CorgiBrew

Recipes 

I just got a few hundred pounds of fresh wine grapes up from Chile (booya!), and I'm thinking repurposing my SS beer keggles for the primary fermentation. Some of the plumbing in the Keggles (it's a HERMS system) is made of copper and brass (e.g., dip tubes, ball valves). Also, one of the keggles has an electric hot water heater element in it. Should I be worried about interactions between the wine must and these metals? I'm only going to use them for primary fermentation, which means the exposure will be 4 days to a week.

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I'm sorry, Dave, I can't let you brew that.

CandleWineProject

Recipes 

I don't know about wine, but copper turns cider green.

http://www.cider.org.uk/part5.htm
Discolouration of ciders (apart from the normal golden-orange colour of partly oxidised tannin) is nearly always caused by metals. Iron gives rise to blackening and copper gives greener hues, due to reactions between the metal, the tannin in the cider and the oxygen in the air. Often the colour does not develop until a bottle is opened and the air can get in - the colour then develops in minutes or hours. To confirm this, a pinch of citric acid may be added to a freshly-opened control sample. If this darkens at a significantly slower rate than the problem bottle, then iron is the probable cause. There is not much that can be done to cure the problem although re-bottling in the presence of citric acid may be considered. A technique known as 'blue fining' can be used on a commercial scale to remove the metal but only in the hands of a trained chemist. Such problems will never arise if the proper sort of processing equipment is used so that free iron and copper cannot get into the cider.

CorgiBrew

Recipes 

Well, that doesn't sound very nice. I wonder how the copper gets into the cider, e.g., what length of exposure. In any event, that's enough to convince me to replace my copper dip tube with SS.

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I'm sorry, Dave, I can't let you brew that.