Mill Gap for BIAB (Efficiency Problems)

[dmtaylor]

Why is it rusty?

4 Fe + 3 O2 ---> 2 Fe2O3

 

[Epos7]

Why is it rusty?

They must have spent some time in a humid environment before or during shipment. I was able to get them looking pretty nice using a stainless steel brush. Then I scrubbed them in some soapy water to remove all the dust, rinsed, and immediately placed them in a hot oven to prevent further rusting. I might apply a really light coat of mineral oil for added protection.

 

[stever1000]

4 Fe + 3 O2 ---> 2 Fe2O3

Clever

 

[dmtaylor]

Clever

Not as clever as stever.

 

[Epos7]

I was able to brew for the first time using the new knurled rollers on my mill yesterday. One observation is that the knurled rollers are slightly wider in diameter than the helical rollers, though both are specified as 2". The practical implication is that while I couldn't set the mill gap with the helical rollers below 0.022", I can now set the mill gap all the way down to 0. I found that most people are setting their mills with knurled rollers at a gap around 0.035" so I set my mill to 0.030" as I don't have to deal with stuck sparges doing BIAB. The knurled rollers set to a 0.030" gap produced a crush that was noticeably finer than what I was seeing with the helical rollers set to a gap of 0.022".

It was cold yesterday, and though I wrapped the kettle in a sleeping bag, I found the mash was losing about 1.5 degrees F per 15 minutes, so I turned the burner back on at 15, 30, and 45 minutes to bring the mash temperature back to my target 152F. The result is that the mash temperature fluctuated from 150.2F to 152F for 60 minutes. An added benefit was that the mash received a couple of minutes worth of stirring every 15 minutes.

I checked the volume markings on my kettle earlier this week and found that they are off by ~0.3 gallons. I accounted for this and am now confident my measured volumes are accurate to < 0.1 gallon.

I chose to brew the Mosaic Honey Wheat recipe for the third time, to see if I could produce any efficiency gains over my previous attempts with the helical cutters.

9 pound total grain bill (4.082kg)

4 pounds Great Western organic 2 row
4 pounds Great Western organic white wheat
1 pound Gambrinus honey malt

Mashed in 7.37 gallons of RO water with the following additions:

4.5g gypsum
4g calcium chloride (4.3g measured to account for hygroscopic nature)
2g baking soda
4mL 88% lactic acid

I heated my strike water to 157.3F, mashed in, started my timer, then stirred for a couple of minutes before closing and insulating the kettle. Where possible, I tried to take measurements with both my Milwaukee MA871 refractometer and a 9-21 brix precision hydrometer. All samples were covered and chilled to 20C prior to measurement.

15 minutes into mash:

temp - 150.5F
pH - 5.21
refractometer - 4.1

30 minutes into mash:

temp - 150.4F
pH - 5.29
refractometer - 6.0

45 minutes into mash:

temp - 150.2F
pH - 5.38
refractometer - 8.3

60 minutes (mash end):

temp - 150.7F
pH - 5.39
refractometer - 9.1
hydrometer - 9.3

After removing and squeezing the bag:

volume - 6.6 gallons
refractometer - 9.5
hydrometer - 9.8


With the new knurled rollers, I was hoping to see a better crush, improved conversion efficiency, and faster conversion (was hoping conversion would be mostly complete by 30 minutes). I did see the improved crush, and slightly improved conversion efficiency. I did not see the conversion process complete by 30 minutes, and to my disappointment the SG was higher after squeezing the bag than it was at the 60 minute mark, likely meaning that conversion had not completed.

Putting the formulas here to use, I came up with the following conversion efficiencies:

60 minutes:
refractometer - 85%
hydrometer - 87.6%

post-squeeze:
refractometer - 89.7%
hydrometer - 92.8%

So if you believe the hydrometer is most accurate, I came close to seeing good conversion after squeezing the bag. As has been discussed previously in the thread however, measured brix/sg should be the same at the end of the mash as it is after squeezing the bag. The fact that it wasn't means conversion was not complete. The mash was stirred thoroughly throughout the 60 minutes, so I can't imagine that is the issue.

I think next time I'll try dropping the mill gap to 0.025" and see what happens, but I'm no longer holding out hope. Something about my system just doesn't like producing good conversion efficiency, and after 4-5 months, 9 batches of beer, a lot of time, effort, and money, I still can't figure out what it is.

 

[doug293cz]

Hey, sounds like you're making good progress, just not quite there yet. I agree with dropping the gap to 0.025" for your next trial. I got ~99% conversion on the last batch I did (60 min mash) with a 0.022" gap (up from 0.016" I had been using) on my two roll mill.

Brew on

 

[wilserbrewer]

I think you need to tighten your mill, quite a bit.
.

Yes agreed, tighten the mill down as Doug suggests.

 

[Epos7]

Good point, maybe I do just need to go tighter. Plenty of adjustment left with the new rollers.

Cheers!

 

[RM-MN]

I was able to brew for the first time using the new knurled rollers on my mill yesterday. One observation is that the knurled rollers are slightly wider in diameter than the helical rollers, though both are specified as 2". The practical implication is that while I couldn't set the mill gap with the helical rollers below 0.022", I can now set the mill gap all the way down to 0. I found that most people are setting their mills with knurled rollers at a gap around 0.035" so I set my mill to 0.030" as I don't have to deal with stuck sparges doing BIAB. The knurled rollers set to a 0.030" gap produced a crush that was noticeably finer than what I was seeing with the helical rollers set to a gap of 0.022".

It was cold yesterday, and though I wrapped the kettle in a sleeping bag, I found the mash was losing about 1.5 degrees F per 15 minutes, so I turned the burner back on at 15, 30, and 45 minutes to bring the mash temperature back to my target 152F. The result is that the mash temperature fluctuated from 150.2F to 152F for 60 minutes. An added benefit was that the mash received a couple of minutes worth of stirring every 15 minutes.

I checked the volume markings on my kettle earlier this week and found that they are off by ~0.3 gallons. I accounted for this and am now confident my measured volumes are accurate to < 0.1 gallon.

I chose to brew the Mosaic Honey Wheat recipe for the third time, to see if I could produce any efficiency gains over my previous attempts with the helical cutters.

9 pound total grain bill (4.082kg)

4 pounds Great Western organic 2 row
4 pounds Great Western organic white wheat
1 pound Gambrinus honey malt

Mashed in 7.37 gallons of RO water with the following additions:

4.5g gypsum
4g calcium chloride (4.3g measured to account for hygroscopic nature)
2g baking soda
4mL 88% lactic acid

I heated my strike water to 157.3F, mashed in, started my timer, then stirred for a couple of minutes before closing and insulating the kettle. Where possible, I tried to take measurements with both my Milwaukee MA871 refractometer and a 9-21 brix precision hydrometer. All samples were covered and chilled to 20C prior to measurement.

15 minutes into mash:

temp - 150.5F
pH - 5.21
refractometer - 4.1

30 minutes into mash:

temp - 150.4F
pH - 5.29
refractometer - 6.0

45 minutes into mash:

temp - 150.2F
pH - 5.38
refractometer - 8.3

60 minutes (mash end):

temp - 150.7F
pH - 5.39
refractometer - 9.1
hydrometer - 9.3

After removing and squeezing the bag:

volume - 6.6 gallons
refractometer - 9.5
hydrometer - 9.8


With the new knurled rollers, I was hoping to see a better crush, improved conversion efficiency, and faster conversion (was hoping conversion would be mostly complete by 30 minutes). I did see the improved crush, and slightly improved conversion efficiency. I did not see the conversion process complete by 30 minutes, and to my disappointment the SG was higher after squeezing the bag than it was at the 60 minute mark, likely meaning that conversion had not completed.

Putting the formulas here to use, I came up with the following conversion efficiencies:

60 minutes:
refractometer - 85%
hydrometer - 87.6%

post-squeeze:
refractometer - 89.7%
hydrometer - 92.8%

So if you believe the hydrometer is most accurate, I came close to seeing good conversion after squeezing the bag. As has been discussed previously in the thread however, measured brix/sg should be the same at the end of the mash as it is after squeezing the bag. The fact that it wasn't means conversion was not complete. The mash was stirred thoroughly throughout the 60 minutes, so I can't imagine that is the issue.

I think next time I'll try dropping the mill gap to 0.025" and see what happens, but I'm no longer holding out hope. Something about my system just doesn't like producing good conversion efficiency, and after 4-5 months, 9 batches of beer, a lot of time, effort, and money, I still can't figure out what it is.

Your conversion was likely done at 30 minutes but when conversion happens the wort is more dense than water and sinks, leaving you with less dense water near the surface. During the rest of the time the sugary wort will disperse into the less dense water making you think that you are still getting conversion. Next batch, stir very well before taking your refractometer sample. I'll bet that your reading will not change from the 30 to 60 minutes if you get the wort mixed well.

On my last batch I took a refractometer sample about 3 minutes into the mash, then another one at 15 minutes and found that the gravity had gone down. I know that with some religions you can unconvert but I doubt that I had unconversion in my mash.

 

[doug293cz]

Your conversion was likely done at 30 minutes but when conversion happens the wort is more dense than water and sinks, leaving you with less dense water near the surface. During the rest of the time the sugary wort will disperse into the less dense water making you think that you are still getting conversion. Next batch, stir very well before taking your refractometer sample. I'll bet that your reading will not change from the 30 to 60 minutes if you get the wort mixed well.

On my last batch I took a refractometer sample about 3 minutes into the mash, then another one at 15 minutes and found that the gravity had gone down. I know that with some religions you can unconvert but I doubt that I had unconversion in my mash.

It's not that there is higher SG wort formed near the top of the mash, that then sinks, it's just that higher SG wort forms lower in the mash. What happens, particularly in a thin mash, is the grain settles towards the bottom of the vessel, so that is where more sugar gets created, and higher SG wort exists, because that's where the starch is. So, the SG stratification is caused by where the sugar is actually formed. And, it takes way more stirring than you think it does to get the wort homogenized. (I got bit by insufficient mixing of initial and sparged wort, leading to an erroneously low pre-boil SG measurement, on my last batch. And I thought I stirred pretty well.)

Brew on

 

[wilserbrewer]

Yes to the above! Also if the wort is stratified with a higher concentration of sugar, the absorbed wort within the grain is also at a higher concentration.

Stirring well twice is a good thing IME.

 

[Epos7]

Cheers guys. I did stir the wort for several minutes at 15 minute intervals throughout the mash. I also raised and lowered the bag when I refired the burner at 15, 30, and 45 minutes to keep it off the bottom of the kettle. The tradeoff with extra stirring is you lose a lot of heat when doing so, but I'll give it a shot!

 

[wilserbrewer]

Glad you are progressing. This thread should be retitled, "Efficiency problems w/ Monster Mill Slotted Helical Rollers"

I'm a little disappointed MM didn't rectify the situation promptly, and yet charged you shipping to sub the rollers on a $400 purchase. doesn't sit well with me....jmo
Cheers!

Ps The Captain Crush went the way of the dinosaur, maybe this will also unless they retool.

 

[njpatg]

Two roller monster mill set at .035 , my efficiency routinely approaches 80%

 

[Epos7]

Glad you are progressing. This thread should be retitled, "Efficiency problems w/ Monster Mill Slotted Helical Rollers"

I'm a little disappointed MM didn't rectify the situation promptly, and yet charged you shipping to sub the rollers on a $400 purchase. doesn't sit well with me....jmo
Cheers!

Ps The Captain Crush went the way of the dinosaur, maybe this will also unless they retool.

I wasn't all that enamored with the service. Despite mentioning it multiple times, they wouldn't acknowledge that their website advertises being able to set the mill gap as low as 0, while I couldn't get it below 0.022" on the slotted rollers.

They did agree to replace the rollers quickly when I asked, but ignored my request for a refund for the difference three times before I finally received one. It wasn't until I received the replacement rollers and requested a refund for the fourth time that they sent it.

They wouldn't acknowledge my suggestion that perhaps the helical cutters in the rollers are too deep. They claimed on the lowest setting with the helical rollers the mill should produce flour, but when I responded with a picture of the crush I was getting on the lowest setting they wouldn't acknowledge that either. Just completely ignored it.

One flaw I've noticed on both sets of rollers is that the flats ground into the shaft are not ground to an equal depth. This doesn't affect operation if using a Lovejoy coupler like I am on my mill table, but in a drill chuck it causes the drill to wobble a little bit as the unequal flats make the shaft off center in the chuck.

I'm glad I now have a mill that works, and I do think their mill with knurled rollers is a good product. The path to getting here has been pretty frustrating however, and if I could go back I might pick a different brand. If you assume about 5 hours of time per batch, I spent 40 hours trying to make a mill that was poorly designed work, and that's ignoring the ingredient cost of those 8 batches that didn't come out quite as they should due to low conversion efficiency. The beer still tasted good though, so perhaps I shouldn't complain about that too much

I did get my mill table finished, and am very happy with how that turned out. On a positive note, the service from All American Ale Works was absolutely fantastic when I had a few questions about their PowerGrinder motor I am using on the table.

I dropped the mill gap to 0.025" and should have a chance to brew another batch in a few days.

 

[Epos7]

Two roller monster mill set at .035 , my efficiency routinely approaches 80%

Your conversion efficiency, pre-boil efficiency, or brewhouse efficiency?

 

[doug293cz]

...

I did get my mill table finished, and am very happy with how that turned out. On a positive note, the service from All American Ale Works was absolutely fantastic when I had a few questions about their PowerGrinder motor I am using on the table.

I dropped the mill gap to 0.025" and should have a chance to brew another batch in a few days.

That's an awfully nice looking piece of furniture for mill table.

Brew on

 

[njpatg]

Your conversion efficiency, pre-boil efficiency, or brewhouse efficiency?

Brewhouse

 

[Epos7]

The weather warmed up enough here that I was able to get two batches in over the last two days. This time I made sure to stir the mash well prior to taking any samples.

Sticking with my Zombie Dust clone, and a target of 5.25 gallons into the fermenter for both batches.

10.24 lb Great Western Organic 2-Row
1.05 lb American Munich (10L)
0.42 lb CaraFoam
0.42 lb Crystal 60
0.42 lb Melanoidin

Total grain bill: 12.55 lb
Starting water volume: 8.4 gallons
Target OG: 1.065
Mash temp: 152F

Batch #1: mill gap set to 0.025"
I refired the burner at 15, 30, and 45 minutes

Mash:
15 min: 151F, 8.3 brix refractometer, pH 5.24
30 min: 151F, 10.0 brix refractometer, 10.3 brix hydrometer
45 min: 151.4F, 10.9 brix refractometer, pH 5.27
60 min: 151.5F, 11.5 brix refractometer
post-squeeze: 11.5 brix refractometer

Conversion efficiency per Braukaiser formula: 90.7%

Volume after boil and chilling wort: 6 gallons
I was barely able to collect my 5.25 gallons, with about .75 gallons left in the kettle which was composed mostly of hop leaf, plus maybe a pint of wort.

After chilling wort: 14.2 brix refractometer, 14.0 brix hydrometer


Batch #2: mill gap set to 0.022"
I refired the burner at 15 and 45 minutes (must not have stirred well enough while reheating at 15 minutes, as it was still above target temp at 30 minutes)

Mash:
15 min: 150.4F 11.3 brix refractometer, pH 5.31
30 min: 153.0F, 10.6 brix refractometer, 11.0 hydrometer - not sure why I went backwards here
45 min: 150.6F, 11.3 brix refractometer
60 min: 11.9 brix refractometer

Conversion efficiency per Braukaiser: 94.3%

Volume after boil and chilling wort: 5.75 gallons (more vigorous boil for this batch)
I used pellet hops for this batch rather than whole leaf, and was easily able to collect my target volume with some left over in the kettle, probably because with pellet hops most of them get sucked into the fermenter.

After chilling wort: 15.3 brix refractometer, 15.3 brix hydrometer


Some observations:

- I try to take all measurements with the wort temperature within 1 degree of 20C. A hydrometer tube sample takes some time to cool, and I then pull the refractometer sample from the top of the hydrometer tube. I almost always get a lower reading on my refractometer doing this, likely because while the tube is sitting to cool, more sugary dense wort collects near the bottom, so the refractomer sample I pull from the top reads lower. When I take a hydrometer sample after boiling and chilling the wort with my immersion chiller, I don't have to wait for the sample to cool, so there is less chance for stratification within the hydrometer tube. I find I get very similar readings between my refractometer and hydrometer on these measurements. In the future if I pour the hydrometer tube into a second vessel prior to pulling a refractometer sample, I may see more consistent results.

- There appears to be some disagreement on brix to SG conversion. BYO cites this formula as the most accurate. The same formula is referenced here:

SG = 1.000019 + [0.003865613(brix) + 0.00001296425(brix) + 0.00000005701128(brix)]

Taking the OG from my second batch, this formula says 15.3 brix = 1.059 SG. I believe this formula is accounting for a wort correction factor of 1.04.

On a different page, BYO cites a different formula:

{Plato/(258.6-([Plato/258.2]*227.1)}+1 = Specific gravity

This formula says 15.3 brix = 1.062 SG

This calculator uses an iterative technique to convert between the two:

Its calculator says 15.3 brix = 1.062 SG

Most conversions seem to put 15.3 brix at 1.062 SG, so I'm going with that

edit - lots of good information on the various ways to convert between brix and sg here.

- I wonder how much volume loss occurs during mash. There is a decent amount of evaporation happening, and when stirring the wort and taking measurements, the lid is off allowing some to escape. If the amount lost is significant, that would mean my conversion efficiency measurements are on the generous side.

- When boiling the second batch, I noticed that by the end of 60 minutes my boil was not nearly as vigorous as at the start. I would think that as the volume decreases, it would be easier to maintain a vigorous boil, as I had my propane burner turned on full blast for the full 60 minutes. I still have about a quarter of a tank left, but it could be lower pressure out of the tank as it runs lower. I'm not sure how to solve this without the inconvenience of not using the second half of a propane tank for brewing. Another explanation is that as the density of the wort increases, so does its boiling point.

- Brewer's Friend appears to have corrected the conversion efficiency calculation in their Brew Session tool. Their brewhouse efficiency calculator still reports a different result. For batch #1 I calculated a conversion efficiency of 90.7% using Braukaiser's formula. Brewer's Friend's Brew Session tool reports 91% conversion efficiency. Their brewhouse efficiency calculator reports 83% with the same inputs.

 

[1MadScientist]

You say you have a hydro measuring degrees Brix (°Bx). What's wrong with using this PDF table?

http://braukaiser.com/download/Kaiser_Brix_Plato_SG_table.pdf

 

[pricelessbrewing]

- Brewer's Friend appears to have corrected the conversion efficiency calculation in their Brew Session tool. Their brewhouse efficiency calculator still reports a different result. For batch #1 I calculated a conversion efficiency of 90.7% using Braukaiser's formula. Brewer's Friend's Brew Session tool reports 91% conversion efficiency. Their brewhouse efficiency calculator reports 83% with the same inputs.

I have several issues with brewers friends math, this is definitely the biggest one though. I see it all the time as it's usually one of the first google results for brewhouse efficiency, a lot of brewers use it and get incorrect results.

 

[IslandLizard]

[...] I did get my mill table finished, and am very happy with how that turned out. On a positive note, the service from All American Ale Works was absolutely fantastic when I had a few questions about their PowerGrinder motor I am using on the table.

I dropped the mill gap to 0.025" and should have a chance to brew another batch in a few days.

That table, mill, machined bottom plate, motor, everything belongs in your parlor, not the brewhouse!

The 0.025" gap on 2" rollers should give you the best BIAB crush there is. Even wheat and rye will be crushed to perfection!

 

[Epos7]

You say you have a hydro measuring degrees Brix (°Bx). What's wrong with using this PDF table?

http://braukaiser.com/download/Kaiser_Brix_Plato_SG_table.pdf

The brix column in that table is assuming you are using a refractometer with a wort correction factor of 1.04, which I don't believe mine has. Further, I think Braukaiser has applied the correction factor in reverse.

Brewer's Friend states that you should divide your refractometer reading by the WCF rather than multiply, so a reading of 15.3 brix with my refractometer would equate to 14.7 brix on the hydrometer. If that's the case, then the table is backwards, as it converts a refractometer reading of 15.3 brix to 15.9 plato. If Braukaiser has it right, Brewer's Friend has it backwards. Based on dmtaylor's discussion of WCF previously in this thread, and his references to Sean Terrill's work, I think Brewer's Friend may have the right of it, which would mean Braukaiser's table is backwards.

The plato to SG conversion in the Braukaiser table seems accurate. At least it's in agreement with the majority of formulas I found.

 

[Epos7]

That table, mill, machined bottom plate, motor, everything belongs in your parlor, not the brewhouse!

The 0.025" gap on 2" rollers should give you the best BIAB crush there is. Even wheat and rye will be crushed to perfection!

Thank you! Gotta say it beats the hell out of trying to balance the mill on top of a bucket with a drill attached

 

[dmtaylor]

@Epos7,

Brix = Plato out to like 6 or 7 significant digits. The conversion factor of 1.04 quoted by Kai is either A) wrong or B) misunderstood. In either case, ignore it because 12.0000 Brix = 12.0000 Plato (for example).

As I understand it, the correction factor of 1.04 that Sean Terrill uses is based on an average correction factor from numerous different brewers, but is specific to each individual refractometer. My own refract. seems to be the opposite with a factor less than 1.000, maybe 0.94 or thereabouts. More experiments are needed. If you want to know the factor for your own refractometer, you'll need to measure Brix simultaneous with a calibrated hydrometer and compare readings over numerous batches to come up with your own average, which may be 1.04 or may be something completely different.

As far as I know, Brewer's Friend's calculator is doing things right from what I can tell, assuming you know the WCF to put in to give you accurate results.

 

[doug293cz]

@Epos7,

Brix = Plato out to like 6 or 7 significant digits. The conversion factor of 1.04 quoted by Kai is either A) wrong or B) misunderstood. In either case, ignore it because 12.0000 Brix = 12.0000 Plato (for example).

As I understand it, the correction factor of 1.04 that Sean Terrill uses is based on an average correction factor from numerous different brewers, but is specific to each individual refractometer. My own refract. seems to be the opposite with a factor less than 1.000, maybe 0.94 or thereabouts. More experiments are needed. If you want to know the factor for your own refractometer, you'll need to measure Brix simultaneous with a calibrated hydrometer and compare readings over numerous batches to come up with your own average, which may be 1.04 or may be something completely different.

As far as I know, Brewer's Friend's calculator is doing things right from what I can tell, assuming you know the WCF to put in to give you accurate results.

My understanding is that Brix = Plato specifically for sucrose solutions. Wort is not a sucrose solution, so has a slightly different index of refraction. So, you need a wort correction factor to adjust for that index of refraction difference, in order to get more accurate SG measurements.

Brew on

 

[dmtaylor]

My understanding is that Brix = Plato specifically for sucrose solutions. Wort is not a sucrose solution, so has a slightly different index of refraction. So, you need a wort correction factor to adjust for that index of refraction difference, in order to get more accurate SG measurements.

Brew on

Hmm.... you may be right! I wasn't thinking about it very hard. You may be right. Thanks!

 

[pricelessbrewing]

The correction factor is necessary because refracts are typically designed with the refractive index of a sucrose solution. Since wort is not a sucrose solution, it won't be entirely accurate. Wort is composed of a variety of different sugars, each of which has a different index and the overall index will vary with grain bill, OG, SRM, and mash temp.

With that said, 1.04 matches most refractometers and the typical 8-15srm @ 1.05-1.065 within a certain amount of uncertainty. I don't really worry about it for the most part, as I'm okay with +- 0.001 to +- 0.002 sg.

edit: Doug beat me to it. Serves me right for typing up a response, then playing a game before hitting send reply.

 

[Epos7]

My understanding is that Brix = Plato specifically for sucrose solutions. Wort is not a sucrose solution, so has a slightly different index of refraction. So, you need a wort correction factor to adjust for that index of refraction difference, in order to get more accurate SG measurements.

Brew on

I think this is correct! Brix does equal Plato for all intents and purposes, but when taking wort measurement with a refractometer, the idea as I understand it is that you need to adjust for the different index of refraction to get the true measurement, which could be in either Brix or Plato.

I think the way Braukaiser's table is set up is the Brix column is intended to be the measured value with a refractometer. The Plato column is then the adjusted "true" value, but could also be thought of as the adjusted "true" Brix value. This adjusted Brix/Plato value is then converted to SG in the third column. My issue with the table is that I believe the standard 1.04 wort correction factor is applied backwards, ie you should see a lower value in the Plato column, not a higher value. A more accurate WCF for the way the table is designed would be 0.96.

I have taken many measurements with my refractometer (Milwaukee MA871) and a hydrometer, and I think it's WCF is about 1.

 

[1MadScientist]

Yeah, your refrac is near 1 like mine. I use the Plato to SG part of Kia's table for my refrac and short range Brix hydros

This is a nice online calculator with the formulas they use and a table; http://www.straighttothepint.com/specific-gravity-brix-plato-conversion-calculators/