Patination is a chemical process, whereby a minute layer of surface metal is converted into insoluble compounds, oxides, chlorides, carbonates, sulphides etc dependent upon the environment to which the coin is exposed. Normally this will be a slow, multifactorial process under influence of sweat, water, oils,salts, air pollutants eg sulphides, carbonic acid and I am sure a multitude of other chemicals, and variety of temperatures. The main difference with artificial patination is that the variety of active chemicals is reduced, but the process can be speeded up by increased chemical concentrations and temperature. Liver of Sulphur may certainly be one toning chemical available, there will be others. I have only used it on a couple of coins, pics attached. The chemicals do seem to reduce the gloss of a polished coin, as does prolonged boiling in rainwater. The polished coin needs washing, and de-greasing first (acetone, petrol) to encourage even toning. I tried using the L of S solution hot initially, but the tone was too dark too quickly (see the 1863 penny), but later experimented with a weaker, cooler solution and more prolonged exposure (see the 1874, unfortunately didnt take a 'before' pic. Neither is perfect, but with more practice a satisfactory tone should be possible, certainly both look better than they did. I would hasten to add that this is a 'last resort' measure for coins otherwise beyond redemption! Jerry