[Kaiser]

I've noticed that White Labs is also marketing their lab tests to home brewers. But how valuable do you think they are?

$36 to have alcohol tested is pretty low value in my opinion. Alcohol is fairly well determined by OG and FG readings and we don't need an exact value anyway. Maybe useful for bragging rights if you were going for a high alcohol brew.

IBU measurements might be useful for bragging rights and diacetyl and bacteria for getting to the bottom of a persistent issue. But all these tests are rather expensive for the common home brewing budget.

Kai

[Jimmy K]

$36 for single use? That would be a specialty homebrew product in my opinion. Bragging rights for a high gravity brew would be the only reason I'd think to use it. A hydrometer can overestimate that.

[Jimmy K]

Or to measure after some goofball procedure, such as freeze distillation. (Nobody does that, though. It's illegal). 

[Kaiser]

Or to measure after some goofball procedure, such as freeze distillation. (Nobody does that, though. It's illegal). 

I forgot about that. That would be useful in that case.

Kai

[a10t2]

Or to measure after some goofball procedure, such as freeze distillation. (Nobody does that, though. It's illegal). 

Freeze distillation as in making eisbier? That's legal.

I brewed a beer a few years ago that would be about 23% ABV based on SG readings. If the remaining bottles weren't so precious at this point I could see myself spending $36 to see where it actually ended up.

When I go for 30% next year I'll probably order the test.

[a10t2]

Oh, and White Labs' normal QC program is $139 for the full panel of tests on two beers. I don't know if there's a point at which that becomes less expensive than the piecemeal tests.

[svejk]

Freeze distillation as in making eisbier? That's legal.

This is true - a while back, James Spencer from Basic Brewing Radio spoke directly with the TTB about this and was told that since freezing is not a form of distillation and as long as there isn't an intent to sell, it isn't illegal.

[Jimmy K]

Freeze distillation as in making eisbier? That's legal.

This is true - a while back, James Spencer from Basic Brewing Radio spoke directly with the TTB about this and was told that since freezing is not a form of distillation and as long as there isn't an intent to sell, it isn't illegal.

What ... nobody asked ATF? Almost zero chance of getting caught anyway since there is no specialized equipment. I thought the law said any means of separation.

[Jimmy K]

I brewed a beer a few years ago that would be about 23% ABV based on SG readings. If the remaining bottles weren't so precious at this point I could see myself spending $36 to see where it actually ended up.

When I go for 30% next year I'll probably order the test.

Let us know who that works out! The SG of ethanol is about 0.80, so it will cause an overestimate. But by my calculation, even at 25% it would only through off the reading by <1%ABV.

[a10t2]

What ... nobody asked ATF?

It'd be interesting to hear what they had to say. There's a definite possibility they'd tell you to talk to the regulatory agency (TTB). Sort of like calling the police to ask if it's legal for you to build a shed in your yard.

Let us know who that works out! The SG of ethanol is about 0.80, so it will cause an overestimate. But by my calculation, even at 25% it would only through off the reading by <1%ABV.

I definitely will. It should be quite the project.

I'd assume that all the ABV estimates out there already take into account the ethanol's impact on SG. For example, a beer fermented from 1.050 to 1.010 would be 5.0-5.2% ABV depending on what equation you use. If you assume that the entire drop in gravity is due to sugars fermented you'd get about 6.7% ABV.

[Kaiser]

I'd assume that all the ABV estimates out there already take into account the ethanol's impact on SG.

They do but if you are working with sg and use the ABV formula, you make a linear assumption between extract content and sg. The higher the gravity the further you are actually deviating from this assumption. I don't know what brewing calculators are doing, if they convert sg to Plato before the ABV calculation or if they are using gravity points to calculate ABV. The latter would be less precise.

Kai

[Jimmy K]

They do but if you are working with sg and use the ABV formula, you make a linear assumption between extract content and sg. The higher the gravity the further you are actually deviating from this assumption. I don't know what brewing calculators are doing, if they convert sg to Plato before the ABV calculation or if they are using gravity points to calculate ABV. The latter would be less precise.

Kai

Is the plato formula better? Because just converting units shouldn't make it any more precise.

[a10t2]

Is the plato formula better? Because just converting units shouldn't make it any more precise.

"Better" is kind of a loaded word. What Kai's saying is that when using (apparent) attenuation to estimate alcohol content, working in degrees Plato will give a more accurate result, because the units scale linearly with sugar content, by definition. SG, on the other hand, scales as a function of density.

So, for example, a 20°P wort contains twice as much sugar per unit volume as a 10°P wort. A 1.080 wort contains about 1.93 times as much sugar per unit volume as a 1.040 wort.

[Jimmy K]

Is the plato formula better? Because just converting units shouldn't make it any more precise.

"Better" is kind of a loaded word. What Kai's saying is that when using (apparent) attenuation to estimate alcohol content, working in degrees Plato will give a more accurate result, because the units scale linearly with sugar content, by definition. SG, on the other hand, scales as a function of density.

So, for example, a 20°P wort contains twice as much sugar per unit volume as a 10°P wort. A 1.080 wort contains about 1.93 times as much sugar per unit volume as a 1.040 wort.

That makes sense, but wouldn't that only apply if you measure sugar directly? If you convert gravity to plato you're still constrained by the limits of the measurement method.
 
And I had no idea about that last sentence. I would have thought sugar content would double.

[Kaiser]

Many of the home brew calculations choose simplicity over accuracy and that's not a problem if you are simply comparing batch to batch or communicate with brewers that use the same calculations. But if you want to know the exact number you may have to abandon the simple methods.

For all practical purposes the accuracy limiter in most cases will be the accuracy of the hydrometer readings.

Large commercial brewers care a lot about precise measurements since they matter for both taxation and they don't want to spend more grain than they really need.

Kai