What do white, blue and sun-dried sulfuric acid mean respectively?

A white picture refers to a white paper that is directly printed or bound into a book. Generally, most design institutes now use white drawings to draw pictures.

Blueprints and sulfuric acid diagrams are old drawing methods. The specific method is to draw a picture with sulfuric acid paper first, that is, sulfuric acid diagram. This picture is the base map. When the sun needs to be added, sulfuric acid and the sun are used as blueprints. This method is an old one, but it is not adopted by most design institutes because of its low drawing efficiency. But there are also some design institutes in use.

Sun-drying sulfuric acid diagram refers to adding sun-drying blueprint with sulfuric acid diagram.

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