Primers

Primer is the layer with which wood is first treated before it is given a color. This used to be done to prevent the volatile components of paint from getting into the wood quickly and the paint therefore having poor adhesion. It also prevented that the grain was clearly visible due to the difference in the structure of the wood in the grain.

To paint metals, especially the metals on which an oxide layer is formed, an etching primer must be used, because paint, and certainly also ordinary primer, does not adhere well to the oxide layer. With steel it is virtually impossible to get good adhesion and an etcher primer is the only way to provide the steel with a good lacquer layer. The etching primer etches the oxide layer away and ensures a good transition layer from the steel to the paint.

An etcher primer therefore has no function on plastics and will generally also affect them. When dyeing zinc alloys, it is advisable to first test the applicability of an etching primer in a place that is not visible. Some etch primers are too aggressive for an application on zinc or tin. The material from which most scale models are made is ZAMAK, and abbreviation for Zinc Alluminium MAgnesium Copper. Although invisible, an oxide layer is also formed on ZAMAK. An etching primer is recommended, but not always necessary because the oxide layer also has good adhesion. A filling primer is recommended due to casting galls.