Earlier in the year I wrote a number of posts about the long, well-established tradition of painting the exterior of houses in the Nordic countries. On this trip I spent a day at Den Gamle By, the open air museum in Århus that opened in 1909 and which has a large number of urban buildings from all over Denmark that have been saved, dismantled and rebuilt there. Many of the rooms in the houses are appropriately furnished but some areas are used for good displays about aspects of trades, craftsmanship and building techniques. There is an interesting display in one house about paint and natural paint colours and about paint brushes and methods of painting with paints based on linseed oil.
Over the years I have done a fair bit of decorating and have reglazed several windows but at Den Gamle By I learnt that I had been doing it the wrong way. It is fairly obvious that glass is held in a rebate in the frame of the window with small wire nails that are carefully inserted to keep the glass firmly in place and then putty, again made from linseed oil, seals the external gap to keep out rain driven against the glass. So far so good. But I had assumed that the putty would adhere better to the timber of the rebate if the wood was left untreated. At the museum I learnt that, in fact, the frame should be painted first with several coats of paint, up to six coats, and then the glass is pinned in place and the external angles filled with putty. This is because untreated timber absorbs moisture from the putty and makes it crack and break away: sealing the wood first with paint means that the putty stays soft and flexible and therefore weather proof for much longer.