Double gilding outdoors – is double made always better?
Should you opt for simple gilding or are you better off with double oil gilding? Gilders, architects and builders have been debating this question for years. To begin with: a well-executed gilding should last for around 25 years outside without mechanical contact from human hands. So what might cause gilding to have a shorter lifespan outside?
Factors affecting the durability of gilding
The most important criterium for the durability of gilding is the surface. In most cases, outdoor gilding is carried out under time pressure (e.g. weathercocks, church steeples, tower crosses or similar). Only a well dried and outgassed surface (varnish) can offer long-lasting gilding. Varnishes emit gases for several months before they can be considered stable. The applied adhesive (Mixtion) acts as a barrier layer and is intensively attacked by a “gas mixture” if the paint substrate is not outgassed. The result is a compromised durability and a significantly shorter lifespan of the gilding work, as the Mixtion loses its adhesive power and the gold leaf can be washed away by rain.
Another problem is presented by thick Mixtion/adhesive layers. The adhesive is flexible, in order to balance out temperature fluctuations. If the adhesive layer is applied too thickly, we will ultimately be gilding on a soft underground that can easily suffer mechanical damage. The result is visible: the gilding remains matte and the surface scratches easily. If a second and third layer of adhesive are now applied to this first soft layer, the problem is only exacerbated. A bird landing on this surface will scratch it with its claws down to the paint layer. Bird droppings, diluted with water, then find their way under the first Mixtion adhesive layer. The result: the gilding simply peels away from the surface.
Every outdoor surface/object should be tested for the best gilding technique. We recommend using thicker gold leaf to gild sides that will be exposed to extreme weather conditions. For restoration projects, the condition and degree of weathering of the original gilding should be assessed first of all by visual inspection, before planning for a new gilding procedure.