2000 ml flask. temp check.

good question, but i'm not sure it matters. could be wrong too.
are you altering the starter temp before pitching? getting your wort to the desired temp is important, i personally pitch the yeast at ambient temp.

so your starter will be pretty close to ambient temp. you could set a glass next to the flask with 1L of water and measure the temp of the water. a non-contact laser gun will work. yes, they measure surface and not liquid but if you shake the starter a bit it will give you a very close reading. thats my idea anyway.

 

It's definitely not scientific, but I just wait until the flask is no longer warm to the touch. A little easier than a non-contact laser gun, although that sounds like an awesome gadget.

 

ah, you are looking to see after you boil your DME, not after you have developed the starter with yeast for pitching into wort. seems obvious now...

pyrex will go from hot to cold. not boiling to freezing though.
i put the hot flask into a pot and turn the faucet on. the pot fills with water and drains away the heat from the flask. adjust the temp of the water from your faucet and let it run for a while. the two liquids will eventually equilibrate. swirl the starter to speed things up. you can buy weighted ring to place on the flask to keep it from floating, otherwise you have to hold it steady.

 

Are you boiling in the flask? If so, it may end in tragedy (shattered flask) one of these days. I know some will jump in and say "My flask is Pyrex, and I have boiled 'X' starters in my flask and it hasn't broken." Those would be the people who haven't had their flask break yet.

I boil in a pot, so it's easy to measure the temp. I then pour into the flask through a sanitized funnel.

 

I set the flask on the thermometer and set both on a towel. Seems to work.

 

You might want to get a lab thermometer. The one I have is plenty long enough to reach down into the flask. They's only about $5. If you don't have one and have to move forward with your starter, I would follow mporter's advice and just make sure it's cool to the touch. Try to err on the cool side if you're not sure.

 

yeah, pyrex is tough stuff, but not bullet proof. i broke my first flask going from boiling to cold. the thin stuff we get is made in India and not as good as labware. but its also a hell of alot cheaper.

i wouldn't put a boiling flask into cold water, but i have boiled X starters in my flask and it hasnt broken.
you cursed it. thanks.

 

As long as your starter wort is cool to the touch/ cooler than blood you will be fine to throw your yeast in. Starter temp is not nearly as important as a correct main batch temp along with consistent fermentation temp.

 

+1. Since you will be decanting most if the liquid you will be discarding the majority of any off flavors developed. Same reason you can use a starter with lager yeast with minimal problems.