What is vinyl record dehorning and why are stampers polished?

What causes vinyl record horns?

When cutting a record onto lacquer, the base material on both sides of the heated stylus becomes soft and raised at the groove's edge, like passing a hot knife through butter. The material solidifies when cooling, leaving a ridge at the upper edge of the groove. This ridge is referred to as horn and contains sound information. Depending on how stable or unstable the ridge is, it can begin to break off, crumble, fray, or simply bend. Sometimes, even minimal contact – such as pulling the record out of its inner sleeve – can cause a change in the horn, which is even more pronounced if, for instance, the material of the inner sleeve is coarse. A record will always have areas where the horn is stable and others where it is unstable.

Physical impact on the horn will produce different visual and cosmetic effects: some records may show thin streaks, others may appear oily because the physical distortion of the horn refracts light differently. If small particles detach from the vinyl, while pulling the record out of a sleeve for instance, they won't damage the groove as they are the same material. Similar to how one fingernail cannot scratch another. Damaging the horn can however lead to distorting the recording's sound. Microscopically small bends or breaks, for example, can cause crackling and grinding noises but fortunately this occurs infrequently.

Preventing horns from forming.

To avoid horns, some pressing plants cautiously polish the mothers, essentially sanding down the horn. This process of polishing is known as dehorning. The quality of the finished record is totally dependent on how carefully this dehorning process is executed. Many newer, particularly smaller pressing plants that have opened in recent years, don’t polish because they lack the necessary know-how. They usually lack their own electroplating department and polishing and re-polishing would drastically delay production, as new stampers may need to be ordered and shipped repeatedly.

Visible imperfections resulting from inconsistently polished stampers or no polishing at all, can appear on the record as either oily sheen or hairline scratches which are not audible. Both are a sign of the mother stamper not being polished before pressing the records. Generally, these records play flawlessly, yet sometimes they exhibit a slight, static crackling noise, which disappears after cleaning or several playback sessions. This crackling is the result of loose vinyl particles in the groove that crumble off the groove's edge.

Direct Metal Mastering

Some plants primarily handle DMM (Direct Metal Mastering) cuts, where this effect is rare and has a minimal effect when it does occur. The majority of our cuts at Breed Media are DMM! At the Making Vinyl Conference in June 2023 it revealed that globally more than a hundred new pressing plants have opened in the last two years alone. It is assumed that most of these manufacturers do not polish, hence it's expected that the number of records with an oily shimmer or fine streaks will increase. As a customer, when assessing a newly purchased record with streaks or an oily sheen, it is advisable to listen first before lodging a complaint. Streaks or sheen can be caused by a range of factors so provided it plays without significant crackling after several plays or cleaning, the record should be deemed okay.

Whilst it’s unlikely you will experience streaks or oily sheen on your pressing, if you are concerned then you should consider avoiding inner sleeves made from plain paper. Polylined inner sleeves significantly reduce this problem and should become your standard.