Double retort still alcohol levels

[Revival rum]

When I am doing a distillery tour and explaining the way my double retort still works. I'm never really sure what the alcohol levels will roughly be between the 3 vessels.

Our wash starts at 7.3%ABV in the main still, the first retort is charged with 50.4% ABV and the second retort with 48.5% ABV. Our Heart cut is around 79.5% ABV.

What would a fair approximation be to tell them?

[Kindred Spirits]

The easiest way would be to pull a small sample mid run (if possible to do it safely) and check the ABV on it. Each system is different, and those numbers will change throughout the run too depending on how long you are into the run.

[Revival rum]

2 minutes ago, Kindred Spirits said:

The easiest way would be to pull a small sample mid run (if possible to do it safely) and check the ABV on it. Each system is different, and those numbers will change throughout the run too depending on how long you are into the run.

Unfortunately I don't have a safe way of doing that. What are the ballpark figures likely to be?

[Kindred Spirits]

Do you have a picture of your still? 
It would be hard to say exactly, but at some points of your run both retorts would be pretty close to your outlet ABV.

The first one would be higher first, then transfer over to the second, and then out the condenser. What are your final ABVs in each after a run?

[meerkat]

You can get a ballpark estimate from the boiling points.  It is usually much easier to mount a temperature gauge than to extract a sample.  I will attach a graph showing how the boiling point varies with the ABV of the boiling liquid.

Unfortunately this data is for atmospheric pressure and the temperatures do increase a bit with the back pressure from the retorts. You might find that the temperature in the pot still is about 2 degrees C higher than what the graph predicts and about 1 degree in the first retort. It is quite difficult to correct the boiling points for the pressure changes, but a simple graph is probably as far as you want to go on a distillery tour.

I will also attach a graph showing how the ABV of the vapour varies with the ABV of the boiling liquid.  This shows quite clearly how it is much easier to increase the ABV in the beginning of a distillation than it is once the ABV get up above 40%

Carey and Lewis MF Mass and ABV - Liq vs Vap Graph.pdf Carey and Lewis MF Mass and ABV - BP Graph.pdf

[Revival rum]

5 minutes ago, meerkat said:

You can get a ballpark estimate from the boiling points.  It is usually much easier to mount a temperature gauge than to extract a sample.  I will attach a graph showing how the boiling point varies with the ABV of the boiling liquid.

Unfortunately this data is for atmospheric pressure and the temperatures do increase a bit with the back pressure from the retorts. You might find that the temperature in the pot still is about 2 degrees C higher than what the graph predicts and about 1 degree in the first retort. It is quite difficult to correct the boiling points for the pressure changes, but a simple graph is probably as far as you want to go on a distillery tour.

I will also attach a graph showing how the ABV of the vapour varies with the ABV of the boiling liquid.  This shows quite clearly how it is much easier to increase the ABV in the beginning of a distillation than it is once the ABV get up above 40%

Carey and Lewis MF Mass and ABV - Liq vs Vap Graph.pdf 20.11 kB · 0 downloads Carey and Lewis MF Mass and ABV - BP Graph.pdf 20.77 kB · 0 downloads

Many thanks meerkat I will use these as my ballpark figures.

[Bolverk]

I've used the thumper calculator on HD and it's pretty close. For double thumper use your boiler abv as your first retort and the thumper as your second retort 

https://homedistiller.org/wiki/htm/calcs/calcs_haggy_pot_plus_thumper.html

 

[Revival rum]

@Bolverk Thanks for this, it's a good way to cross check figures.