Microcimbali restoration - boiler anodic protection - Page 3

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#21: Post by maki »

interesting, you had to do 3 pulls to get coffee going into cup?
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#22: Post by XS750AU (original poster) »

Pulled a few more shots this morning. My attempts at Lattes, suck. I just cannot get the milk right.
Espresso shots are very good. Not getting as much crema as on the Expobar, but the shots are deeper, richer and smoother. Very happy with them.
I am still playing around with the recipe. I think I have to back off the tamping pressure as getting the pre-infusion required 2 lever strokes, which does not seem right? :?
I did insert a thermocouple in behind the sight glass cover.

The temperature does fluctuate a little. It peaks at 101C when the pressure valve pops. It then settles and drops to 97C and the pressure valve has sealed. This cycle appears to be consistent. I am using a light roast and the shots are not burnt, they are great.
My extraction is very slow and 2 lever strokes yielded a 31gr shot. So I needed 2.5 lever strokes to get a 40gr shot from an 18gr grind, time was over a minute. That is why I guess in need more work on the grind and tamp?? :?

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#23: Post by TomC »

I think you're on the right track. A more developed roast, lower dose, coarser grind should yield the classic Italian style shots that these were designed to produce. I wouldn't want to do a dozen rain dances in order to get an adequate volume or flavor result out of a lighter roast, on a device like this, I have better tools for those coffees.

A double pump sounds reasonable, it shouldn't require too many complex machinations. Again, slightly coarser grind, lower dose, more developed coffee or blend of coffees.

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#24: Post by XS750AU (original poster) »

I bought some Ethiopian Dark roasted beans from the local roaster this morning. I had a full schedule today, but managed to get one shot off. I had both elements on until 85C, then I turned off the 1000W element and let it coast into steady state with the 300W element. The thermocouple is not elegant, but it is very useful in getting to know the machine.
I cut the dose back to 16.5gr and move the grinder setting 2 notches finer from my Expobar datum. It took 1 stroke to pre-infuse, and then 2 full strokes to get a 34gr shot. Deep, rounded, smooth, chocolate, spice, nice shot.
So far I am happy with the results, apart from the first 2 or 3 shots when I was just establishing where the hell I was, I have not had a bad shot. Very impressed with the consistency.
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#25: Post by maki »

very nice! cant wait to get my machine in the post to start playing with it (hopefully it wont break my budget with repairs :roll: )
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#26: Post by XS750AU (original poster) »

Just to confirm, I am leaving water in the boiler so that the anode remains in the electrolytic circuit. The whole idea was to see if a magnesium anode would protect the aluminium boiler. In a month or 2 I will take the boiler off and inspect both the anode and the boiler. Hopefully the magnesium anode will show signs of being consumed.

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#27: Post by XS750AU (original poster) »

Time for an update.
I took the angle grinder and cut the bottom off the portafilter. Then a bit of a touch up with the flap disc.

Does make it easier to see what is going on with the extraction. This shot was not the best, but still very drinkable.
The crema it thick and consistent.

The most important check so far, was the condition of the anode. It has changed colour and the immersed surface does appear to have started to etch meaning it is loosing material into the solution (water). I am keeping water in the boiler to maintain the electrolytic circuit, and hopefully protecting the aluminium boiler, only time will prove or disprove this theory.
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#28: Post by RomanSteff »

Hello dear colleagues, owners of micro chimbalis. I have Liberty since 2010, and just like you are concerned about the health of an aluminum boiler. In most cases, pitting corrosion occurs in the lower part where the heating element is located. Perhaps tinning the problem areas as a protective measure? After all, tinning is used for pots, teapots, samovars, etc. Apparently, tin is much safer than zinc, magnesium and aluminum when it enters the human digestive system.

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#29: Post by XS750AU (original poster) »

Hi Roman
Thank you for your input. Did a little bit of research on your idea, and it appears that the actual process of applying the tin coating is not so easy. Definitely much more difficult than applying tin to steel or copper. From what I could find it would require a multilayer electroplating system.

" You cannot electroplate directly onto aluminum because it is so active that it forms a passive skin instantly. The normal procedure is to immersion plate zinc onto the aluminum via a zincating bath, and then proceed with alkaline copper and tin plating, or alkaline electroless nickel and tin plating."

Appears to be complicated.
Only time will tell if the magnesium anode will work effectively, I am getting some sediment in the bottom of the boiler, which may be from previous contamination or from a reaction with the magnesium anode. The experiment continues!
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#30: Post by maki »

have a question. how did you took apart the boiler from the machine?
i see a small screw where is a 220v logo but the boiler wouldn't come apart...
am i missing something here?
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