Oxidation?

Today was somewhat frustrating when we tried to frost our carrot cakes that we baked last Friday.  Our whole group had some problems with our cream cheese icing.  Danika and Nicole got their icing made, but it for some reason was too soft and so it "melted" off the cakes when they tried to frost them.  They ended up adding more cream cheese (or perhaps more buttercream) to thicken it up, and it ended up finally working for them.  Daniel and I had the problem of our icing turning grey!  We thought we had it all mixed up perfect and turned it out into a bowl so we could frost with it, but as we got to the bottom we got about a 1/4-1/2 cup of really grey icing.  Daniel (daringly) tried some of it and said it tasted like licking a pencil, ewww!!!  I took off the grey part thinking what wasn't grey was still good, but as I was wrapping it up so Daniel and I could have some dinner, Chef came by and saw it and said "Why is your icing grey?".  It hadn't seemed grey anymore to me, but I guess it was.  Chef said he thought it was probably from oxidation and that while we washed the paddle and bowl well, we didn't dry it well enough.  So we tried making it again and took plenty of time to wash and dry the equipment extra well.  We hadn't even gotten halfway into the recipe and we started getting the grey stripes in the icing again!  We showed it to Chef again and he asked us about cleaning the equipment - which we had - and then as I was composting that batch, he saw the bottom of the bowl showed marks that it had been scraped.  So the problem was that the paddle was scraping the bottom of the bowl, which is probably why the taste that Daniel tried tasted metallic - yuck!

But even after two bowls of bad icing, Daniel and I did manage to get our angel food cake checked off, a batch of lemon curd made, and our roll cakes made as well.  Tomorrow we will try again with the cream cheese icing and attempt to finish our carrot cakes.