Tal but raising pressure, increases the boiling temperature!
Even ecm “ cannae change the laws of physics” no more than the Clinton’s can!!
(P1V1)/T1 = (P2V2)/T2 when i was at school!!
At 2 bars boiling point is 120 approx depending on tds(!) but we wont go there!!
So its not boiling inside the brew water heater as that’s going to be circa 110
But when it reaches the other side of the valve it’s no longer at 2 bars
Hence the violent exit of water which can easily be seen when its from the bottom of the steam boiler running at 130 and using your hot water valve on a machine where hot water is from the steam boiler.
Theres no steam in the bottom of that boiler. Fact.
But there is at the water spigot as the water hits atmospheric pressure and has to contend with nearly going through a phase change as its steam if it manages ro still be above 100 C as its forced to quickly and therefore violently cool and hit atmospheric pressure almost instantly.
Now, that water you measure at the portafilter to be 97 is NOT 97 in the brew heater (nearer 110?), as it has to travel to the outside world and I’m discounting heated group which would help it stay above the group temperature, so still not boiling Until it reaches the other side of the valve. But you don’t see it until it gets to 97 as it travels through the system
So id suggest you are looking at the effect of this happening at the internal valve and it pulses through the system. Giving the effect of happening at the pf or spout. Rarely seen id suggest as its not as violent as getting hot water from the steam boiler
And for you to see what is most likely “fog” or condensation around the coffee machine you dont need steam for that . And remember you do see it far more in winter without the central heating on and the dehumidifier off ( because the bucket is full again due to the amount if moisture in the air ) than you do in summer.
@MuddyOne
As for measuring accurately, its difficult in a home setting with readily affordable equipment.
I don’t do it often enough to purchase a more accepted device so i stick electricians tape in the bottom of my portafilter leaving a hand full of holes exposed.
Use a spouted portafilter as this WILL squirt with a bottomless
Bend the thermocouple wire nicely around the side of the pf so it can easily be fitted.
Use a silicone head gasket so it seals completely
And measure the flowing water.
This gives a very slight flow through the pf so you get an accurate measure of the flowing water which would be far too much and inaccurate in a standard untaped basket as flow would be massive and the system wouldn’t keep an accurate temperature.
With a blind filter theres no flow so you just see the temp of the initial water that made it to the blind basket so likely marginally cooler than the true reading you are trying to measure.
ALSO
Remember to calibrate your thermometer with the thermocouple just under the water with a BOILING kettle. Not boiled, boiling.