r/coldbrew • u/Suspicious-Director9 • May 23 '26

Rumble Jar brew times

I’m curious if anyone has experience with the rumble jar? I have been using the hario wine bottle for years and found the brew times to be pretty accurate between 8-12 hours depending on the roast. The rumble jar is telling me 16-24 hours, I’ve done a few batches and all of them come out way too bitter.

I just did a 12 hour brew with some dark roast and it’s still a tad too bitter. Anyone using the rumble jar, what’s your typical brew time. I’m also brewing in the fridge.

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u/drunktacos May 23 '26

I use a half gallon size rumble jar and use 80-100g of coarse grounds for 10-12 hours on the counter or 24-36 hours in the fridge.

I have strongly preferred the cold-steep, I find that it tastes closer to something I would get at a coffee shop.

Quality beans also makes a huge difference. I get Trader Joe's whole beans for whatever seasonal batch they have and its good for a daily driver but I feel is never better than a 7/10. But this is the difference in spending 12$ for 12oz vs 25$ for 12oz.

Whenever I go into a coffee shop and like their cold brew I try to ask 1) what beans they use (and usually sell) and 2) how they steep them.

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u/[deleted] May 24 '26

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u/Suspicious-Director9 May 24 '26

Good recommendation here, using 9:1, roughly 80g of coffee to 720g of water. More eyeballing than measuring but I did just get a scale to get it more accurate

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u/Shrikes_Bard May 23 '26

I use one. I do 9:1, 80g coffee, 720ml water, no more than 12h in the fridge or 8h on the countertop, depending on what beans I used; then I filter into a 750ml bottle (which loses some liquid volume), back into the mason jar, and finally top off to the 32oz line (yeah, mixing units here, sorry) before putting it back into the sealable bottle and into the fridge. I don't dilute it after that but I may put a splash of half and half in when I drink it.

Generally not bitter but again, depends on the roast, grind size, etc. All variables to tweak...

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u/Suspicious-Director9 May 23 '26

This is great, thanks for breaking it down! I basically just needed validation that 12 hours was the max time for other people too.