Announcement

Collapse
No announcement yet.

Headspace, crema bubbles and the cooling flush.

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Headspace, crema bubbles and the cooling flush.

    Hi all

    I have been experimenting a lot today with my new Galatea (no one has commented on my take on Dali in the older topic, oh well). Im trying to get my grind and tamp right as it needs to change from my Silvia. The shots are good from the Galatea but could be better. I have tried today differing grinds with the Weis technique using a needle, with and without a mid-tamp, and Anyhow I have some pics here I would like advice on.
    - Bean is Ethiopian Harrah, nunu nicely made me a kg so I have lots to play with. 5 days rest.
    - Basket is a double one, 24 mm deep.
    - Grinder is a Rocky, doserless. It does clump a bit.
    - Tamping method. I generally fill with wiggling of the PF against the prongs to distribute. A light tap on bench then brush off flat with a chopstick. Then tamp with Espro tamper.

    Headspace: Some sites advocate to have some headspace above the coffee, i.e. a gap between the coffee and the screen. With my Silvia I always filled till I got the small impression of the screw in the puck - absolutely no headspace. With the Galatea one gets no impression but I would have thought one would fill till it just touched the screen. I tried a few with some headspace but I think one ends up just underdosing. Pic 1 shows the puck that had headspace. It looks like flowing water has patterned the surface. The coffee from this was just acceptable. Pic 2 shows a puck with no headspace. Question: for an E61 machine should one have headspace?

    Crema Bubbles: In some of my shots I get largish bubbles in the crema, Pic 3. Other shots have smoother appearance to the crema and less bubbles, Pic 4. Shots with bubbles in the crema also tend to have a darker crema. Question: Is the darker crema and bubbles indicative of too high a temperature of extraction?

    Flushing: I have seen the videos of the HX water dance and the cooling flush. It shows spitting of hot water which then settles down indicating the temp is now stable and correct for a shot. With my Galatea if its been on for a while and I open the brew handle I get steam from the water coming out the brew head but no spitting like the videos. I can let it run but there is really no change to the water exiting the group head. I therefore just flush about 50mL to 1/2 fill the espresso cups just before a shot. Question: Does anyone with a Galatea see really hot water spitting like the videos show.

    Mike





  • #2
    Re: Headspace, crema bubbles and the cooling flush

    Regarding Flushing I get the same as you

    Regarding the head space I leave aprox 1mm gap to the screen to allow for expanssion it gives me great results

    Yes I did like the take on Dali

    KK

    Comment


    • #3
      Re: Headspace, crema bubbles and the cooling flush

      With cooling flushes, machines like these tend to have very stable temperature. So unless the machine is idling for the last 2hours+ youre not going to need a 200ml flush. Even after a 2 hour idle time, i only flush about 100-150mls of water from my domobar.

      With dosing on the domobar(dont know if it transfer to the galatea), if you dose up till there is no headspace and the puck scrapes against the shower screen, it will crack the edges of the puck and youll get heavy channeling.

      So you want a dose which touches the screen when your PF is fully locked. If it touches even before you lock it in, it will push the puck to the left and the right will channel.

      Down dosing will work, but youll need a finer grind because ur getting less resistance with the lower dose.

      With crema appearance, I reckon its a lot to do with the coffee youre using and the freshness. Not so much the extraction. However, an under extracted shot will have very pale crema and an over extracted shot will have a darker crema but you should be able these by looking at the pour.

      Larger bubbles are quite common if your beans are VERY fresh
      Darker crema and flecking is also more common in blends and darker roasts.

      I generally start drinking everything 7 days+

      Hope that helps!

      Correct me if im wrong Just my 2cents

      Gav

      Comment


      • #4
        Re: Headspace, crema bubbles and the cooling flush

        Hi Gav

        Ah so idling for 30 mins means its temp is prob still fine. Lots of sites say "idling for a while" but dont say how long a "while" is. I havent done big flushes of 200 mL but just 50 mL before each pour.

        Maybe Im overfilling my baskets. OK so I do need some headspace to stop any movement of the coffee when locking in. I was very used to the small screw on the Silvia :-) I will fill & tamp and lock in and then remove the PF to see at what fill level the basket touches.

        You may be right about the edges of the puck cracking. The pour starts out quite nice after about 6 seconds delay, its nice mouse tails and viscous but only for about 4 seconds, then the flow is very runny. Not blond but its lost much of its deep red/brown.

        I have been getting the larger bubbles often in most of my own roasts which have been from 7 to 10 days old so Im suspecting my technique.

        Mike

        Comment


        • #5
          Re: Headspace, crema bubbles and the cooling flush

          Hi all

          Given what Gav mentioned I went and filled the basket with settled, but not tamped coffee and loaded it into the group head. Then removed it. If there was no marks from the screen I added more, settled it by tapping and loaded again. Once I had a faint mark I tamped and reloaded. When removed there as expected was no mark.

          The weight of coffee for this is 14-15 gms. The scales alternative between 14 and 15 as they are only to 1 gm resolution. It just so happens that the Espro tamper for this fill is just flush with the top of the basket. The Espro thickness is 11 mm so this places the tamped coffee surface 11 mm below the basket surface. This is deeper than what I have been using.

          Ill try tomorrow to use this level and re-adjust the grind down to get my 25mL in 25s rate and see how the pour looks.

          Mike

          Comment


          • #6
            Re: Headspace, crema bubbles and the cooling flush

            Dont know how much the galatea basket takes but 18/19 grams touches the screen, 20 is still good but a little over 20, 21 grams and it scrapes the screen.

            Comment


            • #7
              Re: Headspace, crema bubbles and the cooling flush

              Hi
              The basket Im using is 24mm deep. Whats yours in depth?
              Mike

              Comment


              • #8
                Re: Headspace, crema bubbles and the cooling flush

                Cant really get an accurate measure but its about 23mm.

                Comment


                • #9
                  Re: Headspace, crema bubbles and the cooling flush

                  Hi

                  Actually I can get 18 gm in. The 14 gm was when it just touched untamped. Then tamped of course it was clear. I weighed 18 gm into the basket then tamped and it just by a smidgin touches the screen. A few grains were disturbed so tomorrow Ill try for an 18 gm load.

                  Mike

                  Comment


                  • #10
                    Re: Headspace, crema bubbles and the cooling flush

                    Originally posted by speleomike link=1214654455/0#0 date=1214654452
                    Hi all

                    I have been experimenting a lot today with my new Galatea (no one has commented on my take on Dali in the older topic, oh well).  Im trying to get my grind and tamp right as it needs to change from my Silvia. The shots are good from the Galatea but could be better.  I have tried today differing grinds with the Weis technique using a needle, with and without a mid-tamp, and   Anyhow I have some pics here I would like advice on.
                    - Bean is Ethiopian Harrah, nunu nicely made me a kg so I have lots to play with. 5 days rest.
                    - Basket is a double one, 24 mm deep.
                    - Grinder is a Rocky, doserless. It does clump a bit.
                    - Tamping method. I generally fill with wiggling of the PF against the prongs to distribute. A light tap on bench then brush off flat with a chopstick. Then tamp with Espro tamper.

                    Headspace: Some sites advocate to have some headspace above the coffee, i.e. a gap between the coffee and the screen.  With my Silvia I always filled till I got the small impression of the screw in the puck - absolutely no headspace.  With the Galatea one gets no impression but I would have thought one would fill till it just touched the screen.  I tried a few with some headspace but I think one ends up just underdosing.  Pic 1 shows the puck that had headspace. It looks like flowing water has patterned the surface.  The coffee from this was just acceptable. Pic 2 shows a puck with no headspace.  Question: for an E61 machine should one have headspace?

                    Crema Bubbles: In some of my shots I get largish bubbles in the crema, Pic 3.  Other shots have smoother appearance to the crema and less bubbles, Pic 4.  Shots with bubbles in the crema also tend to have a darker crema.  Question: Is the darker crema and bubbles indicative of too high a temperature of extraction?

                    Flushing: I have seen the videos of the HX water dance and the cooling flush. It shows spitting of hot water which then settles down indicating the temp is now stable and correct for a shot.  With my Galatea if its been on for a while and I open the brew handle I get steam from the water coming out the brew head but no spitting like the videos. I can let it run but there is really no change to the water exiting the group head. I therefore just flush about 50mL to 1/2 fill the espresso cups just before a shot.  Question: Does anyone with a Galatea see really hot water spitting like the videos show.

                    Mike



                    Your results would improve dramatically with a decent grinder. Keep the rocky for decaf and invest in a Mazzer Mini...

                    Good Luck

                    Comment


                    • #11
                      Re: Headspace, crema bubbles and the cooling flush

                      I am contemplating in getting a convex base tamper (U.S./1.5mm curve) to accommodate the shape of the head of the Galatea
                      It may be another tool in my Domus Barista Kit for fine tuning  :

                      KK

                      Comment


                      • #12
                        Re: Headspace, crema bubbles and the cooling flush

                        Hi Kosmo

                        Thats an interesting point. I have two tampers, a Tobys Estate (convex) and a Espro (flat). With the Silvia I used the convext tamper and with the Galtea I have been using my new Espro tamper:

                        Silvia screen is flat + convex tamper = most headspace in middle.
                        Galatea screen convex + flat tamper = most headspace at periphery.

                        The shape of the headspace then is completely different in the two cases; plano-convex vs. concave-plano. Im not sure if its significant or not.

                        Mike

                        Comment


                        • #13
                          Re: Headspace, crema bubbles and the cooling flush

                          Greg and I have differing opinions on this issue.... Greg preferring flat whereas I prefer Convex (on my machine at least).....

                          My La Cimbali M20 has a convex showerscreen.... and I dose so that the unextracted puck just touches the showescreen.....

                          If I use a flat based tamper there is a widening gap as you move towards the rim of the basket. When water hits the puck it expands..... in the centre there is no where for it to go.... and becomes denser.... near the periphery there is a space and the puck can expand.... remaining at a lower density.

                          As water will always take the path of less resistance..... more will flow through the puck near the edge and less near the centre..... so the puck near the edge can tend to be overextracted.

                          If you down dose so the puck is much lower than the showerscreen this wont apply.... or apply but to a far reduced amount (depending how much "gap" exists between the showerscreen and the surface of the puck).

                          So IMHO, best results should be obtained when the profile of the tamper matches the profile of the showerscreen...... But that is only an opinion based on my theory and experience (for what it is worth) :-/

                          Robin.

                          Comment


                          • #14
                            Re: Headspace, crema bubbles and the cooling flush

                            Yes Robin you put in words exactly what I was thinking
                            I have been tamping with the flat pamper leaving a gap of approximately 1mm or less for the reasons you give above

                            That’s why I was contemplating a convex tamper
                            My thinking was that it makes sense to match the shape of the puck to the shape of the filter head
                            Now I think I will get one
                            Robin will the American 1.5 mm curve be suitable for the Bezzera Group head

                            KK


                            Comment


                            • #15
                              Re: Headspace, crema bubbles and the cooling flush

                              KK,

                              The convex bases we supply (and I use) are 1.5mm convex. It works perfectly on my La Cimbali and other machines with a Convex showerscreen.

                              Whilst we dont sell a lot of these bases in Australia, they sell very well into Europe and the Americas..... and we have been receiving very good feedback from those who have purchased them (for use on a range of different machines).

                              Robin.

                              Comment

                              Working...
                              X