Copper Pot Grey Stock

Joined Mar 4, 2017
Hello I was wondering if anyone could tell me why my copper pots are turning my bone broths grey? I have had the re-tiinned with in the past year and always start with cold water. The stock is only boiling at eh very start in order to get to a simmer. Thanks


Joined Feb 16, 2017
1. Impurities
2. Heat

Discolored stock is a sign of impurities. Stock cannot be boiled. Boiling releases both fats and impurities. And according to Thomas Keller, that high heat will emulsify the impurities into into the liquid and causes discoloration.

Start with clean bones, rinsed well in cold water, careful to remove any bits of organs and blood. Blood protein will coagulate and discolor the stock.

Start with cold water and just the bones, no vegetables or aromatics , on low heat. Start skimming as soon as impurities rise up. The scum will begin to rise before the stock is at a simmer, it's important to start the skimming at the first sign of scum, and continue until it reaches a simmer. If it's chicken stock, add ice when it's at a simmer. Ice will coagulate the fat so you can see it and remove it.

After removing the fat, add vegetables and aromatics, then agin very slowly bring it to a simmer--and keep skimming. Don't let it boil.
Joined Mar 1, 2017
I don't think its your tin lined copper.  The temperatures that your are using are more than likely not hot enough to cause an issue with the tin.  I say this on the assumption that the tin smith who relined your pots is reputable and did the work properly.  If not, then, I shudder at the thought.  :)

But, if you could provide some details about your ingredients i.e. are the bones roasted, what type of bones and the other ingredients and when they are added, you will probably get a better answer to your question. 
Joined Sep 18, 2010
Years back we always blanched all our bones for stock first. A practice that is forgotten by most but very effective when a clear stock is wanted..

You start with cold water and washed bones. Bring it to a boil fist ,then wash off the bones in cold water and rinse off all impurities visible and then start again with cold water. . Do not add your vegetables until it starts to simmer !

And make sure it never ever comes to a full boil, : only slow simmering..
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