Varnished items from older collections.

[Shakethetrees]

Originally Posted by Battara

Be very careful with the niello - a type of oxidation easy to take off and not to place back on. In fact, I'm not sure if anyone does niello anymore since the chemical fumes are very toxic.

Niello is a horrible mix of lead, and a little copper. When it's thoroughly mixed and still completely molten, a handful of powdered sulfur is mixed in, stirred, and poured into long thin (1/4") strips and allowed to cool.

Once a decorative design is chiseled into a piece of metal, the metal is heated and the niello strip is "mushed" into the design leaving excess. Or, it can be ground into a fine powder and applied like vitreous enamel and then fired. Allow to cool, and file the excess away, using a coarse single cut file. It's like filing graphite, soft, with a tendency to chip if you rush it. Polish any file marks polish with emery.

I did some of this while a student forty years ago, under a laboratory vent hood, and, believe me, it's a smoky, sulphurous, stinking mess. Glad I did it once or twice, but I don't think I ever want to do it again.

There are many formulae recorded, each with slightly different compositions and working attributes coming from early sources from around the world, but, I post this here for reference and not as a recipe, so unless you have laboratory ventilation, don't do it.

If repairs are absolutely necessary I would look into using an epoxy based mixture instead.