atao wrote:manual pre-infusion: crack steam wand for first few seconds of pull (i'm convinced this is significantly improving the consistency of my shots: i'd be interested to hear from others who've tried this)

Not sure I am clear how to pre-infuse the grounds - could you please expand on this? thanks

for preinfusion, what i'm doing is to open the steam knob to bleed out excess boiler pressure. after most of the pressure has been released, i leave the valve open just a little bit, then start the pull. a few seconds after starting the pull, i fully close the valve. i believe i'm getting more consistency in the extractions this way.

jsdp wrote:The technique that worked best for me on the new generation Silvia was when I started reverse temperature surfing and hitting the brew switch about 1 min 30 seconds after the heater light goes off (which is an estimated beginning brew temperature of 201-202 degrees). I also adopted turning on the steam switch for 10 sec (5-7 sec into the pull) to help stabilize the temperature drop during the pull. Another key factor was letting Silvia warm up at least 45 minutes (preferably 1 hour) to ensure that the brew group and portafilter are up to proper temperature. The combination of these techniques have helped me reproduce a consistently good shot without a PID.

Interesting technique. I will give this a try. But wouldn't it be more logical to enable the steam switch at the end of the pull?

the idea is to start the pull with reduced pressure on the puck so it gently gets infused. so you'd want to do that at the start of the pull not the end.

No, I mean the technique jsdp described, about enabling the heating element during the brew process by flicking the steam switch (not the steam valve).

I do it too. Silvia gets water to the group by pushing water into the boiler. The water entering the boiler is cooling the rest of the water down, so the temp falls off fairly rapidly at the end of the pull. If you start your pull, and then engage the steam temp switch, as the incoming water brings the temp down, the heating element tries to keep it from getting too cool to quickly. It also give you a bit of a head start on heating the water up to steam, too!
Of course, if you wait til after the pull, you're not contributing to the espresso at all. It gets what it gets. Quite often, the water entering the boiler will cool the boiler (with my 100C stat) to the point where it wants to kick on anyways, I just get it started a bit earlier than that.

LGB wrote:Interesting technique. I will give this a try. But wouldn't it be more logical to enable the steam switch at the end of the pull?

Psyd did a good job of explaining why you would consider turning on the heating element (via the steam switch) during the pull.

Also, different espresso blends have different optimal brewing temperatures, so this should also be considered when using this technique. For example when I use a blend that has an optimal brewing temperature of 198°F, I don't use the steam switch technique during the pull. When I use a blend that has a preferred brew temp of 202°F, I use the steam swith for 10 seconds during the pull ( say start at 6 seconds and shut off at 16 seconds) for my first double. When I make subsequent consecutive shots, I may reduce the time the steam switch is on to 8 seconds (for 2nd double), 6 seconds (3rd double), etc due to the increased brew group/ component temperatures which aid in the temperature stability. Note that when you shut off the steam switch, there is residual heat from the heating element still being applied.

Remember, these additional variables and techniques should be considered and applied at your discretion with the ultimate goal being the taste of the espresso.

Joe

A couple of comments:

1. Cracking the steam valve is also a very good idea from the temperature control aspect. A Silvia shot is characterized by an initial spike in temperature to around 208F - 210F (measured in the brew path using an Eric S adapter and thermocouple). This initial spike, IMO, serves no useful purpose. By cracking the steam valve for a few seconds before pulling the shot, the spike can be virtually eliminated, with an accompanying improvement in the intrashot temp profile. This is because the short bleed allows the superheated steam/water that congregates at the top of the boiler to leave the building with Elvis before the shot is started.

2. The second characteristic of a Silvia shot is a rising temperature profile after 15-20 seconds (measured at the puck using a Scace device). Like the initial spike, I don't believe this rising profile serves any useful purpose. I believe it is better to eliminate this late-shot rise to the maximum extent possible. So considering the natural tendency of a single boiler shot to have a rising shot profile anyway, adding more heat to the mix (by using the steam switch) does not sound like a step in the right direction to me.

From the temperature standpoint, with a Silvia you will get the most level profile by cracking the steam valve for a few seconds immediately before pulling a shot, and by keeping the heating element turned off until the shot is complete.

The idea that the quickly dropping temperature at the top of the boiler translates into a dropping temperature in the water hitting the coffee makes sense, but it is wrong. In fact, the temperature at the coffee will continue to rise slightly even after the temperature sensed at the top of the boiler has already dropped 10F to 20F during a shot.

I have observed and measured this literally hundreds of times in the course of designing, testing, and building PID systems. The graph below, chosen randomly from testing done this week, illustrates typical behavior of the temperatures at the top of the boiler, and in the brew channel (no steam wand bleeding was done).

Jim

Very, very interesting and useful information!

Jim, that's an informative graph. I'm a bit surprised that during the shot that water existing the boiler doesn't fall in temperature due to the influx of cold reservoir water. But its certainly good news what you show.

On a related note, do most pump machines push water in the grouphead by also pushing (cold) reservoir water into the brew boiler? Seems fundamentally like it'd affect the shot temp.