Dial resilvering

[mbhorology]

For my BHI Record of Repairs one of the operations I need to carry out is re-silvering a dial.  I've seen this kit from cousins and wondered if this contains everything I need to try this process out?

https://www.cousinsuk.com/product/dial-silvering-kit?code=S1526

I understand that I'll need very fine abrasives to remove the old silvering back to the original brass, then use the items in this kit. 

Thanks

[oldhippy]

What type of dial do you intend to re-silver. It looks like the sort of kit I have used for silvering Longcase clock dials.

[mbhorology]

Yes it would be for a longcase clock dial.  This is the tick in the box I'm hoping to achieve at least for by BHI work.

As a sideline I'd also like to experiment with etching my own dials and silvering them too.  Maybe starting with a large calibre watch (6497).

[oldhippy]

You need to make sure the dial is absolutely clean, free from dust and tiny hairs. There is everything you need in the kit. The lacquer dries very quickly. I used a very fine artist brush so as not to leave any marks.  Re-silvering is not hard to do.

Good luck. Any chance of before and after photos. 

[clockboy]

I recently re-silvered a dial and the key I found was to have the the dial absolutely clean and absolutely grease free. After using wet & dry to remove the old silver I used methylated sprits to clean the dial. However the issue for me was how to re-paint the face. I have no artistic skills whatsoever so I used a clear dial water transfer. After many experiments the best transfer was from Meadows & Passmore  but pricey. 

[mbhorology]

Thanks for replies.  I'll certainly post pictures before, after and during the process which may help others in the future.

[wls1971]

Its a easy process just as long as everything is clean you just rub a small amount of silvering powder on with a slightly damp cotton cloth, the hardest part if it needs doing  is filling the engravings with engravers wax which is actually a stick of black shellac you would require a small spirit burner to do that, you heat the engravings from below and rub the wax on the engraving whilst hot to melt the shellac into the recesses, you then have to leave it to cool and go solid and then scrape of the excess this has to be done before the silvering process, and the dial would require rubbing down again to take it back to brass, once re silvered if the engraved numerals look dull you can gently heat again from below to remelt the shellac that would make them look nice and glossy. I have given up trying to brush on shellac lacquers I have a small air compressor and air brush which I use.

 

[mbhorology]

Finally tried out the operation this afternoon.  First photograph shows the dial with brass showing through the silvered section.

 

It was rubbed back with 1200 on a flat block to brass.  The numerals didn't need any extra work to refill so it was just a case of silvering the cleaned brass.

 

Using a damp cloth (wearing gloves as I've no idea what the chemicals are) I rubbed in small amounts of Horosilv.  It takes a while and initially you think nothing is happening, but gradually it turns silver and you need to work it all over to get a consistent finish.  You then wash it in clean water.

Next you repeat the operation with Horofinish again applying small quantities and rubbing it even into the dial.

Again you clean in clean water before drying and applying the lacquer which smells pretty bad!  

I'm very pleased with the end result so thanks again for the guidance on this.

Out of interest does anyone know what the white powders are?  I'd be interested to understand the chemical reaction and what I've been working with other than Horosilv and Horofinish magic white powders.

Edited December 16, 2018 by mbhorology

[nickelsilver]

There are numerous formulas in old horological texts, but the simplest I've found (and use) is by weight: 1 part silver nitrate, 2 parts table salt, and 2-3 parts cream of tartar (potassium bitartrate). These get mixed up and stored in a glass container, brown preferably, and kept from light. I mix them with a mortar and pestle to get the particle sizes fairly uniform. Some formulas call for silver chloride, but that is what you make when you wet the silver nitrate and salt.

I don't know what the commercial finishing powders are but with the above formula you wash off the remaining silvering paste with water, then rub down with straight cream of tartar, rinse again dry and lacquer.

I also don't know what the exact reaction is that gets the silver to "stick". I do know that if you keep going the silver layer can get quite thick and will eventually flake off.

Edited December 16, 2018 by nickelsilver

[nickelsilver]

Well it didn't take much digging to figure out how it works (and I've wondered for years!). The copper in the brass reacts with the silver creating in essence a battery. A tiny bit of the copper is dissolved at the same time the silver plates out of the nitrate solution. The "battery" dies when all the brass is covered.

Which raises the question of how I managed to get thick deposits which flaked off... though at the time I was doing a lot of experimenting with different proportions of the 3 ingredients.

[oldhippy]

When you are rubbing down the dial, you must always work in one direction. If you do not you will have very nasty marks and the dial will look terrible.

That’s a very nice bit of work.