MHB said:
your talking out ur ass!
Metallic flavour has thee common causes
Metal - as is in contamination with product of corrosion
Bacterial - as is in contaminated with bacteria
Very old kits/extract - see above for why.
None of this can be fixed, definitely not by a Diacetyl rest nor by cold crashing. in fact it as the beer matures it tends to stand out more.
If you feel compelled to post and you have no idea what your talking about take a couple of seconds to Google the question before you do, might help the person who asked the question, you might even learn something and there is a greatly reduced chance that you will get a reputation for talking out your ass
Mark
I've just experienced a very similar thing to the OP.
I just bottled a Coopers Cascarillo
http://coopers.com.au/diy-beer/beer-recipes/ale/detail/cascarillo-amber-ale-recipe-pack/ and had a Cooper Australia Pale Ale kit sitting on the shelf. Threw that in and took it up to 16 litres (SG - 1.032). It got to 30c in the process :unsure:
Anyway, it started bubbling away a few minutes later (maybe a few more minutes).
So as per MHB's post I've ruled out the kit date. I did heat the water for the kit in a stainless steel pot but I think they are fine. So that leaves bacteria.
I sprayed the fermenter lid with no rinse and no rinsed my hose and spoon. I didn't want to start spraying sanitiser into the fermenter though so that might cause a problem.
When would I expect to start tasting this metallic taste if its going to happen?
Also, the OP mentioned over pitching but noone else has. I took about 600mls off into a PET which probably left about 1 to 1.5 litres of slurry. Mr Malty reckons about 128mls of slurry (thin slurry, high non-yeast %). But could overptiching also cause this problem?
BTW didn't mean to hijack, just that this was very similar to what I did this afternoon. Well except for the metallic taste, but time will tell...