I made an app to work out gravity corrections

[philistine]

Hey Dudes,

Dunno if this is the right place to post this...
Anyway, I fell short of my target gravity on a brew day recently and thought there'd be a simple way to work out how much DME to add to correct it.
Lots of googling brought up a lot of discussion threads in various forums and articles, but nothing along the lines of a calculator.

So I made one. It works as a phone app on iOS and Android or through a browser

Its pretty simple - its just a spreadsheet uploaded to Openasapp.net
First you click on this link ->
https://oaa.app.link/launch-app-f43f73f9-acda-47c0-9ec9-85bfd323546d
and it takes you to a landing page with further instructions (no spam or foul play here I promise)
From there, follow the instructions to send the actual app link to your phone and open it.

Still needs a little fine tuning, its basically a spreadsheet hosted on a website with a cool interface.

Hope this is of use to someone!

 

[philistine]

Screenshot

 

[MHB]

I think there might be a slight issue there, DME is over 96% solids (the part that contributes to gravity) Dextrose Monohydrate (what we all get in bags) is only about 91% solids, so you actually need more Dextrose than DME.

The standard way to do the calculation is to use Sucrose (white sugar) as the basis of the calculation then apply a correction, i.e. if you needed 100g of Sugar to achieve the target OG, you would need 100*1.04= 104g of DME, and 109g of Dextrose to achieve the same outcome, LME is about 20% water, so you would need 120g of LME...

I suspect you have tried to do the calculations in the silly system. bit later today I'll dig up some more modern metric based equations, lot easier to work with when you get your head around them.
Mark

 

[philistine]

I think there might be a slight issue there, DME is over 96% solids (the part that contributes to gravity) Dextrose Monohydrate (what we all get in bags) is only about 91% solids, so you actually need more Dextrose than DME.

The standard way to do the calculation is to use Sucrose (white sugar) as the basis of the calculation then apply a correction, i.e. if you needed 100g of Sugar to achieve the target OG, you would need 100*1.04= 104g of DME, and 109g of Dextrose to achieve the same outcome, LME is about 20% water, so you would need 120g of LME...

I suspect you have tried to do the calculations in the silly system. bit later today I'll dig up some more modern metric based equations, lot easier to work with when you get your head around them.
Mark

Cheers mark - yeah I just pulled the figures to convert between DME, DEX and sugar straight out of the priming calc on Brewers Friend - I actually didnt give them much thought.
I'll have a read and revise

 

[MHB]

Just off the top of the head, I doubt the amounts we are talking about adding would have much effect on the volume of wort (probably less than the measurement error for additions under 1kg).
Working in Plato (oP) would be easiest, oP being %WW solids, if we use the numbers in the post above "Target Gravity
If we want 20L @ 1.050 (12.5oP) we want (20*1.050) = 21Kg of total mass, that would contain 21*12.5/100 = 2.625kg of extract.
We have 20L @ 1.040 (10oP) or 2.080kg of extract.
We need to add 2.625-2.080 = 0.545kg or 545g of solids

We want to add 0.545kg of solids, that assumes that what you add is 100% solids (i.e. Sucrose) we also need to account for the moisture content.
Dextrose Monohydrate is ~91% solids so it would be 0.545*100/91=~599g
Dry Malt Extract (DME) is ~96%solids so it would be 0.545*100/96=~568g
Liquid Malt Extract (LME) is ~80%solids so it would be 0.545*100/80=~681g (same for Honey)

Mark

 

[philistine]

Dry Malt Extract (DME) is ~96%solids so it would be 0.545*100/96=~568g

I was pretty close though! only 10.7gms off!
Do those figures you've got there come from using the bog standard 43 ppg contribution factor for DME though?

If you change the contribution factor to 42.2ppg, you get 567.9 gram DME

(for some reason I found it way easier to have all the back-end formulas in the spread heet to work in US imperial measurements and then convert the results into metric)

 

[MHB]

Don't use ppg as I don't work in either pounds or gallons!
The modern metric approach is mostly based on Percent Yield, say you had 1kg of malted pilsner that had CGAI (Coarse Grind As Is) potential of 75% and a 80% efficient brewhouse, from 1kg you would get 1.000*0.75*0.80 = 0.600kg of extract.
From there its pretty simple to workout how much of that malt you would need to make any sized batch.
Say you wanted 20L @ 1.050 (12.5oP)
Total mass needed = 20*1.050 = 21kg
Of which 12.5% is extract so we need, 21*0.125 = 2.625
We are getting 0.600kg of extract/kg of malt
2.625/0.600 = 4.375kg of malt

The standard equation is usually expressed as
Grain Weight = (Volume cool wort*SG*oP) / (CGAI*Brewhouse efficiency)
G.W. = (20*1.050*0.125)/(0.75*0.8) = (2.625/0.6) = 4.375

Way easier than silly system once you get your head around it.
Mark

 

[philistine]

I just edited my post before I realised that you'd replied.
If you change the DME "contribution factor" to 42.2ppg, you end up with the same figure you came to in your post above (568gms DME- or 567.9gm to be precise)

but yeah - imperial does kinda suck, but in some ways it does make sense.

 

[MHB]

Old enough to have had to learn it at school - the Imperial version not the US one.
Sorry don't agree, it makes no sense at all. Not only that all the malts we get in Oz are certified in EBC/Metric units so thee point of converting the information from metric > imperial - doing the calculations > back to metric, escapes me.

Attached is a COA for the new Cologne Malt from Weyermann, Have a look at the information we as brewers get to work with.
Mark

 

[philistine]

Yeah youre right.. it makes no sense
Though I seem to remember reading something about volume measurements and the invention of the 'litre" as a unit (or was it mass and kilogram....) anyway, the point was that the origins were just as obscure and subjective - if not more so - than the imperial system.... damn I wish I could rememember/find it, it was an interesting idea...


anyway, with the calc, i just found it a lot easier to find info online re; brewing math in US imperial measurements. It seems that most literature thats easily accessed and readily available is written in 'merican. The formulas were all pretty much just copy/pasted into Numbers (Numbers is the Metric version of Excel ;-) )
At the end of the day, I wasnt doing it for Uni, I was doing it for results, and the results are pretty much the same