Mash/boil numbers don't add up?

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Welcome to BIABrewer Simon ,

That's a mighty big brew you have done .

Mad_Scientist wrote:Actually, your pre and post numbers nearly balance.

What MS is saying here is correct. To determine this he would have done the following quick volume x gravity calculations...

44.7 L @ 1.060 = 44.7 * 60 = 2682
30.7 L @ 1.091 = 30.7 * 91 = 2794 All is good!

The above are well within 5 percent of each other and that is great as it is very hard to get two sets of measurements to match exactly at our scale of brewing.

But, let's do the same check on the Beersmith estimates...

42.3 L @ 1.058 = 42.3 * 58 = 2453
33.3 L @ 1.089 = 33.3 * 89 = 2964 This is not correct.

Those numbers are estimates and therefore should match (amount of 'sugars' in the beginning of the boil equals amount of 'sugars' at the end of the boil) but are 20% different.

Beersmith has several volume and gravity errors but when you do the above calculations, the error is only 4% so something else is gong on here. (Also note that some errors in BeerSmith1 are not in BS2 but several are still in both. Reading the entrails can get tricky.)

I would post your .bsm file up here so as we can take a look (see Note below).


PP

Note

I usually avoid answering Beersmith questions now as it takes so much time to explain the formula errors, terminology and things that can go wrong but it looks like you have a solid understanding of the basics so I'll see if I can quickly find what has gone wrong if you post the file. Remember though, the numbers will never add up perfectly in BeerSmith until some errors get fixed.

Also because of the above, BIABrewer has created the BIABacus which, despite its primitive spreadsheet form, is still far easier, faster, safer and more powerful to use. It does things like auto-estimates your kettle efficiency. For example, in your recipe, you wouldn't have had to guess at a 'mash' efficiency, the BIABacus would have done that for you (75.9%). Your numbers will also always 'add up' in the BIABacus.

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Well this one nearly beat me Simon but I have found the problem in BeerSmith (and another two) ,

I don't want to write about the BIABacus in this post but this thread is a great example of why this site has been working so hard on not only the BIABacus but clear terminology as well. (A quick look at the BIABacus will have scared you but a slightly longer look, while having a beer over say 20 minutes, usually gets you over the initial hump .)

I will write a bit though on finding the problem as all the work below is caused by formula, terminology and design errors.

Finding the Problem

Like so many problems in other programs, this one took some time to find as the programs not only have errors in some formulas but their lay-out and terminology make things extremely difficult to investigate. The answer might look easy in the end but here's what I had to do to solve the problem and, I had an advantage to start with, I already knew that Beersmith has two 4% errors in it. One has to do with volume and the other with gravity. The latter is irrelevant in this thread.

We know that volume x gravity pre-boil should equal volume x gravity post-boil but your recipe showed a 20% difference. Why???

1. First thing I did was look at your equipment profile but that looked fine to me. (One problem with your liquor to grain absorption ratio - it's using traditional absorption not BIAB absorption ratio for some reason).

2. I knew that there was a 4% volume error in BeerSmith that was relevant in this case but as I hadn't looked at that in a while, I thought I better check it again. I picked some sample recipes and, as luck would have it, found that the first three I picked were showing discrepancies different from 4% - what the???

3. Changed the gravity readings to 6 decimal places as 2 decimal places can give you a few percent variance. This got the pre and post-boil discrepancy reading around 4% for most recipes except two.

4. Looking at the two recipes above, saw they were from the same brewer. Opening up his equipment profile, you can see he uses top up water in his fermentor. If you remove that top up water, his discrepancy also changes to 4%.

...

So, that is one more error. 'Post-Boil Gravity' in the BeerSmith Recipe rReport does not really mean post-boil gravity.

This still hadn't sunk in fully at this stage and after another 5 minutes of looking at your recipe and your 'Brew Steps' I was about to give up when...

5. I finally saw there was 950 grams of corn sugar buried away in 'Fermentation Ingredients' of the 'Brew Steps' sheet. (Note this appears after the end of boil gravity estimate.) If you delete this from the recipe, you will get the same 4% discerepancy.

Problem Solved .

Here is the excel file I ended up with while investigating this - lol

BeerSmith2 Pre and Post Boil Estimate Discrepancies.xls

Note: The order of the recipes in the excel file attached is actually edited. In reality, finding the discrepancy was a lot harder as some of the discrepancies that varied greatly from 4% originally appeared first.

Conclusion

Post-boil gravity in BeerSmith2 is not correct if priming sugar or top-up water are included in the recipe.

Finally

These are actually two new problems that I hadn't found before. You might be able to imagine how difficult some other problems were to find and, worse still, how difficult they are to explain to a new all-grain brewer let alone an experienced one .

One good thing Simon is that, from your writing, I think you have your head around some of the main design shortfalls of existing software. Showing an understanding that there are at least two different types of efficiency is pretty rare and impressive. Such an understanding is the most basic requirement to even begin using those programs correctly but 'kettle' efficiencies, let alone 'fermentor' efficiencies are the last things any new brewer should be expected to predict/know. In fact, kettle efficiency is 'sold' as being a constant by existing software but in reality, it is not.

The BIABacus uses 'intelligent' formulas to look at your recipe and calculate your kettle and fermentor efficiencies for you so a knowledge of any type of efficiency is totally unnecessary unless the BIABacus draws your attention to it.

Also note that it took me two computer screens and, for every recipe, the opening of five BeerSmith windows to get the same information I can get on the first sheet of the BIABacus. That first BIABacus sheet might look big at first but it's not actually that hard and has more critical/valuable info than you will find anywhere else, despite the lack of drop-down lists. Grabbing a beer and going through the A to Z of it over twenty minutes - make 20 mins your time limit (don't get stuck on one thing), will give you access to a whole new world and save you hours.

...

I hope the above hasn't been too much to take on board Simon but the aim on this site is to try and get a complete answer for you as soon as possible rather than being swamped with a hundred posts that could be wrong or right.


PP

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No problems Simon, it was actually a great time for me to re-visit some problems I knew about plus your thread lead to the discovery of a few more. As for, "not getting it", it is a really hard area to get...

1. Firstly, you have to at least realise that...

...hold on, if I keep writing all the things you have to understand we will get lost in detail. The first thing that you have to accept is that there are some very basic errors in BeerSmith (and other programs). In this thread so far, I have only mentioned them, I haven't explained them because they are so tedious to explain...

We have volume shrinkage and expansion errors combined with grain moisture content errors which affect not only volume and gravity estimates but also colour and bitterness estimates.

On top of all this, the errors in BeerSmith1 were even more pronounced - it's a long story but, in essence, you and I could brew exactly the same beer with exactly the same equipment and end up with two completely different coloured/bittered beers depending on your kettle trub management. Obviously, that was totally incorrect.

Am I for Real? Is this for Real?

At this stage Simon you might be asking if I am for real . I've spent seven years studying this stuff and have been totally gob-smacked at some of the errors that appear in software. I understand that you are asking me questions such as you asked in your post above... "It seems the volume and SG issues in Beersmith are a product of its inability to include boil-added Dex into its calculations, is that how you see it?" Well, yes, but that is only the smallest part of many problems that exist. There are so many more unfortunately.

Auto-Scaling Options

That was very good of you to have another look at the BIABacus Simon . You have written that it does not offer enough auto-scaling options but auto-scaling options in that context are another myth.

A recipe can only be scaled in one way and the BIABacus does it virtually instantly with no distortion.

...

I fear I have written too much already so I better leave it at that however, maybe you scaling the Pliny recipe to another equipment profile will help illustrate what I mean.

Maybe create a totally different equipment profile in BeerSmith and scale your recipe to it? Once you have scaled it (there are five, maybe seven, different ways of scaling in BeerSmith2 that I have found so far*), post the .bsm file up and I'll be able to show you where the recipe has been corrupted/distorted.

Doing this can be an interesting exercise.


PP

* If someone does enough googling on Beersmith2 beta testers they will find a whole essay on just this one issue.

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Sorry Simon, I was hoping to find time early today to re-write my last post above into something more useful - too much fuel on board writing that one . What I find very hard when dealing with other programs is working out where to draw the line in explaining their potential problems. I think the best thing I can do here is mention just one issue when scaling using certain software.

Auto-Colour Adjustment immediately Compromises Recipe Integrity

When you scale a recipe in BeerSmith2 and some other programs to a different set of equipment, the program alters the recipe automatically so that the colour stays the same. How does it do this? By changing your grain bill. This immediately compromises the integrity of the original recipe.

For example, I just scaled a mock recipe from one profile to another and my grain percentages changed as follows...

Pale Malt - 89.3% to 84.5%
Caramel Malt - 8.9% to 12.8%
Black Malt - 1.8% to 2.6%

Firstly, the colour estimate formula we use in software is very primitive so forcing a recipe to match a colour may not even have the desired effect in real life. This doesn't worry me much but the next point does.

Nearly all malts that contribute colour also contribute a unique flavour. In the above recipe, on a single scaling, we have increased the flavours contributed by the caramel and black malt by over 40%. This means we have compromised the flavour profile of the original recipe substantially.

Note that nearly all people using BeerSmith scale in the above manner. I think it is important to be aware of this.

One More Recipe Scaling Problem

The critical things in recipe scaling are the OG, the percentages of the grains used, the hop weights and AA% and how the hops are managed (eg, addition times etc) and the volume at the end of the boil once chilled. We are now calling this the, 'Volume of Ambient Wort (VAW)'. [Note that the BIABacus files you come across atm are probably using an older term, 'End of Boil Volume - Ambient (EOBV-A)'].

The following bit is a bit tricky but it is the only tricky thing anyone needs to get their head around so relax and grab a beer ...

Volume of ambient wort is essential for correct recipe scaling but this number is usually difficult or impossible to find in most published recipes. Instead what we usually see in published recipes is the term 'batch size'. There are many problems with this...

1. By 'batch size', the publisher of the recipe may mean desired, 'Volume into Fermentor (VIF)'. If they do mean that, unless they also publish their 'Kettle to Fermentor Loss (KFL)', you will not be able to determine the critical number - VAW.

2. What happened in BeerSmith1 was in order to work around certain formula errors, many users started to set up their equipment profile as follows, 'Batch Size' = to VAW and 'Loss to Trub and Chiller' (our KFL) as equal to zero. Sounds good for us right? Well...

Unless you download the actual .bsm file or are lucky enough that the publisher has used one of only two reports that show you the value for 'Loss to Trub and Chiller', it is impossible to know what method above the original author has used. (Occasionally, if you have a very advanced knowledge of the software being used and its errors, you can deduce the VAW but it is very time-consuming.)

The above problem is a very hard one to accept mentally as you are being asked to accept that nearly every recipe you come across is either very difficult or impossible to scale accurately. [Also see the Does this recipe have integrity? Can I copy it? thread.]

Correct and Easy Recipe Scaling

Let's try and throw all previous thinking out the window. Forget ambiguous terms such as, 'batch size' and 'brewhouse efficiency' (this can also mean one of two different things for the same reasons mentioned in the last section) and let's make things easy.

Always think of Volume of Ambient Wort. This equals your Volume into Fermentor plus your Kettle to Fermentor Loss. Imagine two different brewers. Let's say both desire the same Volume into Fermentor, we'll call it 20 L. Brewer A though uses a hopsock, whirlpools etc etc and usually gets 2 L of 'Kettle to Fermentor Loss (KFL)'. Brewer B uses no trub management and gets 5 L of KFL. Obviously, brewer B needs to start with more ingredients than Brewer A.

I say, "obviously," but the above point is very difficult to catch on to because it is hardly ever talked about on forums or in books.

In your post above, you wrote about the BIABacus scaling according to "...desired volume into fermentor." More correctly, we'd say that it scales according to desired VIF plus KFL, in other words, it scales according to the Volume of Ambient Wort - the only correct way of scaling.

Using the BIABacus

The BIABacus has been designed so it works in a completely different manner to existing software. On one hand, a new user need know absolutely nothing about estimating evaporation, kettle to fermentor loss, fermentor to packaging loss, kettle efficiency or fermentor efficiency. All of these are auto-estimated. On the other hand, a more experienced user can alter defaults if necessary and/or do complex investigation of external recipes.

Going back again to your post above, when you wrote about changing the desired Volume into Fermentor' to scale a recipe, you were also correct in saying that. Assuming you have made no adjustments to the defaults, the BIABacus will grab that number and add it to the estimated KFL to determine the new VAW. It will look at your kettle diameter you enter in Section B to determine your evaporation. It will look at how much water actually comes into contact with the grain to determine the kettle efficiency ('Efficiency into Boil (EIB)' is an example of a kettle efficiency) etc, etc.

So, just by completing the few fields in Section B, any recipe gets immediately scaled to your equipment. The scaled ingredients will always appear on the right hand side of Sections C and D.

The only tricky part in scaling a recipe from an external source is, of course, determining what number to type into VAW (or EOBV-A) at the top of Section D. Often you will just have to take a guess.

Current BIABacus Limitations

It's also good to be aware of some of the limitations of the BIABacus in the current spreadsheet form. The biggest limitation is the inability to import and export recipes. This means that if you get a BIABacus file from someone else,you will always have to fill in Section B and any defaults or adjustments you may have made in Sections W and X.

A lack of grain and hop drop-down lists will be seen as a major limitation but in reality, this can actually be an advantage. Won't write on that here. The next one though is especially relevant with your recipe....

Your recipe has about a billion hop additions and unfortunately the BIABacus only allows for eight. It is very rare for a recipe to exceed 8 hop additions but it does happen. To get around this limitation, you really have to go through some clumsy stuff unfortunately. If I get time in the next few days, I might actually do this on your recipe.

The biggest current limitation I believe is the lack of written help and instruction on the BIABacus but time will solve that problem.

I hope the above clarifies more than confuses Simon . Some of the above concepts can take some time to really sink in and become simple/easy.


PP

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[NOTE: Simon, have written the below with several interruptions. Hope it reads okay and thanks for triggering something I'd never seen before - that bit is towards the end.]

Very pleased that it made sense Simon . Not many people are aware of the things we looked at above so you can put yourself into a very small league.

Apologies in advance, this might be another long post to cover some of your questions above.

...

Using Beersmith and the BIABacus at the same time: Sounds like a good plan using BeerSmith and the BIABacus to note the differences. Pay particular attention at first to things like how the BIABacus auto-estimates your efficiencies, individually, for every single recipe. Or how you no longer have to play the game of twenty questions when the hop you have has a different AA% from the hop in the original recipe. (We'll come back to twenty questions later here.)

...

Trub Management: As you have read, some people throw all their trub into the fermentor and notice no problem. Maybe they are right? But then again, maybe they are right for only certain beer styles and/or certain palates. (I can taste some faults my friends can't and vice-versa). I tend to just play it safe and try and avoid trub without it being an inconvenience.

Using your BIAB bag as a hop sock is a very simple and easy way to practice good kettle trub management so, if you can hang the bag in the kettle, why not do it?

As for the numbers question, if you threw all your trub into the ferementor, you would, in the BIABacus, set your KFL to zero but then, at a guess, maybe double your auto-estimated, 'Fermentor to Packaging Loss - FPL'. (Same thing can be done in BeerSmith just different terminology.)

...

Playing with a Recipe

(I'm assuming here that dextrose is a grain, which it isn't. Bear with me on this until you get to the end of this post.)

Above you wrote, "...say I wanted to 'play' with a recipe.... for instance, if I've keyed in the grain bill but then read that maybe increasing the Dex and decreasing the Pale Malt while keeping the OG the same, will help dry it out a little, how do I do that? ? It seems if I change the Dex up, all the grains change - but maybe that is exactly correct to maintain colour etc?"

Colour has no priority in the BIABacus, it is always the grain ratio and the original gravity. Let's say, in your situation, there were three grains in the bill and that no extract potential adjustments had been made. If you take 200 grams away from grain 1 (pale malt) and add those 200 grams to grain 3 (dex), grain 2 will not have changed at all on the right hand side in weight or percentage. So, all is good. In other words, all the grains do not change, only two of them.

However, if the two grains did not have the same extract potential, the BIABacus would make the right calculations so as your desired Original Gravity would be achieved.

Doing the above in BeerSmith, if the two grains had the same extract potential the end result would be the same. If they didn't, BeerSmith would change the resulting Original Gravity. This means that you would have to play a game of twenty questions (or, more practically, do a gravity scaling) to get the program reading you the right weights). No biggie really as long as you know how to do it in the program you are using.

In fact, the game of twenty questions has to be played in at least some scenarios in any brewing software. The BIABacus minimises the game-playing as the most practical scenario is always given priority. Most users would never have to play the game in the BIABacus.

All other programs require the twenty questions game to be played on at least one aspect of every single recipe that is being copied....

Try this in any existing software (maybe there is an exception?)... If the hop you are using does not have the same AA% as the one in the original recipe, you will need to grab a pen, write down the IBU contribution of that particular hop addition, create your 'new' hop and then enter various weights, over and over (the game of twenty questions), until the IBU's of that particular hop equal what you wrote down . For the hops that contribute no IBU's, things become harder. You actually have to do all of those ones manually to scale them correctly.

As mentioned above, playing the game of twenty questions in the BIABacus is rare. If you find yourself doing it, you probably shouldn't be .

Priming/Odd Stuff

I can't believe that all the above has been written because my main focus/thinking since reading your last post was on your priming question.

Initially I had a simple answer... "Tell Simon, 'One thing I should have said in a much earlier post is that priming sugar should not be entered into the fermentables bill of any brewing software.'"

That's a fair statement but then I thought, "What if Simon asks, 'Why?'"

I couldn't come up with a neat, concise answer for that - something didn't sit right.

[Excuse the following ramblings/stream of consciousness...]

But, then I thought back to some other posts (mally's I think) that also looked at priming and I thought, we can fix this, and then I thought, where can we create the space in the BIABacus for that?, then I found it, then I realised we needed a warning, couldn't find a space for that (and still haven't) and then I realised, just when I thought we had found every single terminology shortfall and solution there was in brewing, so many, there is one more...

Leave that one with us for now but until further notice, stop putting your priming sugar in the main grain bill.


PP

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Hi Simon,

In the attached file, I have altered the weights for percentages and rounded them up for simplicity just to show how it can be done.
I have also added the EOBV-A value (this I had to guess from your info so take it with a pinch of salt), but this will need to be worked out correctly when you come to do your hop additions.

BIABacus PR1.3 - PTY percentage change.xls

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[Quick Edit here Simon: Can you call your priming sugar 'Corn Sugar' (Dextrose) and your specialty grain 'Cara-Pils' (Dexrtrine). The 'Dex' abbreviation is really doing my head in!!!!!!]

Nice work mally and good questions Simon.

Let's get the easy one out of the way first. The BIABacus, at this stage of development, will not give you an accurate Gravity into Boil if you are adding extracts or sugars during the boil. It should however throw you a warning that says...

Gravities above assume all fermentables have been added.

[NOTE: There is a bug I now see but shouldn't affect you Simon. Some stuff has been moved around and so this warning does not currently work if a sugar has been used as the first or second fermnentable. Will fix in PR 1.3K].

Putting a warning there is the best we can do for now. Bear in mind that the BIABacus never originally intended to deal with with a recipe that was not all-grain and never intended to be such a mammoth unpaid project .

So, if you add sugars or extract during the boil and really want to know a gravity into boil estimate (not an important number) then you 'll need to do some calculations on your own or with help here.)

...

Re your point about the two malts having different fermentabilities/extract potentials and someone telling you to increase the Dex contribution from 5 to 7.5% and reduce the base malt accordingly, this is a good question.

Before we go there, the first thing is not to be too pedantic about these things. For a start, BeerSmith won't calculate this (or a gravity into boil figure) for you properly as it ignores the Moisture Content of the fermentable. Straight away you are off by usually at least four percent, often higher.

But let's forget that and focus on the BIABacus. The way you would play the scenario you are talking about is that you would write down the weight of one of the specialty grains. You would then increase the dex to 7.5% (we assume the guy instructing you means weight) and then you would play the game of twenty questions with your base malt until the specialty grain read the amount it did previously.

As I said before, there is always some scenario where you have to play twenty questions. In most software you have to play it on almost every recipe. In the BIABacus you don't, which is nice.

Good question though and thanks Simon - I'd never thought of that particular scenario before. It is also a bit of a pedantic one (not criticising here - I'll come back to this.) And thanks a heap to mally too . His posts above saved me a heap of time. I would have thought/written exactly what he wrote to get to the stage of writing the above. In fact, I actually started writing this post, re-stating everything mally wrote but in a different way and then saw the hole that we had both missed.

...

Pedantic versus Practical: In the past here, we have had a few threads going that ask, "Are numbers really that important?"

They are and they aren't. Numbers, terminology, design, essays like this?/posts like mally's, are components that can accelerate your success as a brewer. On this site, we are trying to put that all together.

People like myself, mally and a few otheres are very good at exploring numbers, terminology and design. Identifying and correcting faults in these areas is very important and, rest-assured, no one else is doing it. Getting things like numbers, terminology and design right will make a massive difference I hope to the hobby and even the industry and I hope BIABrewer gets recognised for all that hard work but...

At the end of the day though, what I think brewers like myself want to see is that newer brewers will more rapidly see how easy all-grain brewing is. You can make a major stuff-up and still get brilliant beer. A gold medal winning beer does not get a gold medal because it had a gravity into boil of 1.060 versus 1.058 - it could have even got the gold because the beer before that one was awful - any judge will tell you that.

The only real/valuable point of numbers should be to make the brewer feel confident that they haven't done anything terribly wrong.

Really, that's all numbers should be used for*.

I also want to cut this post here because I want to get back to the problem encountered at the end of my last post here.


PP

*On this site and for any of us working on the BIABAcus, I think we have a healthy disregard for numbers but also realise how important it is to make the numbers we give others as accurate as possible. A 4% error here along with another 4% error there plus a ten percent variance due to terminology etc quickly sends things beyond a joke which is the current status quo in my opinion.

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This post follows on from my second last post in this thread.

So Simon, we are back to the bit about you including 'Corn Sugar (Dextrose)' in the main ingredient table of your BeerSmith recipe. Remember that and how many things we have covered in between .

And it has been a great thread. It has come up with a whole new philosophical/design question I had never considered. And a whole lot of problems but we are used to solving those .

Original Gravity versus Alcohol Content.

Just when I though we had solved every bloody design, formula and terminology error there was, Simon pops up with a repeat of mally's question a few months ago. The questions are all about priming sugar etc, etc. Very good question. Asked once, I acknowledged that it was a good question but not a high priority. Asked twice and I got thinking. Wish I didn't .

Here's the big problem and I didn't see it until writing the end bit of my second last post here. The big problem here, once again, is caused by existing terminology and culture...

1. Existing culture has the primary focus placed on the Original Gravity of the recipe whereas it really should be on the Alcohol by Volume..

2. Priming sugar does not change the Original Gravity of a beer (that's my logical reason for why you shouldn't put it into the ingredients Simon ) but it will change your Alcohol by Volume by around 0.25 to 0.5%.

mally first brought this issue up here when he asked, "Have you considered adding the gravity/alcohol addition to the BIABacus that occurs during priming?."

Well we now know that we can't add anything to a, 'gravity addition' because there isn't any gravity terminology that currently exists to describe, 'Final Gravity (FG)' plus the gravity added by your priming sugar. What would we call that? Maybe, 'Final Gravity but because I am priming I would like to call it FG and a bit (FGAAB)' and then later call my final, final gravity, my real final gravity (RFG)."

FFS . The above is why I got such a shock at the end of my second last post here. We can solve the maths with a few hours work but I can't see any brilliant way of solving the terminology.

But, the big question is, should you design your beer around an OG or an ABV? (It's a bit like designing the volume around 'Volume into Fermentor (VIF)' versus 'Volume into Packaging (VIP)'.

We haven't asked this question before so if anyone has the energy to start a new thread on this, feel free to go for it. Personally I think the answers are obvious - all recipes should be based on 'Volume into Packaging (VIP)' and 'Alcohol by Volume (ABV)'. The reality though is that the BIABacus is the first tool that could even allow such thinking/accuraccy to possibly exist.

PP

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Ha ha . In all those posts above, I had assumed Simon that the 950 grams of dextrose was your priming sugar. That would be a lot of priming sugar eh? . Anyway, at least we solved the number discrepancy.

A couple of loose ends...

... A few posts ago you asked about the accuracy of the BIABacus auto-efficiency estimate. Basically a lower OG beer will always have higher kettle efficiency than a high OG beer - not sure if you had gathered that bit yet. Anyway, the auto-efficiency seems to be working well. We've set it slightly low. In other words, a brewer with good procedures and water should score a little higher than the estimate. Setting it a bit low is the best place for the default.

... In the post above, you mentioned how you can use BeerSmith to work out your gravity with sugars added during the boil. There are two errors here. Firstly there is the 4% volume error on the volume going into the boil. Secondly, there is a further error in that BeerSmith does not currently consider the moisture content of the fermentable. This can be very significant. (Alter the moisture content of one of your grains and you'll see that nothing changes in the gravity predictions.)

... Taking a gravity reading at the start of the boil is helpful as it gives you a first 'kettle efficiency' check. You can take a set of gravity and volume readings at any time during the boil and, assuming you have added no more fermentables, the resulting efficiency reading should be the same.

You'll often read about brewers taking pre-boil gravity readings and adjusting things based on that one reading. I am very opposed to this as a single reading can be very inaccurate. In other words, people can end up making an adjustment that actually wasn't needed. It is also impossible to predict evaporation perfectly on a brew day so any pre-boil corrections may have to be re-corrected again post-boil.

If I take a pre-boil gravity and volume reading, it is only for the purpose of it being the first of two checks on my kettle efficiency. It would be nice though for you to be able to get a proper estimate that discounts sugar additions during the boil so you could have this double check as well. Looks like the BIABacus or BeerSmith isn't going to do it for you atm .

... Finally, very nice job on the competition Simon

• • SVA Brewer With Over 100 Brews From Australia
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