HOGHAIR - the best example is the so called 100% interlocked hoghair blue handle Neef 1150.
Probably 90% of oil painting would be done with hoghair.
This bristle leaves brush marks in the paint film where required and only the best quality Chunking bristles are selected. An extra length of hair is inserted into the ferrule formed into a mould and oven heated for a short time, giving the bristles greater spring. All of this quality control enables the interlocked bristle to retain its shape and resilience over many years.