different flavors and textures in the coffee by gently saturating the puck before full extraction. 

While Slayer machines have a needle valve for precise flow control during pre-infusion, standard machines can achieve a similar effect using techniques like a slow fill or a low-pressure pre-infusion. 

I also have a e-61 with a needle valve flow control which I will try in the future.

I'm not certain the difference between this vs the slayer valve.

Use a 2-bar pre-infusion (for 20-40 seconds) and then move to full pressure extraction for another 12-13 seconds.

The total shot time is long in some recipes, aiming for more than a minute.

Some baristas choose to reduce the full extraction pressure slightly (e.g., 6-8 bar) to further enhance the effects of the pre-infusion. 

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