The base material for black varnish can vary, depending on the desired quality and purpose of the varnish. One commonly used material is bitumen, which can be derived from petroleum, natural asphalts such as uintaite, or pitches from coal tar.
Petroleum bitumen is a popular choice due to its availability and cost-effectiveness. It is a byproduct of the petroleum refining process and can be refined further to obtain different grades of bitumen. This versatile material is widely used in various industries, including the production of black varnish.
Another natural material used in black varnish is uintaite, which is a type of natural asphalt. Uintaite is formed from the remains of ancient algae and organic matter, and it is found in specific regions, such as the Uinta Basin in the United States. It is known for its high carbon content and unique properties, making it suitable for use in varnishes.
Pitch, derived from coal tar, is also utilized in the production of black varnish. Coal tar is a byproduct of the coal carbonization process and can be distilled to obtain various substances, including pitch. Pitch is a thick, black, and sticky material that has adhesive properties and can provide a durable finish when used in varnishes.
For the production of high-quality black varnish, particularly in applications such as coachbuilders’ black japan, only the purest grades of asphalt or pitch are typically used. These pure grades are often combined with a hard gum, such as copal, to enhance the varnish’s durability and glossiness.
In terms of cost, Brunswick black varnish is considered the cheapest option. It is a solution of bitumen in white spirit. White spirit, also known as mineral spirits, is a petroleum-derived solvent that helps dissolve the bitumen and create a liquid varnish. While it may be the most economical choice, the quality and durability of Brunswick black varnish may not be as high as varnishes using purer grades of asphalt or pitch.
The base material for black varnish can vary depending on the desired properties, cost considerations, and specific application requirements. Petroleum bitumen, natural asphalts like uintaite, and pitches derived from coal tar are all commonly used materials in the production of black varnish.
