FAQs around technical topics

The roughness depth is a parameter for the roughness of a surface. It will usually be measured in microns.

In simple terms, roughness depth is the average difference between highest and lowest points in the measured (scanned) area on the surface of a profile.

The roughness of a surface determines its reflection of the light and thus the degree of gloss.

Gloss is the optical property of a surface to reflect light wholly or partly specularly. If a surface is not shiny because it diffusely reflects light, it is called dullness.

The unit in which gloss is measured is called GU (gloss units). GU is colloquially referred to as gloss level.

Gloss is measured with a gloss meter. On the basis of the measured GU, a distinction is made in high gloss, medium gloss and matt gloss, sometimes even being further divided into silky or satin matt.

Blowholes (or blisters) is a term from metallurgy and refers to a cavity formed during the solidification of cast parts. Often, cavities in the metal that have arisen in a different way are also (incorrectly) called blowholes.

Blowholes are a hallmark of defective material quality.

If blowholes are in the metal, they can also occur in the area of the surface. If such a surface is then treated, e.g. polished, the holes are opened. So, small cavities or craters, i.e. blowholes, appear on the surface.

If the whole metal is punctured by blowholes, a purposeful processing of the surface becomes impossible, since the treatment itself continously opens up new cavities.

A workpiece with blowholes can easily become scrap.