A few Rum questions

[fourexes]

G'Day all, I have been running macstills rum recipe for a while now and super happy with the outcome but have always had issues with it never starting back up off the original trub/yeast cake, usually requiring the addition of more yeast. I have reduced the volume of dunder from the previous run to 5 litres thinking it might be a pH issue but still having issues.

Ive recently changed yeasts and managed to kick a second generation off nicely without addition (restarted itself within an hour) and all went well until the 3rd which was really slow to start and has been slowly working away for 3 weeks now. It's still bubbling slowly so I'm guessing there's still sugar and yeast that's active. Would anyone have any idea what's giving my yeast such a hard time? Im leaning towards pH but haven't got a means to test yet.

Also I've included a picture of my makeshift dunderpit, I've had this going for a few generations now and usually add half of it to a new ferment then top up with the boiler slops from the last run.

Every new ferment smells better and better so I think I'm on the right track. Can anyone confirm for me please?

[Clickeral]

What temp are you adding additional liquid to the previous gen yeast bed?

[howard]

sounds exactly what happened to me when i started mac-rum.
3rd or 4th just stopped fermenting using the old trub and 10l of dunder.
i was adding 10L of dunder, but reduced that to 5L and use fresh yeast.
some folk have used the yeast for several generations, but my ferments were grinding to a stop.
so after a stripping run, i now put boiling dunder on the trub with the molasses & sugar for the next brew, top up with filtered water and add fresh yeast.
sounds like you have a PH problem.
are you using any oyster shells for PH control?
are you adding dunderpit to the ferment? i've not been that brave yet lol.
i only add from my dunderpit to the spirit run so far.
do you add the dunderpit at the start of ferment or part way through?

[bluc]

:text-+1:

[fourexes]

Clickeral: I always only add a few litres of tepid water till I'm done ginning around with everything else. I also loosen up the molasses and sugar in boiling water separately and let it cool so I don't shock the yeast. By the time I get it all together it comes up to about 28⁰.

Howard: I been having the same troubles as you for the past 5 years. Was only coincidence I changed from lowans to manildra yeast and tried the second gen again and it took off like a shot. The third however has been the slowest ferment I've ever had but it has some awesome caramel notes about it so I'll let it fizz, allbeit slowly. I was tempted to add some yeast or some Epsom salts but I really think it's a pH problem. The tap water is slightly alkaline do I thought it would balace it out but obviously not. I should just invest in some litmus strips.

I've been adding backset and Dunder to the ferment for a while now and it just keeps getting better as the pit gets funkier. I think rum washes are to fast and violent to worry about infection but I could be very wrong.

[howard]

apparently litmus papers are hard to read with rum washes, there's a few cheap PH testers on fleabay that work ok.
i keep a sample of 4.01 & 6.86 in mason jars in the fridge, shallow enough to dunk the tester in for 10-15 minutes before using.
do you boil the dunderpit liquid before adding to the ferment or just as it is?
i was thinking of adding some live dunderpit about 2/3 days into the ferment.
both my pits are enjoying the warmer weather now, did a spirit run yesterday, stunk the place out.
BTW do you add the oyster shells?

[fourexes]

Cheers for the pH tester info. I think I've got an old digital one around from my fish tank days I'll try to find it.
I don't add oyster shells no, I've heard of using them but never been that keen.

Is usually just dump the live Dunder into the ferment straight up.

Bit of an update, I noticed some growth forming on the top today so went to run it, dumped it into the boiler and I took off again immediately. I'm assuming it was partially stalled. I've transferred it into a clean sanitised secondary fermenter and given the primary a good cleanout and the idophor treatment. Hopefully I can salvage this wash and run it in a couple of days.

Might just stick to new yeast additions and keep using the backset with live Dunder and try to focus on controlling pH before I try generations again.

[howard]

good luck with the salvage.
i did do a quick side by side comparison with/without oyster last year(?)
went something like this......

rum wash with oyster figures.xlsx

if you're not a beachcomber, they can be bought at pet stores as chicken oystergrit.
i used to hang about 1 or 2 cups of them in a hop sock in the wash,(now upgraded to a small S/S dry hop tube).