Created a short summary of my brewing literature here. Enjoy.
Refractometer Revisited
March 1st, 2012 § 2 Comments
I took another look at my assessment of the refractometer and have a few clarifications and corrections. I revisted the BYO article referenced in the post and noticed the “slightly more accurate” formula for converting Brix to specific gravity:
SG = 1.000019 + (0.003865613 × Brix + 0.00001296425 × Brix + 0.00000005701128 × Brix)
This proves to be the formula used for the refractometer’s dual scale. The values line up from top to bottom. As noted in the article, this formula has no correctional value applied for wort. To further confirm that no correctional values have been applied to the instrument, I tested a few samples of pure water/sucrose (table sugar) solution at various concentrations. The Brix scale was accurate for every sample.
So while the refractometer’s Brix scale is accurate, the specific gravity scale is not at all due to the fact that the equation is wrong. As Sean Terrill noted recently the formula appears to be “a cubic and that the exponentials didn’t copy-paste properly.” Sure enough, the original formula is:
SG = 1.000019 + (0.003865613 × Plato + 0.00001296425 × Plato2 + 0.00000005701128 × Plato3)
Source: Siebert, K.J., Routine Use of a Programmable Calculator for Computing Alcohol, Real extract, Original Gravity & Calories in Beer, ASBC Journal, Vol.38, No. 1, p. 27 (1980).
The conversion formula I used earlier is from A Textbook of Brewing by Jean De Clerck. Although both equations are intended to convert °Plato they can be used for °Brix for all practical purposes in brewing. You can see in the graph below that the corrected version of Siebert’s equation matches De Clerck’s.
This better explains the discrepancy I perceived between the refractometer’s two scales. Whereas I said earlier “the corresponding specific gravity reading to 25°Bx should be 1.101″ it really would be 1.106 using either of the valid formulas but does in fact read 1.097 using the incorrect version of Siebert’s.
Now that is has been established that the refractometer does not apply any correctional value for wort — and inaccurately labels it as such — a correctional value still needs to be applied to the °Brix reading before converting to specific gravity using either of the correct equations.
Starting a Starter
November 25th, 2011 § No Comments
I begin my yeast starter by boiling 1,000 mL of wort in a 2,000 mL Erlenmeyer flask which 80% of the time boils over. I got tired of having to stand guard over it and cleaning the stove from the times I do walk away so I changed the process a bit. I now boil the wort in a small pot large enough to avoid boil-overs. Simultaneously I will boil water in the flask to sanitize and heat it up. When both are ready I dump the water and pour the wort into the flask. Sure, I now have a pot to clean but it beats cleaning a sticky stove.
Pumpkin: Round 3
October 6th, 2011 § No Comments
They’re here! I finally found sugar pumpkins at Whole Foods this week. I am attempting to start a culture from the dregs of a pale ale (WLP001) brewed this past June for this year’s batch of pumpkin ale.
Bottle Rinser
September 22nd, 2011 § No Comments
I purchased a Vinator Bottle Rinser to help speed things up on bottling day. All I can think about is why did I not do this earlier. Seriously, forget about the sanitization cycle on your dishwasher and baking bottles in the oven. Save the energy and time and pick one of these up along with some Star San. Give each clean bottle a few squirts and you are ready to package.
Fear Not the Foam!
Priming with Yeast
September 22nd, 2011 § No Comments
I decided to prime my Vienna Lager with fresh yeast (along with priming sugar) given that it had been lagering near freezing for six weeks. Instead of buying a fresh vial I made a 100 ml culture using the yeast I gathered from washing the yeast cake before lagering. It took right off so needless to say I am a fan of yeast washing. Hopefully it is a large enough culture for the 2.5 gallons I bottled.
Decoction
September 7th, 2011 § No Comments
Boiling grain? What's up with that!?
I brewed a Dortmunder following an enhanced double decoction mash schedule. The usual response given when asked in the homebrewing community if a decoction mash is worth the effort is “try it yourself.” It certainly made for a long and busy brew day but it was an exciting challenge. I will hold any judgements on its value until I have tasted the beer.
Here are a few pieces of advice I will offer to anyone who is willing to give it a go:
- Watch Kai’s videos (here, here, and here) and take notes. Have your calculations prepared ahead of time.
- Consider trying a small batch. The mash schedule was certainly long, but it would have been much longer had the decoctions been larger.
- Watch the Acid Rest temperature. It’s closer to room temperature than you think. Thankfully I only overshot my strike water.
- The first decoction pull is large. Don’t be shy. Dig in.
- Check the decoction for conversion before adding it back to the main mash.
- Have some additional water nearby to add to the decoction as it dries out.
My biggest bewilderment was the decoction size. Neither pulls were large enough to raise the main mash to the next step. I understand they need to be thick but perhaps mine were too thick. Thankfully I had my heatstick to help out.
Dortmund Water
September 3rd, 2011 § No Comments
I am considering to brew a Dortmunder which is one of those styles having a flavor attributed to a regional water supply. Dortmund’s water is known to be rich in minerals. Its profile can be found in a number of brewing resources including How to Brew. I began experimenting with various salt additions using my city’s recent water report and Kai’s Water and Mash pH Spreadsheet to see if I could approach this profile without having to default to distilled or reverse osmosis water as a base. I think I am certainly on track:
| Calcium (Ca+2) |
Magnesium (Mg+2) |
Bicarbonate (HCO3-1) |
SO4-2 | Na+1 | Cl-1 | |
|---|---|---|---|---|---|---|
| Dortmund | 225 | 40 | 220 | 120 | 60 | 60 | Post-Additions | 97 | 20 | 220 | 120 | 21 | 61 | Preferred Range | 50-150 | 10-30 | 0-50 (pale) | 0-350 | 0-150 | 0-250 |
The first noticeable outlier to address is Magnesium. Magnesium serves a similar purpose as calcium in brewing water but is less beneficial. The only salt I have available to raise magnesium is epsom which also raises sulfate. I therefore intentionally kept it in the center of the preferred range so that I could utilize more gypsum to increase the calcium – which also increases sulfate.
Sodium, which is also quite low, could be increased with either table salt or baking soda but that would also increase the chloride and bicarbonate levels respectively which currently are on target.
Calcium is quite low in comparison to the Dortmund level but again any further salt additions would raise other ion levels beyond their respective targets. I know that calcium is instrumental for useful reactions occurring in the mash and in the boil but I am unaware of the difference in flavor this lower amount would or would not impart. I will rest knowing 97 ppm is acceptable as it is within the preferred range.
Sulfate, bicarbonate, and chloride each came right in on their mark. These are what contribute towards the water’s mineral taste according to the BJCP guidelines.
At the end of the day however it is the mash and boil pH that matters. The spreadsheet predicts that the mash pH will be 5.7 (room temperature) which is close to the upper acceptable limits. Lactic acid can be used to bring it down.
UPDATE: The mash pH started around 5.2 at dough-in which was quite low. I added enough baking soda to increase the level of sodium to that of the Dortmund profile to drive up the carbonate level. It raised the mash pH to around 5.6.
Yeast Washing
August 17th, 2011 § 3 Comments
One of the first things I learned while preparing for my first lager (a Vienna) is the recommendation to pitch fresh yeast for bottle conditioning. It sounded like a good opportunity to try yeast washing.
Yeast washing is the process of extracting fresh yeast from a yeast cake ideally after primary fermentation. This video and article from BillyBrew are great resources. Here are a few snapshots from when I washed the White Labs WLP820 yeast cake.
The beer is racked after primary and sanitized water has been added to the carboy.
About half gallon of the “good stuff” is poured off into a small jug and allowed to settle.
Three 6-oz. mason jars are filled with viable yeast and ready to be placed in the refrigerator.
The yeast has settled after about a week. It certainly doesn’t appear to be a large amount. I’ll either need to try to pour more of the creamy layer or use larger jars on the next attempt. All three jars together have enough though to start a good culture for priming.
Refractometer
July 23rd, 2011 § 3 Comments
My latest goal is to see if I can get a better reading on my mash efficiency so that I can adjust my recipes accordingly. A refractometer will be useful here and thanks to recent research by Sean Terrill it also may be used to measure final gravity with respectable accuracy.
Here’s a summarization of things I learned using my newest gadget:
Don’t trust the specific gravity scale.
Apparently most if not all refractometers that come with a specific gravity scale are not accurate. The corresponding specific gravity reading to 25°Bx should be 1.101. As you can see mine is not accurate.
Brix isn’t entirely accurate either, but it’s close.
Refractometers are designed to measure the percentage of sugar in a pure sucrose solution, which wort is not. A correction value needs to be applied. Read the BYO article for complete details but 1.04 is considered the standard.
Brixf = Brixi / 1.04
Now you can convert Brix to specific gravity using the following formula:
specific gravity = Brixf / (258.6 − ((Brixf / 258.2) × 227.1)) + 1
Want to try final gravity? There’s a formula for that.
A refractometer has been considered useless in the past for measuring the final gravity of a fermented beer as alcohol skews the readings. Sean Terrill has provided a working formula from his and others’ research and experiments to compensate for this:
specfic gravityfinal = 1 − 0.00085683 × Brixoriginal + 0.0034941 × Brixfinal
Note: Don’t forget to apply the correction value to your Brix readings.