This initially formed ripples on the surface. Excess was sometimes wiped off by a blade, skimming and smoothing the surface. Not high speed air flow is much more efficient. Tandem coating refers to a two stage process that coats both sides of the paper sheet. Coaters apply separate coatings to paper after the paper sheet has been formed and dried.
Coatings are substabces put on a finished sheet of paper.
They are made in what is called color kitchens. Coaters can make a paper protected or shining, like magazine paper. More than one coater can be used. A sheet can be coated with a solution that includes pressure rupturable materials, or tiny capsules that rupture when put under pressure. An example is carbonless paper.