Running black marks from rear windows

[Razer]

Okay so everytime i wash my car it comes out looking great, as it should! But about a day or two later, dirty water marks appear! I dont believe they are "stained" on so to speak, just rain water catching dirt trapped between glass.. Any way around this? Really irritating and ive even snowfoamed that area a few times to loosen anything trapped but just keeps happening!

 

[RS133ETO]

Do you have a picture at all? I'm not sure where you mean by "trapped between glass", but water marks is usually from washing your car. Try drying your car with a drying towel after a wash to elimate any water on there. If you mean that you've got dirt between the glass and the car, then try spraying some APC into the ingress and agitate with a long bristle brush, then hose out any remaining dirt that may be trapped.

 

[maggi200]

It's normal if you've got dirt in there. You will need to agitate the dirt properly to remove it