Pre-boil Gravity

[tdack]

I've been venturing into making a few beers using unhopped LME, a kilo or two of steeped grains, DME, boil it up add hops at the right time and Robert is your mothers brother. So far the results have been quite pleasing to the palate.

At the same time I've been putting my recipes into BeerAlchemy (Mac brewing software) and trying to match what I do (or have done) with the numbers that is spits out.

What I don't seem to be able to get a handle on is the "Pre-boil Gravity".

Do I take the sample for the pre-boil gravity after steeping the grains and sparging (I'm pretty sure that the 3 litres of 70C water I pour through the grain bag is classed as sparging)?

I think I've been taking it after addding the LME and the DME which probably explains why it is fairly high and doesn't match what BeerAlchemy thinks.

Cheers.

 

[wambesi]

I never bothered with software or much measurements when I was doing extract, but your pre-boil gravity is taken after all the malts have been added/steeped etc and you are now ready to boil and add your hops.

However what size is your boil? Is it smaller then you add water to the fermenter to top it up? If so it would not read correctly as it will be concentrated, however if you are doing a full volume boil then you should get the right amount.

Hope that helps.

 

[tdack]

My boil has been about 8 or 9 litres once the cans of LME and the DME are added. Prior to that it is around the 6 litres mark (3L for steep, 3L for sparge). This then gets topped up to 21-23L depending on how much attention I'm paying as I tip jugs-o-water in.

 

[wambesi]

My boil has been about 8 or 9 litres once the cans of LME and the DME are added. Prior to that it is around the 6 litres mark (3L for steep, 3L for sparge). This then gets topped up to 21-23L depending on how much attention I'm paying as I tip jugs-o-water in.

Then I would say your pre-boil gravity wouldn't match up with software as it is concentrated and not complete at that point, there may be some equations or something that could help out but I'm not sure as to that.

To be honest though, I never worried about pre-boil gravities until AG, and even now I don't worry about it too much.
Does your OG meet up with what the software predicts?

 

[tdack]

Then I would say your pre-boil gravity wouldn't match up with software as it is concentrated and not complete at that point, there may be some equations or something that could help out but I'm not sure as to that.

To be honest though, I never worried about pre-boil gravities until AG, and even now I don't worry about it too much.
Does your OG meet up with what the software predicts?

OG meets with predictions so I haven't been too worried about. I mainly asked because the software has volumes for before boil, after boil, amount transferred to fermenter and amount added to reach target quantity. So from that I figured it would be doing some maths to figure out the pre-boil gravity based on the volumes that I plug in.

Anyway, as you said, as long as the OG is in the right vicinity and the beer ends up tasting good, then I've nothing to worry about.

Cheers!

 

[wambesi]

OG meets with predictions so I haven't been too worried about. I mainly asked because the software has volumes for before boil, after boil, amount transferred to fermenter and amount added to reach target quantity. So from that I figured it would be doing some maths to figure out the pre-boil gravity based on the volumes that I plug in.

Anyway, as you said, as long as the OG is in the right vicinity and the beer ends up tasting good, then I've nothing to worry about.

Cheers!

Most of those would be to work out efficiency which is really targeted at all grain, so honestly I would not worry to much about them at this point. You may be able to play around with the values to meet up with your boil volumes etc but as long as your OG is around the same everything should be all good!

Glad to help.

 

[kevo]

I use a formula I heard on the BN to sort my OG;

Pre boil grav X vol = post boil grav X vol

Then just switch the values around to find the value you want.

I do partial mashes, and add my extract in the last 10 minutes. I add my liquid from my mash and get up to my pre boil volume and take an SG reading.

While the boil is going, I get my preboil gravity, use the formula to work out how many gravity units of extract I need to add to get to my OG and prepare this through the boil to add in the last 10/15 mins.

This is handy as my partial mashes can be really good and then other times really ordinary. Using this formula I often either hit my Og or am within a couple of points. Might be fiddly with a concentrated boil, but it could be handy.

Hope that helps

Kev