The following has been submitted by Allan Kusk.
I saw this video that Bob Greenyer has presented on E-Cat World.
I tried the same with a piece of aluminium foil 100mm x 80mm. In less than 30 secnds there were holes in the foil and it looks like many holes are paired like those Bob talked about in another video some time ago.
The image below is of Al foil which has been in an ultrasonic cleaner for 30 seconds. It seems that the holes are connected as we have seen it before.