1st Berliner Weisse, a little help?

Beer Recipes
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Ok, I know, another BW thread, but since there are so many different variations, I just want some reassurance. I am down to one Crabtree BW and am not headed back to Co. anytime soon so I thought it is finally time to brew this up.
Planning on something along the lines of OG 1.035 or so FG 1.007ish, close to 50-50 wheat and Pilsner malt, and .5 oz of noble hops. Not really sure on the water to grain ratio as I plan to do the full sour mash for 48 hrs (cooler tun) and would like to be able to add small amounts of boiling water to the mash to heat it if needed. I also have a brew-pad that I am considering using to try and maintain the temp, not sure if it will even work with the cooler? Also, what is the best temp to mash in at? with this type of full sour mash should I mash in at the low end, say 149 or stay in the range of 152-154? Planning on heating sparge water to 168 and then doing my normal 2 step batch sparge follwed by the hops and a quick 15 min boil and the pitch clean ale yeast. Am I missing anything?
Wondering if my coller will hold the temp around 110-120 for 48 hours if the room temp is at least 70F and wrapped in heavy towels?

Oops, for got to mention I will use raw uncrushed grain in the mash for the lacto.  Also, do I drain after souring then sparge or add first sparge addition and then drain?

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There can’t be too many berliner weisse threads.

I suspect your cooler won’t hold that temp for 48 hours, but it might depending on how well it is insulated. Of course, the way to guarantee it won’t is to open it up to check and let all the heat out. I’d preheat with hot water, wrap with towels, etc. The brew heater won’t hurt either.  You could test heat retention by filling with hot water and letting it sit for 24 hours.

I’ve never seen a full mash souring done. My friend who does lots of berliners mashes and sparges into the cooler, then adds 1lb of raw grain to the wort to inoculate. I’m not sure what he mashes at, though I’d imagine it is in the 152 range.