Looks like milk running of frames

[super mck]

Why are some frames running  like milk down them.its doing my nut in ?

 

[Pjj]

Why are some frames running  like milk down them.its doing my nut in ?

Its the dead surface of plastic coming off if it’s plastic , if it’s painted wood it’s the dead top surface of the paint give it a good scrub it should be less to non existent on the next clean 

 

[Dave B]

You just need to scrub all the oxidisation off and then it is fine if cleaned regularly 

The sunlight causes most of it 

 

[Part Timer]

Why are some frames running  like milk down them.its doing my nut in ?

I'll assume this is happening on first cleans, if it is happening regularly you need to clean until the milk clears up. As @Pjj and @Dave Bsays it's the surface that has broken down 

 

[steve garwood]

If it’s really old aluminium windows, it will be the powder coating has failed.

Even after loads of washing these can be an absolute pain with WFP