Considerations when predicting the final gravity.

It seems that not a lot of people care to hit their estimated final gravity. Many state "you can't predict the yeast behavior" or " there are too many unknown variables that affect final gravity to include this in a tool", so people usually just accept what the brewing tools predicts. These tools ignore the fact that not all sugars are fermentables and apply the yeast attenuation suggested by the manufacturer to the whole amount of sugars.

Can you brew successfully that way? Yes you can, but hitting the required final gravity when you are trying to brew a specific style takes time and multiple batches until you make the needed adjustments.

So I decided to look at the behavior of one yeast strain that I use a lot, Wyeast 1056 American Ale, using empirical data recorded from several batches in order to come up with a better way when predicting the final gravity.
The analysis included all grain recipes with variable grain bills for multiple styles, from light beers up to brown ales, all using Wyeast 1056.
When looking at the graph of mashing temp against final gravity, there was a visible relationship, already known by most people.
It also shown that the suggested attenuation from the manufacture was quite off.
The graph below shows the mashing temperature in the bottom and the related attenuation on the top. The flat lines are the suggested maximum and minimum yeast attenuation. Fermentation temperatures were within the suggested range for this yeast, from 60 to 72F.

From this graph, it is clear that the higher the mashing temperature, the lower the attenuation, as expected. Based on that and using the available data points, I came up with the following function:

Attenuation%=50+800/(T-130) (for T from 150 to 160F)

where T=mashing temperature

Now, using this function, the graph below shows the predicted attenuation in red for the same batches. It would represented much better the real measured data than by just using the suggested range of 73 to 77%, which again, is way off.

It is known that many other factors affect the final gravity, but since mashing temperature seems to be an important one, using this simple function can improve the accuracy when predicting FG.

The actual graph for the function is shown below.

Another step that also help improving accuracy when estimating the FG is to exclude the dextrin sugars and other known non-fermentables from been attenuated, like carapills malt and lactose, usually added to increase head retention and body of the beer.
My basic excel calculation file do just that, by letting the user assign the estimated fermentables for each grain or adjunt.

Brewing a Dunkelweizen

First time brewing this style. A wheat beer with some malty notes sounds delicious!

Here's the recipe. Brewed it today and it is right now at 70F in my fermentation chamber. Will lower to 62F once fermentation has started.

• 5.5# Weyerman Wheat Malt




• 3# Munich Malt




• 0.5# Cara-Munich Malt - Belgian




• 3oz Weyerman Carafa Special II




• Wyeast 3098




• 1oz Hallertau 4% hops for 60min

Mashed at 155F for 60min. OG at 1.044, which was lower than my target of 1.051 but still within the range for this style. Mashing efficiency at 65% instead of estimated 75%, possibly due to the large amount of wheat malt used.

Click HERE to see the review of this batch.

Carbonation test

My first batch of beer was a partial mash extract recipe and one thing I wonder was how much of those priming sugar drops I should use on a 22oz bottle to properly carbonate the beer. I also wondered how much pressure would be building up inside the bottles and creating bottle bombs was a concern.

So I decided to do a simple test by using a plastic bottle with a psi gauge attached to the cap to measure the pressure for the recommended 3g of sugar per bottle. Also tested 6g per bottle to see what impact that would have on the pressure.

Here are the photos of the setup

The results were a little surprising. The bottle with 3g of sugar had a pressure actually higher than the one with 6g of sugar. But after about 10 days, I decided to shake the bottles a bit since I was wondering if the sugars were just sitting to the bottom and not really well mixed into the beer. It seems the CO2 was dissolved in the beer and once shake, the pressure on the bottle with 6g of sugar became higher. Later, both bottle were set into the fridge and pressure on both dropped, as expected. The maximum pressure registered was 36PSI for the 6g bottle and 30 PSI for 3g of sugar. Those same amounts of sugar was also used for regular 22oz glass bottles. So as a result of this test, I figured that 36PSI is not enough to turn the bottles into bombs and I could compare what carbonation levels 3g and 6g of priming sugar would create.

Here's a graph of the results.

Brewing a Belgian Wit

Belgian wit is a very refreshing beer with lots of wheat malt and spices and is one of my favorites.

Here is a recipe I have brewed few times that I recommend:

• 5# Belgian pilsner malt 1.5L



• 3# wheat malt 1.8L



• 1/2# Briess aromatic



• 2# Flaked wheat



• 1/4# flaked oats



• 1# rice hulls



• Wyeast 3944 Belgian wit



• 1/2oz Kent golding for 60min



• 1/2oz Kent golding for 30min



• 1/2oz Kent golding for 10min



• 1 tsp Irish moss for 20min



• 1/2oz sweet orange peels



• 1/2oz bitter orange peels



• 1/4oz cracked coriander



• 1g cracked paradise seeds

The spices were added to the boil for last 10min inside a muslin bag. The numbers for this batch were:

OG=1.050

FG=1.008

ABV=5.4%

Color=6

IBU=18

Mashing temp was 154F and fermentation temp 62F. It took 10 days to reach FG. Here's the graph of the fermentation profile. Click on the image to see it larger.

And here it is, ready to drink.

Brewing a malzbier

Malzibier is also known as an energy drink and is a a low alcoholic beer, very sweet and dark. It is achieved in commercial scale by pitching the yeast in the wort at very low temperatures, close to 32F. That process slow down the yeast activity so after few days, most of the sugars are still there, then it is pasteurized and forced carbonated for bottling.

Malzbier is very common in some countries, specially in Brazil and it is very different from what is called "Malta". I have tried Malta recently for the first time to check if it would be like malzbier but it was very disappointing. Malta is pretty much a sweet wort, sorry for those that like it, but it just doesn't taste like beer at all. I tried few different brands and all were almost the same, sweet wort with lots of molasses. Not good!

Back to what a malzbier should taste like, it definitely taste like beer, it is sweet but not as much as Malta.

I finally decided to give it a shot and brew something like it, a low alcohol beer with strong coffee taste and sweetness. The problem with homebrewing that is the required pasteurization process, so I decided to brew it using a low fermentable wort by adding lots of dextrin malt and lactose.

My plan was to have most of the sugars left after fermentation, so here's is my recipe:

• 1# crystal 120L


• 1# crystal 40L


• 1# chocolate 350L


• 1# briess aromatic


• 3# Carapils


• 2# Lactose


• 1/2oz Horizon 13% for 60min


• 1/2oz Hallertau 6% for 30min


• 1/2oz Hallertau 6% for 10min


• 1 tsp irish moss for 20min


• OG=1.040/FG=1.030/Color=28/IBU=40/ABV=1%


• Mashing temp=153F/Yeast=1084/Boil volume=6.5gals


• Fermentation temp=70F

It has been couple of weeks in the bottles and it is still developing flavors but it taste a little different than what I recall from having a malzbier. It has a much stronger coffee flavor and despite the FG at 1.030, it doesn't taste that sweet at all. If I ever attempt this type of beer again, I may reduce the chocolate malt and add some chocolate nibs or other chocolate flavoring adjunct.

But the outcome was not that bad. It taste like beer, like a strong and sweeter brown ale.

UPDATE: Left a bottle of this brew sitting in my fridge for 18 month. Check the review of that bottle HERE.

Buying hops online

I just received a batch of hops that I purchased online from hopsdirect.com. It is so much cheaper to buy hops online, than from my LHBS. The minimum order is a pound and the price is something like 1/5 of my LHBS, so I a got total of 4#, divided in Centennial, Crystal, Hallertau and Goldings. I then used my foodsaver machine to vacuum pack in 1oz bags, then into the freezer. I should have hops for a year of brewing, for only $50. What about that? By the time I run out of hops, I should be harvesting my own hops that may yield over 3# next year.

Brewing with consistency

Brewing the same batch twice and keep consistency on the final product is one of the most challenging things on home brewing. Keep track of most variables is the best way to achieve that. Some of the things to look at when trying to keep consistency are:

1. Availability of ingredients - When we go to our LHBS with our recipe, sometimes we can't find the exact grain or hops we are looking for, so we end up having to replace those with whatever is the closest available compromising the outcome and your attempt to brew that batch that you liked. One way to avoid that is to stock some vital grains and hops so you make sure you use the right ingredients. Liquid yeast however is better to buy as you brew so you can get the fresher possible. Dry yeast can be stored for several month with no problems.


2. Temperature control - Keeping fermentation temperatures under control is a very important step to re-create the same beer profile twice. That's when a fermentation chamber comes very handy. Many home brewers convert their chest freezers into fermentation chambers by replacing the thermostat, some other folks add a temperature controller. This approach seems to be very popular and can also work when brewing Lagers, which requires lower temperatures. My personal approach when I start thinking to build a fermentation chamber was that I would like to both heat and cool by carboy automatically, so it would allow me to brew either during summer, when temperatures reach 100F, and during winter with 15F outside. Some photos of my fermentation camber can be found HERE.
3. Recording the variables - It is important to keep track of as many variables as possible in order to allow you to re-do a batch. Here's a list of the variables that I currently keep track on all my batches.

• Detailed description of all ingredients, including name, brand, quantity, time in which it was added to the brewing process


• Temperatures of the strike water, ambient, sparge water, initial and final mashing temperatures, mashing time, boil time, time of additions to the boil.


• Measurements of the wort gravity when starting the sparge, end of sparge, pre-boil and final original gravity of the wort before pitching the yeast. Calculated mashing and brew house efficiency.


• Fermentation temperatures, daily measurements of gravity during fermentation, which I use to build a chart of gravity x days. That's allows me to track the fermentation profile and identify possible issues even before it happens, like a stuck fermentation, which can be avoided if temperature is increased to keep the yeast working. Finally, track of the final gravity and calculated alcohol by volume, color and IBU's.

Below is an example of gravity chart for multiple batches. Gravity was taken daily. The green curve is for a Whitelabs 001 while all the others curves are for Wyeast 1056. All gray curvers are partial mash extract batches while the red and blue are all grain batches. Playing with fermentation temperatures, addition of dextrin malt and other changes are very visible when a chart like this is available. It gives me the ability to better predict the outcome of a batch just by looking the behavior on the first days of fermentation.