Modern dial salts are very mean with the sliver and leave a stainless steel, or burnished aluminium [sunburst] look. Which is completely and utterly wrong on an antique dial! So avoid eBay or Meadows and Passmore's "finest" silvering salts if you are not to be sorely disappointed! Or instantly recognized as a clock botcher [never bodger] by any self-respecting clock restorer!
I have silvered dozens of antique, brass, clock dials myself so know the difference. The proper white salts are still obtainable and are head and shoulders above the modern stuff. I have both kinds in in my cupboard and enough self-respect to know which is which.
Note that a matt white dial drastically improves legibility of the digits, clock hands and any engraving on a brass dial. They literally jump out at you compared with modern, shiny and silvery finishes. Which greatly reduce legibility. Even by adequate, artificial light the time is hard to read. Try reading it with a torch or candle!
Avoid the nasty, modern silver salts like the plague as they do produce a horrible shine which is highly undesirable. There should be no shine at all on a properly silvered dial! This is quite deliberate.
Matt white looks instantly and magically gorgeous during the silvering process. Which was perfected centuries ago when light, after dark, was in very poor supply. The only clock in the house usually had to be legible with just a distant and sputtering candle or taper. Or the cows would not get milked. Nor the household fires lit and the horses harnessed. These were vitally important matters at the time. An hour, in the pitch dark, is a very long time between the regular, hourly strikes of a clock's bell.
Silvering is a simple enough task with the required salts and only involves wet rubbing of the brass with fine emery paper to clean back to bright brass. This is known as graining and coarse abrasives must be avoided at all costs or the dial markings will soon disappear completely!
Try selling your Tompion without a signature or its exquisite dial markings! I have even seen early 18th century clock dials in historical period TV programmes with shiny dials. They might as well have put a baseball cap on the heroine! 😲 Even stately homes and museums have had their valuable clock dials brightly silvered by a Meadows & Passmore wielding vandal!
Graining is often accomplished with a manual, rotary action involving a block [for the 400 grade emery paper with a couple of drawing pins for security] on a simple arm with central pivot. The dial is usually supported on a heavily drilled board to allow the dial feet to sink. Allowing the dial to lie flat and stable as the block is rotated back and forth. The block, or pivot radius must be adjusted to match the dial size. Easily managed with a series of drilled holes. The emery paper must be lifted clear when finished with the graining or smudging of the circular grain will easily occur. Vertically graining a one piece, regulator dial requires lots of patience!
Graining is immediately followed by rinsing well under the cold tap and then cleaned off with bare, wet fingers but not dried.
This is quickly followed by damp rubbing with the correct [white] silver salts using one's bare [and perfectly clean] finger tips. Small cuts may sting but I have never been poisoned by the silvering process.
The silver should soon appear as a rather dirty but solid white and should be rinsed off only when satisfied a good and even coat is in place. If not, add more silver salts and rub some more with clean bare finger tips.
Note that each stage ensures the fingers/hands never dry off so they never have a chance to get greasy. Silver will only adhere to perfectly clean metal. So finger prints will show up if allowed to spoil the clean, wet brass.
The silvering stage is finally neutralized and whitened further with household Cream of Tartar rubbed on damp over the silver coating. Followed by plenty of rinsing. I found some finishing powders shine far too much when I was re-silvering antique clock dials. Modern and unnecessarily expensive finishing powders will easily spoil even the correct white silver salts! Buy Cream of Tartar powder cheaply from the supermarket instead.
Clear lacquering is normal for dials which are regularly handled for resetting to time. The problem is the wax filling in the engraving can become dissolved by the lacquer's own solvents. So that they later bleed dark marks into the silver. If you keep your fingers well clear the bare silver dial should last quite a while.
Re-waxing the engravings of a brass dial or chapter ring is quite another matter and should not concern the WT owner needing a simple dial 'freshening.'
BTW: Avoid heating any antique brass dial unduly. They tend to off-gas which used to be highly toxic when I still worked on lots of clocks. Overheating caused instant asthma for me. Though I do not normally suffer from asthma, at all. Interestingly [?] WD40 has very similar toxic effects on me but many swear by it. It puts me in bed to recover if I so much as get a whiff of the stuff.
There is a tradition that antique brass dials are not cleaned on the back as if it added some 'hazy' authenticity to the countless "marriages" purveyed by many, [antique dealer] criminal classes. I did plenty of work for a major, if local, clock specialist. Who would regularly play mix n'match with longcase weights and pendulums entirely at his personal whim just to make a few pounds more. I was expected to make them fit somehow until I grew tired of his corruption, greed and idiocy. I called a halt when he demanded dials were swapped with movements. A so-called marriage. Easily done but it requires new holes are formed for the dial feet and the old ones disguised with brass disks hammered in.