Stainless corny with PBW foam residue

[blizz81]

I've used PBW to clean my serving kegs and my 10gal corny fermenter many many times before, sometimes leaving the PBW solution in for a week with no issues.

Recently, I filled up my 10gal corny keg with PBW solution. One thing I guess that may not have been normal - I shook it up twice immediately after filling it past the high point of krausen gunk on the side of the keg. I let it sit overnight and when I opened it up the following day, there was about a 2" ring around the top of the liquid surface on the walls of the keg that was grainy in texture. I filled the keg with more hot water to above this ring and let it sit one more night.

That didn't really do much. Scrubbing kind of eventually helps but it's a lot of elbow grease and abrasion. Tried barkeepers friend, and a vinegar solution, neither really seems to help much. Being that it was above the liquid surface, it seems it was due to contact with foam from shaking it up. Any ideas on anything else to help get it off?

 

[Bobby_M]

Hot PBW solution is very effective at cleaning scummy stuff, but you can't let it cool all the way down to room temp. It has to be rinsed with hot water without waiting several hours. You can fix it by filling the keg with hot water and adding 2 ounces of starsan concentrate. Soak for one hour, hot rinse.

 

[blizz81]

Thanks Bobby, I'll get some starsan and give it a shot (I'm still an iodophor guy for sanitization, mostly due to inertia/works for me). Between serving kegs and this fermenter I haven't had any observable issues in probably 50+ instances of leaving it sit from tap water-hot (115-120F) overnight or sometimes up to a couple days followed by a similar hot fill and soak overnight as a rinse. Figured it was something to do with the agitation in this case where you can get the PBW particles in the foam and not really in suspension in the water.

 

[blizz81]

The starsan worked well, I assume the overmix was 2oz for 5gal and used about 2.5oz for ~7.5gal. Thanks for the assist!

 

[VikeMan]

Hot PBW solution is very effective at cleaning scummy stuff, but you can't let it cool all the way down to room temp. It has to be rinsed with hot water without waiting several hours.

I often (like hundreds of times) let equipment soak in PBW solution overnight. It might take a little more rinsing, but I haven't had any problems with anything getting stuck and needing any special intervention (like acid, or whatever). And nothing like the issue OP described.

As it happens, I watched a crowdcast about passivation this morning with Emily Lovato from 5 Star, which reminded me of this thread. During Q&A, there was this off-topic question:

------------------------------
Q: How long does PBW last once mixed? Is it like Starsan where you have to say several hours but maybe longer?

A: So, PBW is most effective in the first eight hours. Is it still effective after that? Absolutely. But it's gonna give the most punch in the first eight hours, because after that the oxygen really escapes the solution, and it's just not gonna have that punch that it does in the first eight hours. Can you soak your vessels overnight and will it still be effective? Absolutely.
--------------------------------

I can't really explain what happened in OP's case (specific water chemistry perhaps?). But I know there are lots of people who PBW soak overnight, and have to assume that OP's experience was not typical. If it was, we'd be seeing more of it in the forums.

 

[Bobby_M]

I often (like hundreds of times) let equipment soak in PBW solution overnight. It might take a little more rinsing, but I haven't had any problems with anything getting stuck and needing any special intervention (like acid, or whatever). And nothing like the issue OP described.

As it happens, I watched a crowdcast about passivation this morning with Emily Lovato from 5 Star, which reminded me of this thread. During Q&A, there was this off-topic question:

------------------------------
Q: How long does PBW last once mixed? Is it like Starsan where you have to say several hours but maybe longer?

A: So, PBW is most effective in the first eight hours. Is it still effective after that? Absolutely. But it's gonna give the most punch in the first eight hours, because after that the oxygen really escapes the solution, and it's just not gonna have that punch that it does in the first eight hours. Can you soak your vessels overnight and will it still be effective? Absolutely.
--------------------------------

I can't really explain what happened in OP's case (specific water chemistry perhaps?). But I know there are lots of people who PBW soak overnight, and have to assume that OP's experience was not typical. If it was, we'd be seeing more of it in the forums.

It has to do with the source water. High carbonate well water.

 

[day_trippr]

^yup^
And then I totally agree that a hot PBW soak requires an equally hot rinse to avoid a carbonate coating.
Failing that approach and looking for a solution, a mild citric acid rinse will remove the ghostly film...

Cheers!

 

[BongoYodeler]

I recently noticed something similar as the OP. I did a hot PBW soak that turned into a week-long soak after I had to go out of town for a few days. Upon return I emptied the keg and followed up with two hot water rinses. After the keg dried I ran my hand inside and noticed grit was attached to the inside keg wall. A couple more hot water rinses did not resolve it. I remembered reading Bobby's tip - hot water and Starsan mixture, tried it, and that took care of it. My (city) tap water appears to have low carbonate level, (<1.0 ppm), but the TDS is/was high at 467 ppm. I actually installed a water softener a few days ago, not for brewing as I use Culligan RO water, but because I didn't like what my water was doing to the copper pipes and fixtures, as well as our skin.

 

[day_trippr]

My (city) tap water appears to have low carbonate level, (<1.0 ppm), but the TDS is/was high at 467 ppm.

Yikes! Hard to believe numbers like that don't involve epic bicarbonate levels.
But if it doesn't - what the heck is in that water then?

 

[BongoYodeler]

https://www.homebrewtalk.com/thread...ater-report-results-what-does-it-mean.671102/

 

[day_trippr]

Wow. There is indeed a lot going on in that water, a crapton of minerals to deposit on things if left to dry...

Cheers!

 

[Neldog0]

^yup^
And then I totally agree that a hot PBW soak requires an equally hot rinse to avoid a carbonate coating.
Failing that approach and looking for a solution, a mild citric acid rinse will remove the ghostly film...

Cheers!

I have found that citric acid is a great method to remove any films that collect over time. I have also used it for a substitute for a PBW cleaning.

 

[Bobby_M]

I have found that citric acid is a great method to remove any films that collect over time. I have also used it for a substitute for a PBW cleaning.

Any acid will do this work. If it's just residues from a long PBW soak, I assumed everyone had access to starsan. If you need to repassivate your stuff anyway then citric would be much more preferable.