Hi all,

In Resene ColorShop, they told me that when painting over exterior glazing putty, the paint should be overlapped 1-2mm onto the window glass. This makes complete sense, since it will seal the gap and prevent water getting into the window frame. My problem is I can't get the paint to stay stuck to the glass. On windows exposed to rain, the paint will eventually flake away from the glass (see photo below). It's not just one window, it happens on every external window around the house. It was also like this when I brought the house, which indicates previous owners had the same issue.

This is the process I've followed and is what Resene suggested:

 

1. Clean the glass very well using isopropyl alcohol, let it dry for 1 hour, clean again with microfiber cloth
2. Paint glazing putty with Resene oil based enamel undercoat and overlap this 1-2mm onto window glass (the glazing putty is oil based)
3. Repeat step 2, but this time use Resene quick dry waterborne undercoat
4. Repeat step 2, but this time use Resene lustacryl semi-gloss waterborne enamel (top coat)

So that's three coats, all overlapped roughly 1-2mm onto the window glass. This eventually failed on every window where I followed this process - the paint eventually flaked away from the glass.

I have also experimented with only overlapping the topcoat (Resene Lustacryl) directly onto the window glass 1-2mm. It also eventually ends up flaking away, usually after rain. As above, I was very careful to clean the glass properly beforehand. Resene Lustacryl is advertised as suitable for exterior use, so I don't think that's the issue. I've had no issues with it on the window frames, just the window glass. Also worth mentioning the window frames are otherwise watertight, meaning this most likely isn't an issue with damp wood in the window frames.

Does anyone know what I can do to prevent the paint flaking away from the glass? Thanks!

Example of paint flaking away from window glass (I was not responsible for the scratched glass!):