This video was taken and edited by my daughter Eleanor. I was doing an aluminium pour of some parts for the Armstrong RML cannon, explaining the process to her. I was hardly aware that she was videoing, so the interaction is conversational.
Although the pour was not a success because none of the parts were good enough to use, it does show the process as seen by someone who previously knew nothing about it.
There is also a 20 minute video of the whole process which I will add to this post when it is available.
Reader Rob has suggested that the positions of the defects suggests that air entrapment is the cause of the voids and that the fix is to position some vents at the positions at risk. I will try that with my next pour. Thanks Rob.
Here is the 22 minute video. Just as recorded. Not planned or edited.