Mending the window putty


Until the 1970s, windows that are sealed with window putty were a matter of course. Since then, there are fewer and fewer such windows. Therefore, many residents and homeowners of a historic building do not always know how to repair window putty. Below we have summarized how you can repair window putty.

General information about window putty

Window putty has been used for several hundred years. It is a product that consists of around 85 percent whitewash (calcium carbonate) and 15 percent linseed oil varnish. Window putty is known by the following designations:

  • putty
  • putty,
  • Glass or glaze putty

Window putty is kept airtight. Before processing, it should be kneaded well, so that it is soft and supple again (similar to plasticine for children). If necessary, you can add a dash of salad oil already slightly dried glaze putty and then knead.

Why window putty hardens over time

In the air, so also in the window fold, it then comes to an oxidation. As a result, the Leinölkitt hardens and becomes hard as well as brittle. The putty then begins to crumble more and more. If the window putty is so damaged in only a few places, it is sufficient to repair the putty.

Repair the window putty

For this you should remove the window putty around the damaged area generously. Preferably, heat the glaze putty with an infrared heater. Although a Heißluftföhn would go too, but there is a high risk that the glass gets too hot and breaks. Especially with window glass with a maximum thickness of 3 mm there is a high risk.

After you have scraped out the window putty with a suitable spatula, generously paint the area including the wood of the window frame with linseed oil varnish. The more the wood absorbs the varnish, the more you paint. Now you can take the prepared new window putty, form it into a long caterpillar and press it into fold. You can also use a putty knife.

Further processing of the repaired windows

The putty must always be shaped so that rainwater (outside) and condensation (inside) can run well. Now the new window putty needs at least seven to ten days to dry. Depending on weather conditions, it may take up to three months for the window putty to harden well. Only now you can paint the window putty. It makes sense to paint the window putty before painting with paint (based on linseed oil) beforehand with linseed oil.

Tips & Tricks

However, if the damaged areas are too large and too frequent, consider replacing the entire window putty. Finally, the window putty takes on an important task and also insulates the windows.


Video Board: How to apply window putty