Author Topic: "Varnish" in Fermenter  (Read 1033 times)

Offline mabrungard

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"Varnish" in Fermenter
« on: January 25, 2015, 06:52:56 PM »
I just noticed an interesting buildup in my stainless conical fermenter.

I thought I had been keeping my fermenter perfectly clean for over a decade, but I noticed prior to my last brew that it had a very light tint on the interior surface. Since I spent days polishing the interior of the fermenter when I bought it, I have always avoided hard scrubbing with scrubby pads. But I have always been thorough in scrubbing the surface with either my hand, thumbnail, or sponge to remove any sort of trub, yeast, or other deposits. It always looked clean and shiny.

So with some 60 or 70 batches fermented in that vessel, I happened to notice that there was a tint to the stainless surface. I used my thumbnail and was able to scrape it off...grudgingly. It was some sort of a transparent, tan coating that I guess could be termed "varnish".

I still didn't want to use a scrubby since that is known to create micro scratches in metal surfaces. So I tried a warm PBW soak. That helped a bit, but I'm pretty sure that it's ~110F temperature was not enough to really activate the solution. I then hooked up my RIMS and circulated the solution at 160F and it further loosened the layer. I could get more off with my nails. Ultimately, I pulled out a white scrubby and lightly scrubbed the surfaces to get all the varnish off.

It's clean now, but I have to wonder if critters may have been lurking in that microscopic varnish layer that may not have been knocked out with sanitizer? Fortunately, my prior beers have been good, but that question has to remain.

While this event hasn't diminished my avoidance of harsh scrubbing with a scrubby since its obvious to me that the micro scratches will eventually become filled with that varnish, I wonder if anyone else has experienced this?

The good news for me now is that I know that I need to perform a substantial PBW cleaning in order to remove something I can't even see, on a frequency a little greater than once in 60+ brews.   :)
Martin B
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Offline Stevie

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Re: "Varnish" in Fermenter
« Reply #1 on: January 25, 2015, 07:11:05 PM »
Is it beer stone? We were just talking about this at a club event yesterday. One member recommend mixing 50/50 vinegar and water to make cheap and safe acid wash.

Offline brewinhard

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Re: "Varnish" in Fermenter
« Reply #2 on: January 25, 2015, 07:56:42 PM »
Good on you for even catching it.  I can't tell you how many guys in my LHB club would not even think twice about that.  My kettle needs a good PBW soak to get rid of some of the built up beer stone in there, but thank god it is not a fermenter.  At least you are now aware of the "staining" and can keep an eye on it over time. 

Offline mabrungard

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Re: "Varnish" in Fermenter
« Reply #3 on: January 25, 2015, 10:03:32 PM »
Definitely not beerstone.
Martin B
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Offline Thirsty_Monk

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Re: "Varnish" in Fermenter
« Reply #4 on: January 26, 2015, 03:37:03 AM »
Alternative acid and alcaline cleaner can also help.
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Online blatz

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Re: "Varnish" in Fermenter
« Reply #5 on: January 26, 2015, 02:51:35 PM »
yes, i have noticed the same martin.
and a hot (140df+) recirculated soak of PBW for a few hours tends to help a lot. i generally try to use a dishrag to scrub the interior periodically during the soak to help loosen up the layers. 

as TM mentioned, alternating with an acid soak helps tremendously.  I find that Five Star Acid #5 does the trick.  its weird, but its very satisfying to see that perfect metal shine after the acid has done its thing. 

I put it on my calendar to try and run this process on my boil kettle, HERMs coil, and conicals about every 6-9 months based on when I have a lull in brewing.  I just did the BK and coil last weekend and will probably run it in my conicals this coming weekend as I don't expect to brew for a few more weeks.
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Offline majorvices

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Re: "Varnish" in Fermenter
« Reply #6 on: January 27, 2015, 12:06:49 PM »
Definitely not beerstone.

Really? Cause it sounds just like beer stone! On my stainless I always do a caustic wash followed by an acid rinse and then passivate every 4 months or so. Pretty important to use acid to remove non-organic deposits on stainless.

Offline narcout

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Re: "Varnish" in Fermenter
« Reply #7 on: January 27, 2015, 05:19:07 PM »
If the LHBS does not carry it, where can one buy Acid Wash #5?  I see a couple of on-line retailers, but they are selling it in large quantities, and the shipping is crazy expensive. 

Is there something more readily available that works well for removing beerstone (white vinegar, concentrated Star San, etc.)?

I've definitely got something building up in my fermentor that sounds very similar to what Martin is describing.  It hasn't caused my any issues yet, but I would like to get rid of it. 
It's too close to home
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Re: "Varnish" in Fermenter
« Reply #8 on: January 28, 2015, 11:39:01 AM »
The last time I used the Acid Wash from 5-star I actually bought it with a bulk grain order through Country Malts (went in with several other homebrewers.) I get my chemicals delivered now. I doubt that vinegar would work.

The acid wash I got from NCM lasted me about 2 years for 1 gallon. In fact i never used it all and suspected it lost its efficacy because it changed from pink to clear. Wonder if MoreBeer would carry a smaller volume of it?

Offline beersk

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Re: "Varnish" in Fermenter
« Reply #9 on: January 28, 2015, 01:51:18 PM »
Why couldn't one use barkeepers friend for this?
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Re: "Varnish" in Fermenter
« Reply #10 on: January 28, 2015, 02:39:42 PM »
Why couldn't one use barkeepers friend for this?

I've always been leery about using it on the inside of my SS conicals - maybe unfounded, but I just want to avoid scratching.
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Offline beersk

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Re: "Varnish" in Fermenter
« Reply #11 on: January 28, 2015, 04:13:55 PM »
I didn't think scratching stainless was as easy as you guys are making it sound.
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Jesse