Gaggia Classic - Too much pressure!

by **JimM** on Thu Apr 14, 2011 3:06 pm

After a friend at work tried some coffee I ground for him and it took 3 minutes to extract a shot it wasn't hard to work out something was wrong with one of the machines :lol:

I fitted the blind and ran the pump for 30 seconds, the OPV doesn't open during the 30 seconds and I get 13ml when its shut off so it must be way over pressure.

What affect does this much pressure have on taste?

by HB on Thu Apr 14, 2011 3:23 pm

First of all, see I still don't get it: Why adjust the OPV? for background information. To answer your last question, telltale signs of excessive brew pressure are bitterness and dark crema / oil droplets, i.e., overextraction. If the puck channels, then add the symptoms of underextraction, i.e., dull flavor, sourness, light crema color.

by **JimM** on Thu Apr 14, 2011 3:33 pm

My results are starting to make more sense.

by **JimM** on Thu Apr 14, 2011 5:43 pm

Well like an idiot I was measuring from the drip tray pipe.

Now that I've done it correctly with a bit of tweaking to the OPV I'm getting 100ml in 30 seconds through the return pipe.

Not sure how much it was over from the factory as when I noticed my blunder I'd already got the socket on the OPV so just carried on. It was definitely over pressure as I unwound it at least one turn. Will be interesting to see what the morning espresso is like.


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