Boiling question for propane burners

For those of you out there who have used propane burners, once you reach boiling do you have to keep the propane screaming or can you manage it down and up to maintain?
Secondly, from the “I don’t have a science degree” file, can I expect my SS kettle do be the same temp as the wort inside? The reason I ask is that I want to be well prepared to avoid melting my plastic tub where the kettle will cool (Polypropylene, melts around 230).

Thanks everyone.

Once a boil is achieved you can feather the flame back to maintain a rolling but not rollicking boil. I think it’s safe to assume that the bottom of the pot is considerably hotter than 212 degrees when the flame is on but I would guess (An I too am not one of those science guys) that it will drop pretty quickly after flame out. as long as the water is already in the tub when you lower the kettle in it won’t melt… I think…

10-15% evaporation is plenty for what we’re looking to accomplish in the boil. Any more than that and you’re just wasting propane.

As far as temperatures, water/wort is an excellent conductor. The kettle should be at the same temperature as the wort within a few seconds after you stop applying heat. You might want to leave it out of the tub for a minute or so to play it safe.

I was going to add that, at least with my kettle, you can sort of tell when the temp of the kettle has reached equilibrium with the wort after flame out when the wort actually stops boiling. for me that takes maybe 30 seconds or so. so yeah a minute should be safe.

Measuring evaporation would be tough for me to judge. Are you saying its doesn’t need to be an explosive boil the whole time?

I’ll just place my palm on the pot.

for sure not explosive. and you will learn your systems range of evaporation. think boiling pasta.

A steady boil is plenty.  If you leave the gas on high you will quickly get introduced to what is called a boil over and have nice mess to clean up.  The wort is sugar loaded water that will stick/burn on every surface it runs out on to.  I had one happen last Saturday, in fact.  I was reading this forum instead of watching my brew.  luckily I have a power washer so clean up wasn’t too much trouble.

One thing to remember is the pot will continue to absorb heat after you turn off the burner.  My stand will have some spots that are red hot after I turn off the gas.  That heat has to go somewhere so a lot of it gets  absorbed into your brew kettle.  Take the kettle off the burner and set it on the ground/patio/garage floor/deck(with a towel or something under it) and let it cool a bit there before you put in the plastic container.

Paul

Just to clarify, would more evap. simply make less beer or is there another risk involved (taste, etc.) with increased evap. during boil? Thanks!

less stronger beer. but if you hop a beer expecting say 4.5% abv and you end up with 6% abv the beer will taste quite different. Not as bitter and potentially unbalanced.

EDIT TO ADD
I sometimes intentionally do a very long boil with lots of evaporation on strong beers like barley wines because it will develop different flavours do to the longer boil. It is refered to as kettle carmelization although it is not really carmelization. The wort will get darker and sweeter and it can produce more raisiny dark fruit flavours.

Recipe should be calculated for final five gallons. You can make a measure stick and check occasionally. When you get to about 5.5 just partial lid it.

But remember you are in Florida. You may end up with more than you started with due to humidity lol

“Friends don’t let friends drink bad beer”

I would put some sort of spacer on the bottom of the tub to keep the pot off the bottom - partly to avoid melting the plastic, but mostly so that the bottom of the pot is in contact with cooling water.  Cooling speed will be faster with more surface area.