Problems with Rum Fermentation

[Vurumai]

Doing BB's Rum. Molasses ferment with yeast from previous ferment goes OK for 2-3 days then stops. Been dissolving the raw sugar in water then adding it. The fermentation kicks back on then stops. pH very lot at about 4.0 so I bring it back up to about 5.0 with what seems like a lot of baking soda. Double checked the pH with strips and it is still in the ball park. Added some yeast nutrient, repitched DADY yeast and nothing. Not a bubble. Ended up moving half the wash into another bucket and diluting by half with some warm water and that got it going. I suspect that the addition of the sugar made things too concentrated and the yeast did not like all that osmotic pressure. I started adding the sugar mixture in smaller aliquots and mixing more but the fermentation still stops until I dilute it. I gave up on taking SG on molasses ferments because it just give me crazy numbers. I am mixing gently and trying to aerate.

Weird thing is my first molasses and sugar ferments went off without a hitch. Is there a way to make this go smoother?

[NormandieStill]

Doing BB's Rum. Molasses ferment with yeast from previous ferment goes OK for 2-3 days then stops. Been dissolving the raw sugar in water then adding it. The fermentation kicks back on then stops. pH very lot at about 4.0 so I bring it back up to about 5.0 with what seems like a lot of baking soda. Double checked the pH with strips and it is still in the ball park. Added some yeast nutrient, repitched DADY yeast and nothing. Not a bubble. Ended up moving half the wash into another bucket and diluting by half with some warm water and that got it going. I suspect that the addition of the sugar made things too concentrated and the yeast did not like all that osmotic pressure. I started adding the sugar mixture in smaller aliquots and mixing more but the fermentation still stops until I dilute it. I gave up on taking SG on molasses ferments because it just give me crazy numbers. I am mixing gently and trying to aerate.

Weird thing is my first molasses and sugar ferments went off without a hitch. Is there a way to make this go smoother?

I am far from a rum expert (have a carboy of low wines from my first BB rum wash waiting to be run), but a few comments.

- pH of 4 does not seem that dramatic, but baking soda is not the best way to get it back up. Baking soda contains sodium which will upset the yeast in large quantities (like the large quantities that you added!). You're much better off using calcium carbonate. Did you check BB's table of recipe adjustments based on starting pH of water? It's in the thread somewhere. Normally if you follow the guide you should have too many issues.

- SG should be OK for monitoring purposes even if the values don't seem to make a lot of sense. You should see a decrease in SG over the first 2 to 3 days which levels out a little. A spike when you add your sugar, and then a drift back down until you level out again (hopefully at or lower than where it stopped initially).

- Once the wash has started, you don't want to aerate or the yeast will (more or less) stop making alcohol and go back to making more yeast.

[jessespa]

It seems like something must be off with this batch since the first one didn't have any problems.
I also don't think pH 4 is that bad. I also wouldn't use baking soda. Pickling lime is what i use to balance out my pH.
I agree SG really doesn't give you a whole lot as far as SG and FG readings but it could help you see if it is actually doing something or anything.
I've had very little problems with the pH on the rums I make but then again i use oyster shells in my wash and they do get used up so they are definitely doing something.
Not sure but there are alot a variables as to why you are having a problem. Has your temperature dropped in the fermenter? I know if temp drops it will slow your yeast activity down to nothing.
Also i haven't used DADY yeast on my rums but cant believe it would have much difference. I use regular bread yeast on my recipes.
Maybe a recipe error? Any chance we can we your recipe amount of water to sugar and molasses ratio?

[Sporacle]

First step of trouble shooting and I know it would be a really fast ferment. Was it done?