This has been known about for at least 200 years and is referenced in many books , my grandfather was a herbalist-tobacconist , and used to make and distribute cigarettes, pipe tobacco and cigars which he produced in his own workshop and sold in the shop , he had an extensive library and he both let me read and showed me how it was done obviously , on a much smaller scale . Now this process applies to all types of Tabacco , cigarettes, pipe, and cigars . Whilst it was well known that washing the leaves in a water bath (3 day soak) drain and repeat twice , so a total of nine days , reduced the nicotine content almost to zero , it also effected the flavour , so they experimented a lot, could they add the nicotine back , so the Oil of Havana as per Bentleys was used , vinegar and more importantly the tannic acid it contained seemed a better substitute , so sour red wine (high tannin content) glycerin ( to ’fix’ the tannin onto the leaves) was used, the solution strength determined how much the nicotine strength was reduced , I don’t have the reference books , but I do have access to his shop index , which does have a smaller scale three ingredients mix you can spray on , distilled water, tannin powder and glycerin. I can’t remember the quantities off hand , but I do have them , I shall dig them out and add them here later.