Matt wrote:

North Carolina surgeons unwittingly used dirty tools
RALEIGH, N.C. (AP) - Sometime last year, elevator workers at two
hospitals drained hydraulic fluid into empty soap containers and capped
them without changing the labels.

When work was slow in the engineering test lab where I was working, I
used to do maintenance on the machine tools. I decided that the
vertical mill looked a little shabby, so I decided to paint it.

I found a can of grey paint and what I thought was paint thinner. But
one of the other guys in the lab had used that can to save prussian
blue layout fluid without re-labeling it.

As I poured the supposed thinner into the grey paint, I noticed how
dark it looked, but the darkness vanished as I mixed it into the paint.

Later on, after the paint dried, the vertical mill was purple...