Oil on canvas with gilded areas – best practices

While we do not have direct experience with LeFranc and Bourgeois Mixtion, it is likely a high quality product; however it is also most likely to be intended for use on rigid supports as most oil sizes tend to form rather hard and brittle films. It is difficult to state whether one or two layers would be sufficient…this will likely have much to do with the composition, thickness, and absorbency of your ground and/or underlayers (are you gilding directly over oil paint?)….If you are working over an acrylic dispersion ground it may be better to use one of the water-born sizes (e.g. Aqua or Wonda size) as they will be more flexible. If you are working over a less absorbent oil ground/oil paint then it may be useful to first put down a thin layer of something more flexible like alkyd medium and let it dry before applying another thin layer of L&B size. As for the gold interacting with the oil paint you do not need to worry about this…be sure to check wether you are using ACTUAL gold leaf as there are many different alloys that are available today. It is the presence of copper, zinc, and other metals that tend to be more problematic in the long term; however, this is really only an issue if you do not coat the metal alloy to protect it from environmental pollutants and moisture (both can cause the alloy to tarnish). If you have are dealing with an alloy it is best to coat the leaf for this reason, even if you intend to glaze over the surface with oil colors. Realize that a matt picture varnish will cut the sheen of the gold, something you may or may not want. To preserve the sheen it is better to use a non-matte varnish. For true gold leaf it is really up to you whether or not you want to coat the surface. In either instance (true gold vs. alloy), glazing over the surface using thin applications of oil paint is also possible but be aware that you may undercut the oil-based size if you do not wait long enough or if you use too much diluent.