Wooden window restoration – practical tips and recommendations
We know that many of you appreciate the quality and value of historic wooden windows, which provide both a unique aesthetic experience and ensure a healthy indoor microclimate. Properly restored and maintained historic wooden windows can last for decades, even centuries.
In this article, we share our experience and practical tips on window restoration and renovation. For each step, we have included a video from Swedish window restoration master Peter Gantelius—one of the most recognized specialists in Scandinavia.
🔨 Step 1 — Preparing the window before glazing
Once the window frames have been cleaned of old paint, they must be treated with cold-pressed linseed oil, heated to about 60 °C. Apply it twice, allowing each layer to fully absorb and dry. When the linseed oil is completely dry, coat the inner grooves of the window with shellac—this prevents the wood from absorbing linseed oil from the glazing putty, ensuring the putty's elasticity and longevity.
Afterwards, you can proceed to preparing the glass. Not all of you will do this yourselves. This video shows only one of the glass cutting techniques, as each craftsman has their own unique approach.
Video:
🔧 Step 2 — Applying the putty
Once the shellac in the window grooves has completely dried, it is time to apply the putty. Putty must be thoroughly kneaded before use to make it soft, uniform, and elastic. This ensures that the putty easily adheres to both the glass and the wooden frame, and does not crack during drying.
Video:
🪟 Step 3 — securing the glass
At this stage, the glass pane is first secured with wedges or pins, and then, using fine headless nails, the pane is fixed to the window frame. Wedges provide stability for both the glass and the window sashes. Craftsmen often use matches, wooden splints, or even glass strips for this purpose.
Video:
🖐️ Step 4 — applying the putty
Some craftsmen apply the putty with a knife, while others form small “sausages” and press them in with their fingers. In this video, you will see a technique where the putty is worked in with palm movements — this ensures especially good adhesion to the glass and frame.
There is no single “correct” technique — the most important thing is to ensure that the putty adheres evenly and tightly to all contact points.
Video:
🔪 Step 5 — smoothing the putty
A special putty knife or a simple flat chisel can be used to smooth the putty. The goal is to achieve a smooth, even slope from the edge of the glass to the frame.
💡 The sloped edge of the putty should be wide enough to protect the glass from rain and UV rays, while also ensuring water runoff.
❗️ Make sure there are no air gaps between the glass and the putty — these can cause condensation and shorten the lifespan of the window.
Video:
🎨 Step 6 — painting with linseed oil paint
The putty should be painted either within 24 hours after application or you should wait 3–4 weeks until it is completely dry and hardened.
During the first 24 hours, the putty is still flexible, and linseed oil paint can deeply penetrate its surface, forming a hermetic and durable coating. However, if the paint is applied while the putty is drying (within the next 3 weeks after application), this may cause microcracks in the paint layer, as the putty continues to release oil and excess moisture.
- The paint should be applied about 2 mm over the joint between the glass and the putty to create a complete seal and protect the putty from rain and UV exposure.
- To make cleaning glass after painting easier, you can use fine chalk, which absorbs grease and oil. The best approach is to let the linseed oil stains dry and gently clean them with a window cleaner only after the paint has fully dried.
We also recommend adding the natural mineral additive zinc oxide to linseed oil paint to ensure an even more sustainable and durable coating in the harshest weather conditions.
Video:
Good luck with your restoration work! You can find more information about our products on our website.