How did the world's first coffee filter paper come from? What is the standard aperture of coffee filter paper?

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Which filter to choose for hand-brewed coffee: comparison of filter paper, metal filter mesh and filter cloth

More than 100 years ago, people used linen or metal mesh to filter coffee, which tasted bitter and coffee grounds often precipitated at the bottom of the cup, German mother Melita. Melitta Bentz, racked his brains to make a delicious cup of coffee.

One day she had an idea and poked several small holes in the bottom of the copper pot.

Then cut the paper of my son's workbook into a circle and put it inside the copper pot.

Unexpectedly, the filtering effect of this blotting paper is excellent, and the bitterness of the brewed coffee is greatly reduced.

As a result, the world's first filter paper and filter cup were born.

After several improvements, Melita was the first to apply for German patents on filter paper and filter cups in 1908, and the products developed were popular all over the world.

Technical index

The technical index of filter paper can be divided into two aspects, one is the filtration characteristics of filter paper, the other is the physical characteristics. Filtration characteristics include air permeability, air resistance, maximum pore diameter and average pore diameter. Physical properties include quantification, thickness, stiffness, corrugated depth, bursting resistance, resin content, etc.

Quantitative: refers to the quality of filter paper per square meter, unit: g/m2.

Thickness: refers to the thickness of the filter paper, excluding the corrugated depth. Unit: mm.

Air resistance: the resistance of filter paper to air flow. Expressed by the pressure drop of 100cm2 filter paper passing through 85 litres of air in one minute. Unit is mbar. Or water column height (mm).

Corrugated depth: the depth of the groove pressed to enhance the longitudinal stiffness of the filter paper, in mm. In general, its value is 0.2mm.

Air permeability: the amount of air passing through the filter paper per unit of time under a certain area and pressure (20 mm water column). The unit is L / m2 ·s.

Nominal filtering accuracy: refers to the ability of filter paper to retain particles of a certain size, and the particle size of a tiny sphere that can be retained or filtered out of 50% shall prevail. Unit: μ m.

Maximum aperture: the void size calculated from the pressure of the first bubble on the filter sample during the test. Unit: μ m.

Average pore size: the pore diameter calculated by the pressure during "dense" bubbling is called the average pore diameter. The unit is μ m.

Resin content: the percentage of resin in the weight of filter paper. Generally speaking, it is 10%, 30%, and 30%.

Stiffness: anti-deformation ability of filter paper. Unit: mg.

Bursting resistance: the maximum pressure that filter paper can bear per unit area. Unit: kPa.

Usage

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