This rainbow stain is not usually seen, but after I’ve soaped it and drained it with a squeezee, it’s clearly visible when I blow on the surface of the glass.
…Stop blowing on the surface of the glass…
What makes you think it’s a stain?
Usually the Low-E has bursted between the panes. It’s permanent
I thought it was a problem that occurred not on the inside of the glass but on the outside surface, so I expressed it that way.
Thank you for your answer.
Are you talking about the coating surface of low-e double layer glass? In the picture above, the side where I am burning my finger is side 1. The low-e coating surface of the window shown in the picture is number 3 (inside the opposite surface).
Can’t tell from pic but it looks like it’s from the glass being warped. Not your problem. And yes, stop blowing on the glass 
Thank you for your answer.
Can I ask you not to blow on the surface of the glass? I think it contains a message, but I don’t know! 
