Copper Kettle issue / Parm

[Sir Loin]

So, this is my first post, been making cheese for a while.  Today I made my first parm, and also for the first time I used an old copper kettle that I have. The kettle is BIG and OLD as you can see from the pictures below.  Yesterday I cleaned it thoroughly with a vinegar and salt solution and this morning I washed it with hot water and also disinfected it with a standard bleach solution.  There is no getting all of the patina off of this pot, and if it ever had a tin or nickel coating on it, its not there any longer.  My 8 gal. parm make went well except ... the cheese has an ever-so-slight green tint, obviously from the copper.  After some googling, I convinced myself not to worry too much about copper toxicity (or should I be?) because the curd was pulled from the kettle at a PH of 6.3 which should not be acidic enough to react with the copper too much.   Unless the consensus is that this should go in the dust bin, does anyone have advise on how to get the rind to 'overcome' the green tint?  Normally, I would not do anything to a parm rind except salt and maybe oil.  But in my head, this is a cosmetic issue.  I added 9 drops of annatto into this make, so I am thinking that after long aging the inside might obtain the right hue ...  Also, this might come out of the brine looking just fine ... I am always amazed at these albino looking cheeses that somehow look yellow a few weeks later.  Thanks for any help and cheers all!

[ArnaudForestier]

Unequivocally, I would not eat this.  Green in copper is verdigris, your pot has it extensively, and that is absolutely poisonous.  I could be wrong, but I believe that's what you've got going and it's not simply copper leaching into your curds (in which case, you'd pick up some copper - still not great, especially over time, but at least it's not poisonous like verdigris).  Forgetting even this - the old adage If in Doubt, Throw it Out is a good one. 

Strongly suggest you toss this wheel and thoroughly clean the pot.  Sorry, man.

[Sir Loin]

Thanks! I can see you are correct and I think I was engaged in a bit of wishful thinking.  I just finished tearing it in half and tossing it.  But I think I learned something about PH at pressing.  After tearing it in half, I noticed that the PH at the surface and side of the cheese was significantly lower (about .15 lower) than in the middle of the cheese.   I could never figure out what to measure at pressing, the cheese or the whey.  So, I think the whey is closer and probably will let it overshoot a bit in the future.  Cheers,   

[ArnaudForestier]

I actually do both, typically.  I'll take a small sample of curds from the vat, say, 1/4 cup, and try to keep it under the same conditions as my pressing curd.  Not an ideal measure, but pretty close (I have some leeway, given all I do are alpines).  I also measure whey.  Whey is going to be a bit higher.  Can't recall exactly, but I believe Pav might have said, by +.02 or .03.  Don't quote me. 

Good luck!

[Alpkäserei]

Get yourself a 3m scotch pad -one of those green scrubby things for cleaning pots and pans-
Use that to clean your copper.

Put vinegar in salt, like you said, but scrub over a gentle heat. You need to add heat to the mix to get the ingredients to react with each other, using copper as a catalyst. Vinegar will not react with salt by itself, but if you add energy you get a reaction to form small amounts of hydrochloric acid. This is what cleans copper.

So use this, scrub with the green pad, then rinse out IMMEDIATELY and clean with cold water several times. If you do not, the copper will immediately tarnish and form new verdigris. Vinegar and salt is to be used only to strip a heavily tarnished or verdigris surface. Otherwise just scrub with a scotch pad and water.

I have never encountered a situation where you could not get the copper clean, and I have faced some nasty stuff.

It is extremely important to have no green at all when using copper. This is poison, it will kill you.
Copper is a wonderful substance, but with it comes a great deal more responsibility than you have when using steel.

Don't ever let milk near green copper. It will react and form copper sulfates. Deadly poison.

[qdog1955]

May I suggest---after using anything acidic on copper, rinse with cold water mixed with baking soda( to neutralize acid) then rinse with cold water). To remove verdigris, You can also use a buffing wheel with non waxed compound( normally used in buffing steel for guns, in prep for bluing) You can use waxed compound such as brown Tripoli---but then have to remove the wax film left behind.
  You should be aware that verdigris is the natural patina that copper forms to protect it self, the same way aluminum forms a patina as protection from further corrosion. The problem with copper is different types of verdigris(chemically) are formed by exposure to different elements--water-- salts--acids---some more harmful than others, to you and the copper.

[Sir Loin]

Thanks for the tips.  I was ready to put the thing back in the attic but now I will try again.  The copper really was a pleasure to work with.  It warmed evenly and seemed to keep temperature exactly where I wanted.  So, vinegar, salt, and elbow grease, here I come.