Wooden window restoration – practical tips and recommendations
We know that many of you appreciate the quality and value of historic wooden windows, which offer a unique aesthetic experience and ensure a healthy indoor climate. 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. Each step is accompanied by 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 are stripped of old paint, they need to be treated with cold-pressed linseed oil, heated to approximately 60 °C. Apply it twice, allowing each layer to fully absorb and dry. Once 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 flexibility and longevity.
Next, you can focus on preparing the glass. Not all of you will do this yourself. This video shows just one of the glass cutting techniques, as each craftsman has their unique approach.
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🔧 Step 2 — Applying the putty
Once the shellac in the window grooves is completely dry, it's time to apply the putty. The putty needs to be thoroughly kneaded before use to become soft, uniform, and elastic. This ensures that the putty adheres easily to both the glass and the wooden frame, and does not crack during drying.
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🪟 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 splinters, or even glass strips for this purpose.
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🖐️ 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'll see a technique where the putty is worked in with palm movements — achieving particularly 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.
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🔪 Step 5 — Smoothing the putty
To smooth the putty, you can use a special putty knife or a simple flat chisel. 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 ensuring water runoff.
❗️ Make sure there are no air gaps between the glass and the putty — these can cause condensation and shorten the window's lifespan.
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🎨 Step 6 — Painting with linseed oil paint
The putty should be painted either within 24 hours of application or after waiting 3–4 weeks until it is completely dry and hardened.
During the first 24 hours, the putty is still flexible, and the linseed oil paint can deeply penetrate its surface, creating a hermetic and durable coating. However, if the paint is applied during the putty's drying period (within the next 3 weeks after application), it can cause micro-cracks in the paint coating, as the putty continues to release oil and excess moisture.
- The paint should be applied approximately 2 mm over the glass and putty junction to create complete hermeticity and protect the putty from rain and UV rays.
- To facilitate glass cleaning after painting, you can use fine chalk, which absorbs fats and oils. The best approach is to let the linseed oil stains dry, and gently clean them with a window cleaner only after the paint is completely dry.
We also recommend adding the natural mineral additive zinc oxide to the linseed oil paint to ensure an even more sustainable and durable coating in the harshest weather conditions.
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Good luck with your restoration work! For more information about our products for window restoration, you can find it in the section - Window and Door Restoration