Changing color from gold to dark

I got a Patersbeer all grain ,the golden color in the Primary went into the Secondary and in 24 hours it turned completely black.  I used a plastic bucket for  the primary formation and transfer  to the carboy.
Does anybody knows what happened ? Is the batch contaminated ?

Do you think it is oxidized?  Transferring (racking) from one vessel to another comes with the risk of oxidation. Give it a taste and see what you think.

Completely black?  I can’t think of any natural cause for that.

That wouldn’t make it completely black, though.

I think it encountered something in the transfer process that caused a chemical reaction - starches and iodophor?

That was my first thought, but it would take an awful lot of both starch and iodine to color that much liquid black.  Doesn’t seem possible.  I wonder if the description of the color could be clarified.  Does the OP really mean black, like Guinness, or just somewhat dark?  Could be a language issue.

Agreement on this.  I ran a couple searches online and one of the most common things mentioned was a large sediment drop after moving the beer to secondary, and the beer appearing darker afterward.

The beer can also look darker in a carboy where not much light is getting through due to the volume.

This really just sounds like looking at the fermenting beer and seeing the yeast in sediment in suspension and then seeing the sediment drop out. It will always look darker once the milky-white sediment drops out and the beer begins to clear. Take a sample in a small glass and analyze the color that way. RDWHAHB!

I agree with majorvices. Think of the color difference before pitching the yeast and when fermentation is in full swing. Once most of the particulate matter drops out the appearance changes dramatically. This is especially noticeable in dark beers. Keep in mind that the beer will look much lighter once you get it into a glass.

Yes, darkening in bulk versus in a pint glass versus a narrower glass is likely what occurred here, but “black”?  That is what threw me…

Yep.  There’s lots of stuff that will cause a beer to darken, but I can’t think of any that will make it turn black.

Never did get the OP back to close the loop. Wonder what happened.