Espresso Machine Maintainance: Group Head
One of the most important thing in espresso making is group head maintainance. Afterall, the group head is the site of the most significant action where by coffee grind are extracted by pressurized water. Thus it is very important to keep the group head of the espresso machine alway clean. After a shot is made, group head should be flushed clean, gasket should be brushed and everything wiped down. Backflush with detergent should be performed at least two times per week.
With that said, another thing that usually go wrong with espresso machine is the group head gasket. The group head is an extremely hot place and rubber gasket material do not last very long here. It is recommended that group head gasket be changed every year and more often if nescessary. Once you see that when making a shot, you get water leak around the portafilter even if you try to wrench the portafilter into place then it definitely is time to change the gasket. If you ignore this and wait longer, the group head gasket will fossilize and become baked onto the group making it almost impossible to remove it. (as a side note, this did happened to the La Marzocco Linea that I was restoring before and it took me more than an hour to drill out the gasket, a real pain in the behind).
So last weekend, it was definitely time for me to change the group head gasket on my Nuova Simonelli Musica espresso machine. Here is a little peak at what the old gasket look like:
/files/u14133/hinh_sn_225.jpg" height="375" width="500" />
You can easily see the crackling in the gasket, and thus the reason why the group head was leaking. Also, in the background is the shower screen and the dispersion block. Looks pretty bad huh? Actually this is with frequent detergent backflushing! So it is a really good idea to take off the screen and the dispersion block and immerse in a hot solution of backflush detergent maybe once every month or so. As for the gasket, it was not too hard to remove. A thin flat head screw driver would work but in this case I used a dental pick which avoid damaging the finish of the group head. I then scrub the group head to remove any trapped coffee oil in the group head groove and put in the new gasket. Before putting on the dispersion screen and shower screen, I used a portafilter with the basket removed and engaged into the group head as to make sure that the group gasket is seated properly. Then the dispersion block and the screen goes back together and voila, it is done in less than five minute.
I was enjoying some really good espresso last weekend from the Nuova Simonelli as a result! Next up is descaling the machine as I think that it is time for it!