Temperature surfing and pulling second shot on La Pavoni pre-Millenium

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twisterlove
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Joined: Jun 18, 2016, 8:45 pm

Postby twisterlove » Jul 15, 2016, 11:58 am

Folks,

I got a la Pavoni pre millena recently and it does not have thermo or pressure gauge to check the pressure.

I managed to get nice shots on it. However, I burn my shots from time to time with over heated water. I do not know how to always surf temperature the right way. The way I do it is:
once the safety valve ( I am not sure if that is the right name ) starts releasing steam, I turn the second switch (the white one) to I; heat group head and basket by releasing some hot water; then loading the basket with coffee and tamping it; I release some steam through the milk-steaming valve just before pulling the shot; and finally I pull a shot.

Any detailed advice for better technique?

Another problem is the second shot. If I have a friend and I need to pull more than one shot, I either get a burned shot, or if I do temp-surfing, then I end up with small amount of water after lifting the lever up for pulling the shot.

Any advice here, too?

Thanks.

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rpavlis
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Joined: Jan 08, 2012, 3:26 pm

Postby rpavlis » Jul 15, 2016, 2:25 pm

You really do not "burn" shots when the water temperature is too high. Although people commonly refer to the espresso making process as "extraction" it is not a simple extraction, rather it is essentially a chromatography in which compounds in the coffee migrate by going into solution, then reabsorbing, and repeating the process as they go through the coffee puck. Ones that migrate fast get to the bottom practically with the first water to come through, others spend more time absorbed and move slowly. Too hot water makes everything move so fast that all the nasty tasting stuff comes out during the shot.

Your machine appears to be a second generation La Pavoni two switch model, the one switch models with pressurestats were phased in over many years through the 1990s. You do NOT need to bleed the models with two switches through the steam valve, but you most certainly do need to do so with the one switch pressurestat models.

You might consider the purchase of an infrared thermometer, they seem to cost about $US12 these days. If you have a plated model you can stick pieces of tape onto the machine on places you want to read temperatures. If you have a polymer coated brass machine you can just aim the thermometer at points and get the temperature there.

Be sure the machine is filled with water. Turn both switches on. When the thing starts to hiss loudly, put a ramekin or other suitably sized bowl under the group and slowly raise the group handle until a bit of water is released. Lower it slowly. Repeat the process. This should clear almost all of the air from the space above the piston in the group so that heat transfer can occur. As soon as this bleeding process has been completed turn off the high wattage element. The group will heat very quickly. If too cool you will get a spongy low volume sour shot. If too hot you will get an intensely bitter shot. If the lower part of the group be near about 90C you will probably do best.

When making the shot you might set the cup and portafilter to the right of the machine. Raise the handle until a few whiffs of steam and a bit of water are released, and lower it just a bit to stop the steam and water. Attach the portafilter, put the cup under it, and raise the handle all the way. You might want to preinfuse by bringing the handle down just enough so some espresso emerges, then recock it and make the full pull.

Remember--too cold-sour, low volume, spongy pull. Too hot-bitter.

Using a deeper basket like the ones from a Micro Casa a Leva(with larger shot mass like 16-17 grams) may reduce bitterness because the puck will be thicker and the compounds will have to travel farther to emerge from the bottom.

It takes some experimenting to develop technique for these machines!

twisterlove
Posts: 26
Joined: Jun 18, 2016, 8:45 pm

Postby twisterlove » Jul 16, 2016, 1:59 am

Thanks.

I have a food thermo with a steel stick. I just used it to measure the heat on the outside surface: when the the valve starts hissing, it barely reaches 200 f; when I release steam to the point when hissing almost stops, it reads around ~170 f. I am not sure if my thermo is accurate, but I thought at boiling temp it will read >=210 f. Is it normal to read less temp than the actual water temp when using a thermo?

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drgary
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Postby drgary » Jul 16, 2016, 10:48 am

When I had a two-switch, second generation La Pavoni, I was able to get control of it for consistent shots, back to back. Here's the thread where I documented that:

Reaching the Zen Zone with a Two Switch La Pavoni

Robert's method of using an infra-red thermometer works and doesn't require installation. I like keeping my hands free by adding a group thermometer. Here's the thread I started on that, showing various approaches that evolved. What you've just described makes measurement a bit difficult because the steel sheath is still on your thermometer. You want good contact between the probe and the group. I accomplished that by putting a larger rubber o-ring on the outside of the group bell and removing the probe tip from inside the sheath. Take care with that because you can easily destroy your food thermometer if you break those thin wires.

Adding Thermometry to a La Pavoni Europiccola
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

twisterlove
Posts: 26
Joined: Jun 18, 2016, 8:45 pm

Postby twisterlove » Jul 16, 2016, 10:12 pm

I think I need some time to experiment with your suggestions. I think I will update here in about a week. Wish me luck :)

twisterlove
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Joined: Jun 18, 2016, 8:45 pm

Postby twisterlove » Jul 17, 2016, 10:33 pm

I bought a taylor digital thermometer. I attached it using metal tape (I read some of the threads you guys suggested.) It reads 109 c when it starts hissing. The temp does not get down fast. I released some steam and water, but more than the usual I do; the degree dropped to 102 c. I pulled the shot, and it came cold.

I used my other kitchen thermo, and found the temp to be much less than that, 72 c. I think the new thermo is not accurate; but the differnce is huge between the two. What to do?

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drgary
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Postby drgary » Jul 17, 2016, 11:11 pm

Dial in to either one by taste. A group thermometer is indicative. Also to test accuracy dip the tip of either in boiling water.
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

twisterlove
Posts: 26
Joined: Jun 18, 2016, 8:45 pm

Postby twisterlove » Jul 18, 2016, 8:34 pm

I rearranged the thermos and interchanged their positions. I positioned them closer to the group than to boiler. This time the temp difference between them is about 4~5 degrees.

And it worked :D After I released water and steam, I waited till the temp reached around 93 c on one of them and pulled a nice shot! I will keep both of thermos attached; I think it assures semi-correct readings: if the difference is high, I know something is wrong.

Thanks folks.

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Calendar
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Joined: Aug 05, 2012, 1:52 pm

Postby Calendar » Aug 09, 2016, 8:05 pm

rpavlis wrote:Using a deeper basket like the ones from a Micro Casa a Leva(with larger shot mass like 16-17 grams) may reduce bitterness because the puck will be thicker and the compounds will have to travel farther to emerge from the bottom.

It takes some experimenting to develop technique for these machines!


I have a couple of double 49mm baskets but I don't know if they are Pavoni baskets or the deeper Micro Casa a Leva ones. They measure 25mm rim to the bottom on the outside.

 
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