When I want really dark sights on pistols at range, I use Anschutz Black Match - lighter with special fuel. But it is temporary darkening at it is easily removed.

But when carry pistol for self defense, removing from holster etc., gun sights will get soon or later "polished". So what is the best product for permanent darkening iron sights? I tried few "cold bluing" liquids and gels, but what I found it is not lustreless at all and it's resistance is not good.

Jiri

Cold blue is not much good. For really, really, really black heat the sight over a gas flame and then dunk in old engine oil. The more carbon in it the better.

Return the thing with the oil still dripping on it to the flame. It will "blaze" as the flame ignites the now heated oil.

Repeat and repeat. This will give you a durable deep jet black. No need at all for the sight to be red hot. In fact it should not be. Just hot enough that when plunged into the oil for a second the oil fizzes as it goes in.

Like when you put a hot skillet under the cold water tap after frying bacon.

Now one warning. If you sights aren't steel but anodised black aluminium you'll remove the anodising and turn them a bronze colour!

Experiment with a steel off cut the same size as your sight. Try a plain steel nut for example.

Thanks for advice. I will think about that.

Jiri