I have white marks on my windows

Hello all,

I've looked around this forum but couldn't find if anyone has already asked my question before. If I've missed this in another thread, please link me to it exter:

So my question is that my bay windows have white streaks running down from the top of my windows on the outside glass. They don't come the full way down, maybe 30 to 50cm. They have been there a while, do you know what they could be?

Thank you

Everyday tortoise said:

Hello all,

I've looked around this forum but couldn't find if anyone has already asked my question before. If I've missed this in another thread, please link me to it exter:

So my question is that my bay windows have white streaks running down from the top of my windows on the outside glass. They don't come the full way down, maybe 30 to 50cm. They have been there a while, do you know what they could be?

Thank you

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Are you sure they arnt between the pains of glass .? White streaks quite often happen like this when the seals on the glassing unit break down allowing damp in between the pains 

Pjj said:

Are you sure they arnt between the pains of glass .? White streaks quite often happen like this when the seals on the glassing unit break down allowing damp in between the pains 

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Thank you for your reply. That has actually also happened. 

There are white marks between the glass as well. But there are white lines coming from the top of the exterior of the glass too.

Is it not limescale which has came from years of constant dripping from air vents at top of window?

Something I deal with quite often is white or grey marks caused by old painted stonework/tiles or untreated lead flashing just above the window. When rain water runs over it and down the glass it leaves milky stains that over time can become quite stubborn to remove. Most often they can be removed with a damp microfibre cloth.

As above I was going to suggest lead run off, you could try a bit of Cif.

Everyday tortoise said:

Hello all,

I've looked around this forum but couldn't find if anyone has already asked my question before. If I've missed this in another thread, please link me to it exter:

So my question is that my bay windows have white streaks running down from the top of my windows on the outside glass. They don't come the full way down, maybe 30 to 50cm. They have been there a while, do you know what they could be?

Thank you

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Sometimes when bay windows don’t have gutters above them then rain etc (or pure water if the window above has been cleaned) will gather on the flat roof above the bay and then run down the glass. 

Thank you all for your replies.

scottish cleaning service said:

Is it not limescale which has came from years of constant dripping from air vents at top of window?

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There aren't any vents at the tops of these windows, they're 5 panes, left of bay, right of bay and 3 in the middle with 2 opening windows.

Marko067 said:

Something I deal with quite often is white or grey marks caused by old painted stonework/tiles or untreated lead flashing just above the window. When rain water runs over it and down the glass it leaves milky stains that over time can become quite stubborn to remove. Most often they can be removed with a damp microfibre cloth.

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Martyn said:

As above I was going to suggest lead run off, you could try a bit of Cif.

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Sorry I should have said there is another flat above and the PVC panelling continues above and into another bay window too.

So it's 1 long box of windows (of flat above), PVC panels, my window, some more PVC panels

I see, try some white vinegar or limescale remover on a cloth to see if it makes a difference. ?

Could it be coming from where the PVC above is fastened to the wall above. Sometimes if you look up there will be a dark line running down from this point and this could be dripping down onto your window. If it is you'll need a PVC restore type chemical to be applied and taken off.

Even the PVC panelling itself could be at fault if it’s old, as the finish sometimes breaks down with age. You can tell if this is the case by running your fingers over the panels. If it leaves a chalky residue on your fingertips this could be the cause of your marks.

Marko067 said:

Even the PVC panelling itself could be at fault if it’s old, as the finish sometimes breaks down with age. You can tell if this is the case by running your fingers over the panels. If it leaves a chalky residue on your fingertips this could be the cause of your marks.

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I have done just that and it seems to be exactly as you say, I wiped my hand along them and my fingertips were white. 

Everyday tortoise said:

I have done just that and it seems to be exactly as you say, I wiped my hand along them and my fingertips were white. 

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I was going to suggest exactly what Mark said. I have come across that several times and now when I suspect it's oxidised frames I wet my fingertip and draw it down the frame with firm, even pressure. The dampness seems to show it up very easily.

The problem could have been caused by any one of the suggestions above though. ?

Everyday...get your /a local (pure water using) window cleaner to clean the upvc above when they clean your windows....initial clean of upvc will generate a fair amount of milky run off...each subsequent clean will improve it to point it should stop dripping onto yours. Give it 3-4 cleans that should do it , then just include part of the regular maintenance

Thank you everyone for your responses.

I've had my window cleaner come and clean the windows and noticed pools of white water on the floor, what would this be?

They also claimed that they clean the windows regularly on a bi-monthly basis.

They have also tried to claim that the white marks was dust from construction works of a building over a kilometer away. Although I tried telling them it was pvc, they refused to believe that

That's definitely the PVC breaking down and the top layer getting washed off. It happens on painted garage doors as well.

You can get stuff coming from the vents but after a few cleans it disappears. I left white streaks all over my customers windows but that was degreaser that was on my brush I later found out. If they are old pvc windows then its just the pvc degrading from sunlight and acid rain. It can be limescale if the marks are permanent on the glass and then you need Kilrock, Viakal or white vinegar to remove it. ?

Part Timer said:

That's definitely the PVC breaking down and the top layer getting washed off. It happens on painted garage doors as well.

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Thank you, I did think so as I had that chalky like substance on my hand after wiping them.

scottish cleaning service said:

You can get stuff coming from the vents but after a few cleans it disappears. I left white streaks all over my customers windows but that was degreaser that was on my brush I later found out. If they are old pvc windows then its just the pvc degrading from sunlight and acid rain. It can be limescale if the marks are permanent on the glass and then you need Kilrock, Viakal or white vinegar to remove it. ?

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They are fairly old windows and are facing the sun. It did wash out quite a bit after this last clean. 

NoName said:

Everyday...get your /a local (pure water using) window cleaner to clean the upvc above when they clean your windows....initial clean of upvc will generate a fair amount of milky run off...each subsequent clean will improve it to point it should stop dripping onto yours. Give it 3-4 cleans that should do it , then just include part of the regular maintenance

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You have mentioned that after a few cleans, this should stop showing. The cleaners have claimed that it is done every 2 months, so is it likely that the windows have not been cleaned, or not cleaned/rinsed properly if this is the case?

Pjj said:

Are you sure they arnt between the pains of glass .? White streaks quite often happen like this when the seals on the glassing unit break down allowing damp in between the pains 

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Great answer. When the inert gas which is commonly nitrogen leaks out the capillary force between the pains creates condensation and causes milky water Mark's which look awful. Something to be mindful of when meeting new customers and explaining you can't polish a turd 

Apw1210 said:

Great answer. When the inert gas which is commonly nitrogen leaks out the capillary force between the pains creates condensation and causes milky water Mark's which look awful. Something to be mindful of when meeting new customers and explaining you can't polish a turd 

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This has happened too. But these marks I'm referring to were definitely on the outside and looked so much better after the clean I just had. They've not completely disappeared but somewhat better

Apw1210 said:

Great answer. When the inert gas which is commonly nitrogen leaks out the capillary force between the pains creates condensation and causes milky water Mark's which look awful. Something to be mindful of when meeting new customers and explaining you can't polish a turd 

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Quite agree I always point out potential issues like this and existing damage to glass and frames ,