Wash Strength Determination

pogriallais

Hi guys,

I have been using a 3 plate 5 inch dash column to distill a Poitín product for the past number of months. It has been going well until the past 3 weeks. I'm getting very poor yields. The fermentation looks to be working well. Initial gravity is usually 1.061 and final gravity is usually 0.997. I'm only getting about 3 litres of a heart cut before it goes into feints. I have tried increasing reflux but it hasn't extended my hearts cut by much. I'm currently measuring my total alcohol from the still to see if it matches the wash potential. 250 litres of wash at approximately 8%ABV should yield 20 litres of pure alcohol. My fores are normally 5% of the 20 LPA. Hearts are normally 60% of the total LPA. Feints are usually in the region of 35% of the total LPA. Is there another method of testing the wash and could the hydrometers be giving a 'false' reading? I take readings at 20 degrees centigrade.

Smaug

Have you checked your rig for leaks?

pogriallais

I have. The gaskets appear on close inspection after removal appear perfect. I have collected all the alcohol from heads to feints and the full 20 LPA is in the pot, none was lost to leaks. The congener balance is out and the tails are more prevalent than hearts. No amount of reflux could compress the tails anymore. The classic fogging of the sight glasses was apparent just before getting into tails. The PH of the wash is worrying. At 3.6 it suggests infection.

pogriallais

For reference the heads cut was 500ml @ 92% ABV, hearts: 4.1L @ 88% ABV, Feints 52L @ 25.5% ABV. Total LPA collected 19.88. A very small amount of alchol remained in the still but I wanted to collect to ensure I wasn't losing any alcohol through leaks.

jacksonbrown

So you lost 30LPA?
It shouldn't be too hard to find :))

trebor

How are you making your cuts?

crozdog

Without a lot of detail, it appears that the wash is fermenting out well - you say "Total LPA collected 19.88". This leads me to suspect ingredients or process changes.

Are you using the same Ingredient supplier? is the ingredient quality the same? Have changed the water used eg town instead of rain??

Have you compared a previous run with this - especially the fermentation? FYI pH of 3.6 isn't that low. under 3 is.

How does the wash smell / taste compared to previous? If it smells / tastes the same, it probably eliminates the ingredients, mash regime, and fermentation practices. That leaves the still run.....

Have you tried collecting the entire run in say 500ml containers, taking copious notes during the run including ABV of each jar (try using the record sheet in the back of my manual) airing for a day or 2 then coming back and doing your cuts?

IMHO your original cuts are out ie 5% fores, no heads and 60% heads with 35% tails. I don't make the potin, but most of my output is around 20% fores & heads, 50% hearts & 30% tails.

Not trying to teach you to suck eggs, but have a read of ZBob's & Kiwi's guides:

• Zymurgy Bob's Distillation Facts: Making the Cuts
• Kiwi's Guide To Cuts

Sounds like the alcohol is there - not just where you expect it...

I use lots of reflux to stack the fores / heads, not the tails. I find fogging only occurs right near the end of a run, not as the tails come on. The viscosity on the site glass definitely changes in late tails which I use as an indicator to turn the rig off.

jacksonbrown

Is it possible for an infection to consum 60% of the fermentables?
You'd notice right?

pogriallais

Just to add some more detail. The ingredients are the same. I did get a new batch of dried yeast as I felt the older batch was a little slower to reactivate upon rehydration. For a wash made of malt only a ph of 4 is the average. Below that indicates bacteria in Ireland/ Scotland at least. I don't sense a great deal of difference in the last 3 batches versus what I used to have. I do notice much more foaming in the fermentation vessel. I have tried adjusting the temperature of the wort when pitching yeast. The weather is slightly colder so I raised the wort temperature to 22C. When rehydration the yeast I used 50:50 water and wort. I actually boiled the wort prior to using it for the yeast to kill any bacteria present. In my experience I never came across the foggy glass until the end of the hearts cut. I assumed by increasing reflux that I could keep the relative volatility of the water alcohol mixture high. Maybe I need to reduce the reflux?

grim

IMHO...

Tails = Fermentation Temperature

Heads = Infection (or if larger than usual tails cut, also Fermentation Temperature)

pogriallais

So would you recommend fermenting at a cooler or warmer temperature? I'm thinking cooler?

grim

What temp do you pitch at? What temp do you ferment at? What was peak temp? What is your ambient temp? Do you have active cooling of your fermenters?

pogriallais

Pitched at 21C. No temp control in the fermentation vessel. Peak temp is usually 30C. Ambient is 8- 15C. I was pitching at 19C during the summer when Ambient temp was average of 14-19C.

pogriallais

So just to update everyone on the cause of the whole early onset of feints situation. The cause was a residue left by a juniper spirit run I did. A hot caustic wash didn't prevent it from happening. I discovered the film by using steel wool to polish the stainless steel and copper plates. They looked clean from observation but if you ran your fingers along the inside of the column the stainless had more friction than usual. After polishing the column the column operated perfectly again, the plates filled up with spirit again and the spirit flowed in a nice even stream. While the problem was ongoing the rate of condensed spirit coming off was erratic. I wanted to share the solution with anyone who may come across it themeselves. The wash was perfect, so a lot of time wasted trying to solve a problem that didn't exist.

CothermanDistilling

Caustic and steel wool are damaging to copper, I use PBW (powdered brewery wash) which was developed to not eat copper.. you need to get it pretty hot, 70c+ for it to take off the gunk...

geoff400

Thanks for the feedback @pogriallais I am starting a gin journey so it is very useful information. I must admit so far I have been doing minimal flushing as I have not been doing any other kind of spirit. Do any regular gin distillers have a recommended regular cleanup routine?