The problem of veins can often be traced to poor preservation or in the case of fresh hides to holding too long without temporary preservation before processing. The vein material contains the protein elastin and this is very quick to degrade by bacterial action if not preserved or processed quickly enough.
The veins collapse leaving voids under the grain and producing the characteristic vein marks. Veins can also be made worse by soaking / liming at too high temperatures and without biocide. Pickling at too high temperatures can also cause vein problems.
Good practice: Chill goods immediately after flaying and process goods as soon as possible after flaying using ARACIT biocides. If short term storage of goods is necessary temporary preservation using ARACIT range products is recommended.