Black residue when cleaning SS

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guypettigrew
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Black residue when cleaning SS

Post by guypettigrew » Wed Aug 29, 2018 12:43 pm

There's always a very thin white layer on the inside of my SS fermenter at the end of fermentation. I'm guessing this is calcium.

After cleaning all the yeast etc from the FV the white stuff can be removed easily enough with a green nylon pad. Shouldn't damage the SS. But when I dry it off with some paper towel there's always a grey/black residue left on the paper. After this I spray the FV with normal strength Starsan.

Anyone know what this residue is, and should I be concerned?

Thanks.

Guy

Robwalkeragain
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Re: Black residue when cleaning SS

Post by Robwalkeragain » Wed Aug 29, 2018 1:00 pm

Probably beerstone/proteins bud. Even caustic washing won't shift it - Cleaning by hand will always leave marks - I wouldn't want to use a scratch pad near an expensive SS fermenter either. Try a soak in nitric acid/beerstone remover, empty and give it a good spray down and drain.

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LeeH
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Re: Black residue when cleaning SS

Post by LeeH » Wed Aug 29, 2018 1:13 pm

Rob, you have me thinking now.

Would beer line cleaner passivate at all?


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Robwalkeragain
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Re: Black residue when cleaning SS

Post by Robwalkeragain » Wed Aug 29, 2018 1:42 pm

Depends on the formulation but pipeline is caustic based so I doubt it. As a general rule caustic based detergents will remove organic compounds, acid non organic - you're probably dealing with minerals here, so acid wash is the way to go! Just don't let it touch copper, haha.

guypettigrew
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Re: Black residue when cleaning SS

Post by guypettigrew » Wed Aug 29, 2018 2:35 pm

Robwalkeragain wrote:
Wed Aug 29, 2018 1:00 pm
Probably beerstone/proteins bud. Even caustic washing won't shift it - Cleaning by hand will always leave marks - I wouldn't want to use a scratch pad near an expensive SS fermenter either. Try a soak in nitric acid/beerstone remover, empty and give it a good spray down and drain.
Thanks, Rwa. Malt Miller sell a beer stone remover. Looks like one full container dilutes down to about 25 litres.

Should I make the whole lot up and let it sit for the stated 10 minutes before draining, or can I just make up (say) 500ml and wipe it over the surface of the FV?

And how frequently is it likely to need doing?

Guy

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Re: Black residue when cleaning SS

Post by jaroporter » Wed Aug 29, 2018 4:32 pm

we talking like a black smudge/smut on the paper? possibly scouring the pot is damaging the stainless and causing the alloy metals (nickel) to oxidise.
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guypettigrew
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Re: Black residue when cleaning SS

Post by guypettigrew » Wed Aug 29, 2018 5:31 pm

Yes, a black smudge. I wouldn't have thought a green nylon thingy would damage the fermenter, but what do I know!

Guy

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Re: Black residue when cleaning SS

Post by a-slayer » Wed Aug 29, 2018 7:34 pm

I use a nylon scrub to clean the stubborn residue in my SS fermenter with no problems, I clean it, rinse, tip out the water then spray with starsan and let dry.

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LeeH
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Re: Black residue when cleaning SS

Post by LeeH » Wed Aug 29, 2018 10:09 pm

guypettigrew wrote:
Robwalkeragain wrote:
Wed Aug 29, 2018 1:00 pm
Probably beerstone/proteins bud. Even caustic washing won't shift it - Cleaning by hand will always leave marks - I wouldn't want to use a scratch pad near an expensive SS fermenter either. Try a soak in nitric acid/beerstone remover, empty and give it a good spray down and drain.
Thanks, Rwa. Malt Miller sell a beer stone remover. Looks like one full container dilutes down to about 25 litres.

Should I make the whole lot up and let it sit for the stated 10 minutes before draining, or can I just make up (say) 500ml and wipe it over the surface of the FV?

And how frequently is it likely to need doing?

Guy

BS remover..... that’s handy for all sorts!


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Re: Black residue when cleaning SS

Post by Robwalkeragain » Thu Aug 30, 2018 8:44 am

guypettigrew wrote:
Wed Aug 29, 2018 2:35 pm
Robwalkeragain wrote:
Wed Aug 29, 2018 1:00 pm
Probably beerstone/proteins bud. Even caustic washing won't shift it - Cleaning by hand will always leave marks - I wouldn't want to use a scratch pad near an expensive SS fermenter either. Try a soak in nitric acid/beerstone remover, empty and give it a good spray down and drain.
Thanks, Rwa. Malt Miller sell a beer stone remover. Looks like one full container dilutes down to about 25 litres.

Should I make the whole lot up and let it sit for the stated 10 minutes before draining, or can I just make up (say) 500ml and wipe it over the surface of the FV?

And how frequently is it likely to need doing?

Guy
Yeah that looks right. Can't find any info on it to confirm its acid based but I'd say it'll do the job seeing as it's sold specifically for purpose.

You can indeed recoat it, a couple of coatings over a half hour period diluted is usually enough to remove beerstone. Rinse off then use your usual detergent and watch the crap fall away. Don't mix it with anything chlorine based or you might die horribly - acid and chlorine creates poisonous gas.

I brew twice a week and do mine every 2 or 3 weeks, should be every time really as beerstone can penetrate the lining of your fermenter, but avoiding buildup should be fairly easy if you clean thoroughly each time.

Definitely don't use those nylon pads everyone is posting on an expensive SS fermenter, scratches will remove the passivation and give bacteria a nice little hidey hole to live in. You'd be better off with a plain cloth and a bit of elbow grease if chemical cleaning isn't doing enough for you.

guypettigrew
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Re: Black residue when cleaning SS

Post by guypettigrew » Thu Aug 30, 2018 11:55 am

Thanks again. I'll get some BS remover and give it a go.

Guy

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Re: Black residue when cleaning SS

Post by HTH1975 » Thu Aug 30, 2018 3:09 pm

Just a lemon/lime boil will sort you out if you don’t have citric acid concentrate/powder.

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Re: Black residue when cleaning SS

Post by Carnot » Thu Aug 30, 2018 6:17 pm

I suspect that the method that you are using to clean is probably removing the the protective oxide layer. I am not huge fan of Starsan mainly because all it is is a mixture of phosphoric acid and DDBSA. It is not the best biocide and is more a biostat. The phopshoric acid WILL not passivate the stainless steel. For passivation the standard is nitric acid or chromic acid which are not very pleasant. However citric acid is a recommended option. Follow this link. A 4-10 % solution for a relatively short time is all that is required.

https://www.bssa.org.uk/topics.php?article=68

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