Quick Mill Verona Modifications
So I’ve been off work for the last couple of days with a bad case of Man-Flu (which is extremely rare for me). Due to lack of sleep and aching body this has rendered me exactly useless in the morning but clearing up slightly in the afternoon. This combined with the Mrs being at work has left me with some significant and long overdue “tinkering time”. So what have I been up to?
Since first using my Verona I have always thought that the flow rate from the group looked a little quick when compared to other set-ups/videos etc.. After some serious googling I found some info (sorry I don’t have the sources to hand now) none of this is fact, just opinion and speculation but there was enough info to make me want to test the theory.
1. Water debit should ideally be around 75ml
2. WBC coffee machines have smaller flow restrictors/lower water debit than a standard e61 group
3. Higher water debit can increase the risk of channelling and other nastiness
4. Higher water debit can increase fines migration as the water hits the puck harder, resulting in a very slow start to the shot and a very quick finish (I might have come up with this one)
I could probably go on but you get the idea.
So, I ordered a bunch of E61 replacement jets from the states and waited, and waited, and waited, they arrived after a month thanks to the highly efficient C&E department, where they sat for two weeks. The new jets are 0.5mm as opposed to the standard E61 which is around 1mm so it’s quite a change. I picked up 5 as I thought I may want to bore out a couple to different diameters for testing (it turns at that at this stage this may not have been necessary)
So a couple of nights ago I finally decided to give the new jets a go. Fitting them was easy, remove the large nut from the top of the group and the metal filter that sits inside it. Once they are out the little nut you can see is the jet. A few seconds with a small socket and the old jet was out. Fitting the new jet was slightly trickier, I used the Mrs (apparently very expensive) tweezers to position the new jet and to make the first turn to ensure no thread crossing. A few more turns with the socket and after replacing the filter screen with nut and it was good to go.
Water debit is the amount of water that flows from the group in 10 seconds. So how did the new jet affect the water debit?
Old Jet – 113ml
New Jet – 76ml
Quite a difference, I was worried that the 0.5mm jet was going to be far too small (especially after seeing it for the first time) but I went with it and it turns out that it’s pretty much bang on what the Internet says is correct.
Since fitting it I’ve certainly noticed that I’m getting better extractions, they flow in a more controlled way and they look more pleasing on the eye. Of course all of this is useless if they taste like crap!
Well I’m happy to report that there have been a number of improvements in the cup too. Firstly the mouthfeel is better, thicker, smoother and I like that. I’m also guessing that I’m now getting a higher extraction yield as I’m getting more dark red fruits coming through and the acidity is much more balanced with the rest of the shot.
So far there are no downsides that I can come up with and I’m confident that I’m going to stick with it exactly how it is at 0.5mm.
If people are interested then I could do a video of the before/after flow rates.
Right is old jet, left is new
I’ve always wanted to experiment with brew pressure, partly due to the high flow rates mentioned above and partly due to reading up on various machines that use pressure profiling (Slayer etc.) or have it inherent in the design (Londinium L1 etc..).
I first started with some pre-infusion tests using boiler pressure only as I’m not plumbed in. It’s worth saying that all of these tests were done before I swapped the jet. I was finding that around 4-5 seconds of holding the lever in the middle position gave good results with my setup. It helped even out the flow rate of the extraction and brought out some of the flavours that I’d been missing. I did find that the results were quite variable and it wasn’t an exact science so decided to knock that on the head for now. I think that maybe if you were plumbed in on a consistent line pressure then the middle position would be much more useful.
In a lame attempt to try and emulate a slayer pressure profile I found on their website I messed with things like kicking the pump in and out at the start for the shot to try and achieve lower pressures before hitting the puck full on. Again it was so hard to maintain a consistent technique (not to mentioned a massive ballache) that I decided to give up on this as well.
Something that I could affect and maintain was the static brew pressure so I grabbed a screwdriver and started playing with the OPV. The results were not that interesting and I tried 6bar (after watching an L1 pressure ramp video) and 8bar (after watching a different L1 pressure ramp video). The results were a little surprising. At 8bar things were good and it improved both flavour and mouthfeel, very nice indeed. At 6bar the extraction hardly worked at all there were dead spots everywhere and it seemed to be blonding right from the start. I stuck it back to 8bar and reaped the rewards.
After fitting the 0.5mm jet I decided to try 8bar vs 9bar just because. I’m glad that I did because with the new jet and the OPV set to 9bar the espresso is just awesome. Today with these settings and some challenging beans, I can say that I’ve had some of the best shots that I’ve ever personally made and I’m really happy with my setup right now.
Whilst I had the screwdrivers out and following a conversation with a fellow Verona owner I decided to check the cam out and give it some love. I followed a video on YouTube (YouTube Link) which showed step by step how to dismantle this part of the group and made the process painless. When I got to the cam I was surprised at how much it had worn down and I gave that parts a good lube as per the video and put it back together. Based on how much my Verona has worn down in less than a year and how easy it is, I would highly recommend that anyone with an E61 does this every few months or after they perform a chemical backflush, I certainly will be from now on!
There are a couple of parts on the Verona that can rattle when the pump is running. It’s been annoying me for ages so I decided to fix it. This one was simple. The parts in question were the drip tray lid and the top case cover of the machine. The fix was to take some small pieces of Blu-Tack and re-enforce the pre-existing foam padding. The Blu-Tack gives extra padding and also keeps the parts from moving so that they never come into contact with any other parts. A simple but easy fix
Some will no doubt think why mess with all of this stuff. But I love it! The way I see it is that the ‘rules’ for espresso were created a while back and were designed around darker roasted beans which may not be as relevant with today’s lighter roasted speciality coffee. I do this because I want to get the best espresso I can with the equipment that I have and it interests me greatly.
Thanks for reading my ramblings and I’m sure that most of the information in this post is old hat to most on this forum, but maybe it will be of use to some.