an all grain question for a novice

[beechwood]

I've been doing kits for years and now thinking of doing some all grain brewing, I've got a cool box which I assume I could use as a mash tun, however my stock pot is only about 13 lts in size.
my question is this how much water will I loose due to evaporation during the boil, I was thinking about 40%??
I don't mind doing smaller brews but I was wondering how much beer I would end up with if I started with 13lts.

also can you put a lid on it when boiling or is it best not to.

 

[Pjam]

My stock pot is only about 20 litres and I wouldn't risk putting more than 15 litres in. You could brew in two or three batches. Do one batch, add it to the FV, do a 2nd batch, add that to FV etc.

 

[fbsf]

Depends on how big vs tall your pan is - shorter flatter pans have a greater surface area for evaporation than thinner taller ones.

With my 33L FV boiler on a good rolling boil, I normally expect to lose about 3.5L per hour, so if your pan is a little smaller than that, I would reckon on about 3L/h.

Therefore, once you have lost a litre due to the hops, you'd be getting around 9L, or rather conveniently, 2 gallons! I've done single-gallon AG brews before and they haven't suffered, so go for it.

There's also nothing stopping you boiling in two batches and bunging each in the FV once it has cooled...

 

[Robbo100]

Many recommend not to put the lid on by the way, because it can cause some off flavours.

 

[fbsf]

The lid thing is a bit dependant on what malts you are using. If you are using a well modified malt like Maris Otter, then it shouldn't be too much of a problem, but some of the other malts can suffer if the DMS (Dimethyl Sulphide...I think) isn't boiled off. Gives it a bit of a cooked sweetcorn taste if I remember correctly.

For what it's worth, I normally have my lid open about 2 inches and with Maris Otter, never get a problem.

 

[beechwood]

thanks chaps!! I may well give it ago soon.