# Steam knob pre-infusion



## Daniel R (Feb 2, 2020)

Hi,

I just came across an interesting method for pre-infusion. The video is about a Gaggia Classic Pro, but it should work the same way for the Silvia.






My steps:



Put a container under the steam wand (I use the milk jug)


Open the steam knob fully


Flip the brew switch to start pre-infusion


After 5-10 sec of pre-infusion, gradually close the steam knob


During the pre-infusion water should flow to the puck with no pressure. After about 5 sec, the pump noice changes. Probably when the puck starts creating resistance. That's when I start closing the steam knob. Also, I have never gotten any first drip, even when doing a longer (15-20 sec) pre-infusion.

Have anyone else tried this methon? I think it's improves shoot, but have not done any real tests comparing with and without pre-infusion. Another interesting test could be to stop brewing after the pre-infusion and see how wet the puck is.

Daniel


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## newdent (Feb 20, 2021)

I've also seen this discussed, if it works, it would make more sense than the more widely seen silvia 'pre-infusion' of brewing for a period of time, stopping for a bit and then beginning to brew again as pre-infusion is meant to be done at a lower pressure AND stopping and starting the shot can't be a good idea as it must disrupt the puck.

If the silvia had a pressure gauge, it would be easier to experiment and at least attempt to control in a repeatable way. Maybe someone who has added a pressure gauge to their silvia could test and comment?


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## newdent (Feb 20, 2021)

This person has a gauge and it says they're using mecoffee to control the pump on a pressure profile. I didn't think this was possible but maybe it is? The pump certainly sounds a bit ropey unless that's something else vibrating... Shame they filmed the extraction and not the gauge, looked like it shot up to at least 4 bar initially though, when they said it was meant to start at 25%.


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## newdent (Feb 20, 2021)

Oh wait, same person has a better video of a profiled shot and it certainly seems to hold at the pressure setpoints...


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## Stox (Jul 19, 2020)

I sometimes do this with my Gaggia Classic. One thing to be aware of is that with the steam valve is open and the pump running you are pushing more cold water into the rather small boiler than would otherwise be the case with a normal shot. If you don't close the steam valve quickly - or arrange to start from a higher temperature - you will lower the temperature of the resulting shot substantially.


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## newdent (Feb 20, 2021)

Stox said:


> I sometimes do this with my Gaggia Classic. One thing to be aware of is that with the steam valve is open and the pump running you are pushing more cold water into the rather small boiler than would otherwise be the case with a normal shot. If you don't close the steam valve quickly - or arrange to start from a higher temperature - you will lower the temperature of the resulting shot substantially.


 Good point, probably not much use in controlling the pressure if the water temp is all over the place!


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