 |
Home >>Brushes>>Paint Main Page
Gold Size and Black Varnishes(Japans)
Gold Size is a varnish-like material, used as a mordant, or adhesive, for gold leaf, or as a medium for certain classes of primers and fillers.It is made with a comparatively small proportion of oil, a high percentage of resin, driers, and volatile thinner.
It has excellent binding properties and, as it dries rapidly, is extensively employed for quick-drying finishes which are not required to have much durability.
Black Varnishes (Japans) This is a generic name given to a range of finishes prepared by adding various grades of bitumen to heat-treated oil, with the necessary driers, and, after cooling, volatile thinners.
In the best-quality black japan, a proportion of resin is included, to produce a harder, stronger, and more lustrous film.
Many different grades of asphalts and pitches are employed for the cheaper black varnishes, an inferior variety being Brunswick black, which is sometimes wilfully or inadvertently sold as black japan.
Apart from the question of durability, in which black japan is greatly superior, an important difference is that Brunswick black will " bleed through" and discolour a white or pale-coloured paint applied on top of it,
whereas black japan is, or should be, immune from this defect.
Black japan is not always easy to apply owing to the difficulty of determining when it is completely dry.
It may be quite dry to the touch but still soft underneath, with the result that freshly applied varnish will soften it up and give it a greenish tinge instead of the dense-black appearance which it should possess.
The best method of ensuring a really good finish in black japan work is to allow as much time as possible between coats.
Associated Pages: xxxxx VarnishessxxxxxxResinsxxxxxxLaquersxxxxxxGums