Please don’t use a copper bar. You will have no idea of how much copper you are adding. This could easily encourage oxidative darkening of the cider. See the extract from my book below. This teaches you how to add a measured dose of copper sulphate for sulphite removal. There is also much discussion of this topic in the group archives which i suggest you read.
“If your cider smells of rotten eggs, drains or is generally ‘unclean’ then it may have a sulphur taint. Unfortunately most volatile sulphur compounds in fermented beverages are odour-active at very low levels, even parts per trillion in some cases, so these can be very noticeable even when present in minute amounts. Many ciders do smell slightly sulphurous when in the course of active fermentation but this usually disappears quickly at the end of fermentation. If the smell does not disappear, excess hydrogen sulphide (H2S) or a related compound may be the cause. This can be tested by taking a small sample of the offending cider in a glass and dropping a brightened copper penny or a piece of copper wire into the sample. After ten minutes or so, its aroma should be assessed against an untreated control glass. If the offending aroma has disappeared or is reduced, it is possible to treat the bulk cider by the addition of copper (cupric) sulphate. This is a permitted practice for winemaking in the EU but only very small amounts of copper are used. (Excess copper can have adverse effects on both cider colour and flavour by encouraging unwanted oxidation as described later.)
The addition required is one part per million which is an extremely small amount to measure. The best way to do this is by ‘serial dilution’. For instance a 1 per cent solution can be made up by dissolving 5g of copper sulphate (a flat level plastic teaspoon) in 500ml of water. Then 5ml of this solution (a level plastic teaspoon) can be dispensed into 50 litres of cider to give the required level. Wait a day to see how well it has worked; one (or exceptionally two) further teaspoons may be added if required. The copper combines with the hydrogen sulphide to form cupric sulphide which is insoluble. It is also possible to buy bentonite impregnated with copper salts (such as Kupzit) which does the same job but minimizes the amount of residual copper passing into the cider.
The chemistry of sulphur in wines and cider is exceedingly complex, and if disulphide compounds have been formed after some time in storage it may be necessary to ‘reduce’ them before copper treatment by the prior use of ascorbic acid (Vitamin C). A professional winemaking textbook should be consulted for further details. It has been claimed that sulphur taints were not so much of a problem in a previous era when brass or bronze (copper alloy) fittings were common on tanks and pipework, since the transient contact with the metal acted to remove them.!”
Andrew
Thanks, I will give that a try !