Indigo:natural versus synthetic

Leena has just pointed me to a site that aims to explain the difference between synthetic and natural indigotin( commonly called indigo). This is an translation of a Japanese paper and in summary say that while the synthetically derived Ai ( Japanese Indigo) is chemically the same as natural ai the bonds between the natural are shorter. Someone adding acomment says that the natural ai aggregates. This has an impact on the way it behaves while bonding to textiles and means that natural ai bonds better , is less likely to be washed off and less likely I think to crock. Interesting piece of research!