First Ag- The Aftermath

[TasChris]

Can't see how the % loss during boil works.
Why would the amount lost during boil change if you have more or less volume in the same container and under same conditions.

If you say loose 10% when boiling 40L ie 4 L, why would you only loose 3L if you boil 30 L, i still think you will loose 4L not now 3L or if you boil 50L why would that increase to 5L.

In my simple mind the same volume is lost regardless of total volume unless the extended time taken to get say 50L to boiling compared to 40L is the cause.

Cheers
Chris

 

[Scruffy]

:anticipates...:

 

[Bribie G]

If you check Mark^Bs figures and mine, they are just about identical if you add 3 litres to both his figures. Also a 90 minute boil will really shrink the wort, whenever I do a 90 minute job I usually almost end up with a full urn after dough in, using around 35L strike liquor to start off with.

Edit: the boil off occurs at the circular interface between the wort and the air, and will indeed be the same litres boiled off regardless of whether you start with 25, 30 or 35 in the urn. That's where the percentage comes in. The number you really need to establish for your particular pot is litres per hour.
To take two ridiculous extremes if your urn was tall enough to reach down to the centre of the Earth but only 35 cm wide you would only lose the same LITRES as if your urn was only 40 cm high. (all other factors being equal which they wouldn't be). Similarly if your pot was a centimetre high but as wide as an Olympic pool then again you would lose the same litres but they would all go "whoosh" into steam in about half a second.

 

[TasChris]

Where I was heading was, didn't make myself very clear, that it is better to use a set volume loss per hour rather than the % of boil volume to plug into the software. I have found that the % loss leads to significant final volume discrepencies if you change batch size

Cheers
Chris