Case Hardening was developed many yars ago to put a hard surface (Case) on low carbon steel or iron which would not harden by the heat & quench method of higher carbon steel. Without going into a lot of detail when the steel was heated above its critical temperature & held for a period of time in a carbon atmosphere the carbon was absorbed into the surface of the steel. A quench then would harden the higher carbon surface (Case) but not the inner core which was still of a low carbon content. The technical term for this is Carburizing & hardening. It generally became known as case hardening & when done with color Color Case Hardening. The nice colors were actually a by product of the process normally occurring when Animal charcoal was used for the carbon source. Alloy steels containing more than about 20 points (.02%) carbon are not normally carburized but heat treated which does not produce color. Several makers of modern guns have developed methods of producing some color on their gun parts which are not true "Color Case Hardening" but simply a chemical color process.
Back at the point in time Ithaca was importing the Perazzis, these guns receivers were made of an alloy steel which was heat-treated & subsequently "Colored". Ithaca published in a gunsmith manual they put out their recommended procedure for "Re-Coloring" one of these. It consisted of; Heating the part "Evenly" with a "Torch" to about 200°F or until it would just start to sizzle a dab of water. A Q-Tip wasa then dipped in cold bluing solution & dabbed, sprinkled or streaked on. They then recommended a coat of clear acrylic to protect the colors. Ithaca recommended 44-40 blue, I have tried Brownell's Oxpho & could tell no difference.
Several things of note;
1st - an most important, this method should never be confused with the process of holding the tip of a torch in one spot on a part which has previously been hardened by any method, either case or through, until the part takes on a "Temper Color".
2nd - This method in no way heats the part any hotter than a boiling water bath of a rust blue & definitely not as hot as a Sale Blue bath. this process in no way damages any previously imparted heat treatment it may have received. The colors produced are very thin & if un-pleasing can simply be poilshed off.
3rd - This will "Never" produce the colors of a true Bone Charcaol Color Case Hardening. But at a cost of about $5.00 as opposed to the price of a Bone hardening job it has its place.
I personally would not care to spend $300.00-$500.00 on a gun which would be Worth about $250.00 when it was finished. Whether or not is is preferable to simply leaving it worn, rusty or shiny is purely up to the individual owner. Actually with a bit of practise one can produce a finiash which to me is about as attractive as the average Cyanide finish.
