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Home Brew Forums > Home Brewing Beer > Equipment/Sanitation > Star San cloudiness lab report
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Old 02-14-2009, 01:48 AM   #1
Pejepscot
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Default Star San cloudiness lab report

Hi Folks,

I performed this quick study to reassure myself and others who might be in the same situation using Star San.

I found that when I mixed up Star San at the rate of 0.5 oz per 2.5 gallons in my tap water it became cloudy instantly. Normally cloudiness indicates that your Star San is no longer effective (ie, the pH has risen above 3.0) so I took some to my lab today and tested it out...



Here you can see the Star San mixed at the above rate (6.0 mL per gallon of tap water) after just one minute. (Look in the BIG beaker that the pH meter's electrode is dangling in) It is already quite cloudy, but the pH is at 2.46 using a Mettler-Toledo pH meter with two point standardization at pH4.0 and 7.0.




This is a close-up showing the cloudiness after 10 minutes - it's REALLY cloudy, but the pH is still below 3.0 at 2.45 - hooray!.




Here you can see the Star San mixed in tap water next to a batch of Star San mixed at the same rate in our lab grade deionized R/O water . This water has been deionized to the level of 18.25 megohms per centimeter - high purity water. The deionized water+ Star San is essentially perfectly clear and colorless and remained that way with a pH of about 2.25.


Here is some of the test data:

1 gallon tap water+6.0mL Star San (Tap water pH = 6.88)

Time (min) pH observation
0 2.46 cloudiness apparent immediately
3 2.43 increased cloudiness
5 2.45 very cloudy
10 2.45 "
15 2.46 "
30 2.44 "
90 2.41 "
120 2.41 "


1 gallon DI/RO water+6.0mL Star San (DI/RO water pH = 5.54)

Time (min) pH observation
0 2.28 clear and colorless
3 2.28 "
5 2.26 "
10 2.25 "
15 2.25 "
30 2.25 "
60 2.24 "


My tap water clearly has some component that is reacting with the surfactant in Star San and causing immediate cloudiness, but not affecting the pH.

Here are my tap water test results (with max allowable concentration in parenthesis)

pH 6.6 (6.5-8.5) SU
Chloride 53 (250) mg/L
total hardness 114 (*)
calcium 33 (no max listed) mg/L
copper 0.045 (1.3) mg/L
iron 0.058 (0.3) mg/L
magnesium 7.4 (no max listed) mg/L
manganese 0.043 (0.050) mg/L
uranium 4.1 (30) ug/L

(*less than 150 considered softer than ideal)

It seems to me that the calcium and magnesium must be the culprits.

CONCLUSION:

It seems that if your Star San gets cloudy very quickly when diluted in tap water, this DOES NOT INDICATE THAT THE STARSAN HAS LOST ITS SANITIZING ABILITY. I plan to make my StarSan fresh each day that I need it and I feel secure that it will stay below pH3.0 for the entire day and be an effective sanitizer.


RDWHAHB!



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Old 02-14-2009, 04:34 AM   #2
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I make 5 gallon batches and leave it in an extra primary bucket.

I make a new batch every month or two.


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Old 02-14-2009, 04:50 AM   #3
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Thanks a bunch for taking the time and effort to scientifically test your problem and post the results. This is always so much better than speculation!

If you feel so inclined to continue this test, it would be very interesting to see what the pH reading on those samples would be after they had been stored in some sort of simple plastic or glass container for a period of 4-8 weeks. I hate the thoughts of mixing up 5 gallons of this stuff so often, but I do it anyway. I bet that Star San stored in a glass jug with a lid will hold it's pH for quite a long time, depending on what it gets diluted with as it is used...

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Originally Posted by Pejepscot View Post
Hi Folks,

I performed this quick study to reassure myself and others who might be in the same situation using Star San.
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Old 02-14-2009, 05:00 AM   #4
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The other thing we know is that for 79 cents buy a gallon of distiled water and you will know that when it gets cloudy it is time to replace it.
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Old 02-14-2009, 05:12 AM   #5
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Quote:
Originally Posted by lapaglia View Post
The other thing we know is that for 79 cents buy a gallon of distiled water and you will know that when it gets cloudy it is time to replace it.
I think that there will be a little more to it than that. The cloudiness is not an indicator of acidity or alkalinity. In the case of this test, the cloudiness is being caused by a reaction with something in the water that isn't affecting the pH of the solution. Mixing additional solubles into the solution could affect the pH without showing signs of cloudiness, which might render the Star San useless with no visible indications.
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Old 02-14-2009, 11:20 AM   #6
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I think the cloudiness example is given as a rough estimate. Kind of like saying fermentation is over when the krausen drops. It doesn't always mean fermentation is complete. If you have the ability to test the pH, that is definitely the way to go.

I typically only mix a squirt bottle up at time (~500ml). You don't need to soak anything in star san, as long as the surface is wet (or foamy) it's working, and it doesn't need to stay wet that long.

If you can, I would also be really interested in see the same test performed (on the same samples) after a few weeks. As you mentioned, something in the tap water is reacting with the StarSan. It's fair to say that cloudy starsan at the time of mixing may be OK, but after a month....?

Thanks for the detailed write up, this is good stuff!
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Old 02-14-2009, 12:04 PM   #7
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Cool, thanks for this write up! +1 on leaving the samples sealed up for a month and see how the pH changes over time.
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Old 02-14-2009, 01:52 PM   #8
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Great thread. Nice touch and great demonstration. I've been meaning to do some DO 'experiments' as I have access to a YSI meter. You've inspired me to get off my a$$ and do it.
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Old 02-14-2009, 01:55 PM   #9
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Great job!!!!!
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Old 02-14-2009, 02:06 PM   #10
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Thank you for doing this. I have been wondering about this topic myself.


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