Once mixed does PBW last like Star San?

I'm curious about the lifespan of PBW once it's been mixed. I searched the site but didn't see any post topics addressing this. I mixed up some PBW Saturday, and rotated bottles in for 10 hour soaks over the weekend. I bottled today and used the left over premixed PBW to clean out my equipment. It still seemed to work fine but I'm mildly concerned that maybe I'm missing something. Maybe I'm not suppose to be reusing this stuff over so many days.

Like I said, the fermenter and bottling bucket both cleaned up easily after a short soak in the PBW from Saturday. I was planning on soaking more bottles tonight unless you folks warn me off.

I would send them an email at [email protected]. In a recent podcast they advocated sending them lots of questions

I can't offer any scientific discussion, but I'll offer a datapoint: I had PBW around for almost two weeks before i dumped it last week. I basically used it to soak most everything i have for both brewing and dispensing beer and it seemed to still be effective when i dumped it. It may not have been as fast acting as when it was freshly mixed, but it was still effective at cleaning. Age didn't seem to affect it too much, more likely it was how much it had already been used. The last round of cleaning I used it for was some Erlenmeyer flasks that I picked up used. Since the flasks had been used for non-brewing activity, I felt better dumping the PBW at that point.

This is a great question; I hope you find an answer and report back here. I'm getting in the habit of keeping a corney keg partially filled with cleaners / sanitizers to stretch it a bit further. I know that with soft water, a low ph, and a pretty clear starsan solution that it will last but I didn't stop to think about PBW. I'm assuming that it's primarily the alkaline ph and maybe a detergent that's doing the cleaning so I'd guess that it will be just fine even after a long time but now I'm curious.


Adam

I remember reading something from the Dr. Bronner's soap company (they make castile/olive oil based soaps, I highly recommend their peppermint soap, it will make your junk tingle!) that you shouldn't dilute their liquid soaps ahead of use because it could allow for the growth of bacteria.

They say it generates “4-5% oxygen”. I take that to mean it contains sodium percarbonate. That part will go flat in a few hours.

http://www.fivestarchemicals.com/wp-content/uploads/PBWTech2.pdf

I start with PBW to use the chelates to soften the water and then after it’s dissolved I add OxiClean. You can use about a third as much PBW this way depending on how hard your water is.

I keep a PBW/Oxi solution in the sink most of the time to soak bottles as I use them. If I have some left over the next day, I’ll recharge it with a little Oxi.

When mixed in an aqueos solution the sodium percarbonate will undergo the following.

2Na2CO3.3H2O2 → 2Na2CO3 + 3H2O2

The hydrogen peroxide will then decompose by the following

2H2O2→ 2H2O+O2

Which is thermodynamicly favorable.
This is going to be dependant on temperature, pH, peroxide concentration and organic matter that gets oxidized. A good portion of the cleaning power of PBW comes from the strong oxidizing properties of hydrogen peroxide. Due to the fairly rapid decomposition the formulation will have a diminishing cleaning value with time.

Brad2287 said:

When mixed in an aqueos solution the sodium percarbonate will undergo the following.

2Na2CO3.3H2O2 → 2Na2CO3 + 3H2O2

The hydrogen peroxide will then decompose by the following

2H2O2→ 2H2O+O2

Which is thermodynamicly favorable.
This is going to be dependant on temperature, pH, peroxide concentration and organic matter that gets oxidized. A good portion of the cleaning power of PBW comes from the strong oxidizing properties of hydrogen peroxide. Due to the fairly rapid decomposition the formulation will have a diminishing cleaning value with time.

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The Fivestar MSDS say it is just Sodium metasilicate (well 30%) and does not list any other ingredients. Surely if it had sodium percarbonate it sould be listed on there as well.

Not necessarily. According to the hazardous communication standard of OSHA only hazardous substances above 1% must be listed on an MSDS. Skin sensitizers and carcinogens above .1%. Any thing that is not classified as hazardous is up to the discretion of the manufacturer.

Brad2287 said:

Not necessarily. According to the hazardous communication standard of OSHA only hazardous substances above 1% must be listed on an MSDS. Skin sensitizers and carcinogens above .1%. Any thing that is not classified as hazardous is up to the discretion of the manufacturer.

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But I would bet there would be more than 1% percarbonate in it if there was and sodium percarbonate is a hazardous substance (oxidiser and toxic).
I just noticed on the tech sheet that is warns it contains sodium carbonate -and the comment of oxygen production seems to point towards sodium percarbonate.

I think if they are not listing it they are pulling some MSDS trickery.

In order to test this I set up a permanganate titration for hydrogen peroxide. This was only qualitative as I did not have time to standardize or perform a verification/validation of the MOA. I mixed 5 grams of PBW in a volumetric flask and diluted to 100 ml. The 100 grams was added to 250 ml DIW and 10 ml concentrated sulfuric acid. This was titrated with a ~ 0.3 N potassium permanganate solution to a pink endpoint indicating the presence of hydrogen peroxide.

This does not answer the question of how long PBW will last however. It could be interesting to set up the method quantitatively and analyze at set time intervals starting at Time=0. This would give you an idea of the rate of decomposition of the hydrogen peroxide. This however does not take into account factors such as varying organic load.

PBW still does have chelating agents, surfactants, and an alkaline pH so even with out the oxidizer it will still retain decent cleaning power. I like the idea of recharging a solution with oxiclean/sodium percarbonate in order to keep the effectiveness.

Wynne-R said:

They say it generates “4-5% oxygen”. I take that to mean it contains sodium percarbonate. That part will go flat in a few hours.

http://www.fivestarchemicals.com/wp-content/uploads/PBWTech2.pdf

I start with PBW to use the chelates to soften the water and then after it’s dissolved I add OxiClean. You can use about a third as much PBW this way depending on how hard your water is.

I keep a PBW/Oxi solution in the sink most of the time to soak bottles as I use them. If I have some left over the next day, I’ll recharge it with a little Oxi.

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How much oxyclean do you add to recharge the solution?

Nice to have a chemist on here, Brad2287. It’s a breath of fresh air after so many threads with people that don’t know, vigorously repeating things that they’ve heard ‘somewhere’. It’s the Internet. Somebody says something reasonable and everybody repeats it. Then if you develop actual facts you get ignored because you’ve gone against the conventional wisdom.

I’ve never figured out the MSDS. It seems like they’ll go on about something pretty harmless and then give the exact same advice for something that is actually tricky to handle.

Label Precautions:
Do not get in eyes, on skin, or on clothing.
Avoid breathing dust.
Keep container closed.
Use with adequate ventilation.
Wash thoroughly after handling.

Anyway, re the oxygen, based on my experience with it, my guess is that the oxygen would be about half after 2 hours, and mostly flat in 8-12 hours. Hot water and swishing it around will make this happen more quickly, as would a high soil load.

alabamy, about half as much as the PBW. That's probably more than I need, but it works.

So.... The answer is "no"?

(PBW solution degrades rather quickly and storing it for an extended period of StarSan will dramatically reduce it's efficacy?)

Can the chemistry-types dumb this down to a 5th grade level for me?



Adam

biertourist said:

So.... The answer is "no"?
(PBW solution degrades rather quickly and storing it for an extended period of StarSantime will dramatically reduce it's efficacy?)
Can the chemistry-types dumb this down to a 5th grade level for me?
Adam

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5th grade translation: The ingredient which 'super-charges' the cleaning power of PBW is all gone, and the PBW liquid won't work quite as well after it is gone.

10th grade chemistry translation: The chemical that decomposes to produce oxygen gas has run out.

I re-use PBW for a week continuously all the time. It definitely works much better at the start (which is when I will use it to clean my equipment) but it's great for getting labels off bottles for a long time after. After cleaning, I just dump it into an open bucket and soak bottles in it. I only change it out when I'm making new PBW to clean my equipment again (which is never more than a week or two). Sure, the liquid gets weird colored from colors leaching out of the bottle labels, but it still works like a charm. Most of the time, the labels slide right off when I pull them out of the solution.

andrewmaixner said:

5th grade translation: The ingredient which 'super-charges' the cleaning power of PBW is all gone, and the PBW liquid won't work quite as well after it is gone.

10th grade chemistry translation: The chemical that decomposes to produce oxygen gas has run out.

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Andrew wins the "like"! Thanks Andrew! Me more smarter now. ; )

andrewmaixner said:

5th grade translation: The ingredient which 'super-charges' the cleaning power of PBW is all gone, and the PBW liquid won't work quite as well after it is gone.

10th grade chemistry translation: The chemical that decomposes to produce oxygen gas has run out.

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toddler translation -> Soap go bye-bye.

b-boy said:

toddler translation -> Soap go bye-bye.

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Except that for old PBW the soap part is what is still there It's the oxidizing capability that is gone.

Brew on

doug293cz said:

Except that for old PBW the soap part is what is still there It's the oxidizing capability that is gone.

Brew on

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Oxidizing Agent go bye bye just doesn't work.