So final post with a summary of TIME & temperature…
Would recommend you don’t fiddle with the temperature, (65.5c) EVEN IF your coffee container is 1/3 out of the water, let it heat up, take a few internal & external temp readings when you stir grounds in with a stainless steel chopstick… the temperature differential will likely be 5c …so put your coffee in the sous vide container from the word go to acclimatise.
Side note: If using a laser dot temp reader, remember it measures the surface of the class not the liquid inside, OR if you open the jar, red dot point at the top …you are measuring the top temp not throughout the jar, it is a guide only
Basically, if making batch (why wouldn’t you)!? the 2 hour time needs consideration due to inserting a big old jar of COLD, fresh poured water (2 litres is more than the atypical capacity of a UK / EU kettle) into a pre-heated bath so maybe allow 1 hour warm up time +2 hrs brew time, up to you, but something to consider if honing timing versus elusive flavours !?? (not enough for me to concern myself with as it has always been smooth & non acidic / lacking in harsh notes commonly associated with hot coffee as the familial comparison.
Secondly, (& bear in mind I used the same proportions & same coffee type each time,… there was negligible difference in taste of the milk & creamed up cold brew product be it 2 hours cooking time or through to 12 (overnight) so don’t leave sleep too much the basic results were nigh on the same (save some time & electrical energy)
Lastly, again I tried giving a full to the brim stopper cap bottle 24 hrs rest time in the fridge to reduce harsh edges … I didn’t need to whether it was taken once filtered & briefly chilled, or rested sealed for 24 hours, no discernible difference in flavour, acidity etc…
So make of that what you will, my coffee was Colombian Costco Kirkland, pre-ground, cannister that I suddenly remembered had been open for months (really)
Every coffee has different signature notes, & flavour decay potential, so don’t crucify me if you find different, I used the same measurements be it coffee, water, container, condensed milk, evaporated milk, semi skimmed, full fat milk pouring cream, …you get the point.
2 hours will suffice, thereafter if you get caught up in other work, it is going into flavour stasis for at least 12 hours.
If you wish to emulate store bought cold brew then you need either the following…
A dollop or more of whipping cream (if to be drunk on the spot) this is on top of whichever milk you use as standard…
Or for longer term storage in a well chilled fridge (I use a sigg dual wall copper lined flask …lid pref yours of course, several available) & the mix of semi skimmed, condensed, & evap milk, …the condensed gives it “mouth feel” thickness & sweetness associated with a pay through the nose shop bought) …likely you can miss out the evap, but NOT the condensed, it is what makes it familial after all.
Please, don’t be lazy, pour your condensed milk into a sealed non metallic container to keep it in tip top condition, it will add significant cost to the make up of a couple of litres but likely a standard can will suffice just about for the amount I made each time, 397g of carnation or whatever brand sells cheapest if you don’t make it yourself that is
Brands like carnation do caramel cans too, this is NOT a substitute for condensed milk, in fact it doesn’t work very well in anything other than a pour over visual enhancement, due to its gloopiness compared to the stir-ability of condensed milk, & a lot of that caramel flavour is lost to the coffee, so if slurped off the top / edge of the glass, fine, but wasted as a condensed milk replacement I promise you (& considerably more expensive to produce / buy)