Workshop Hints
Porcelain Dials

The British Horological Institute has archived and edited the following from e-mails sent to the Clock/Clockers mailing lists on the Internet. The information here does not necessarily indicate a method approved by the BHI, we are only publishing this digest so that others can decide for themselves whether the methods listed below will suit them.

From: Richard Corfield, Richard Lowe, Rob Beaver, Harry Gilmore, Eliot Isaacs FBHI, Mel Kaye

Cleaning

Here's a recipe that I use.

1. mix a 5 per cent bleach solution in ordinary tap water
2. add a sprinkling of shirt collar stain remover (i.e. surfactant)
3. slip the dial into the solution
4. put the jar containing the solution into a bigger jar of hot water.

The solution in the inner jar warms up gradually and expands the dial slightly, the surfactant loosens the dirt and verdigris, the bleach digests it. Bingo!
You can additionally ultrasonic the mix if you want but I find that this can ruin dials.
Finally, caution, this solution is not stuff that you want on your hands or to accidentally ingest.

Repairing

When a dial gets badly cracked or chipped, it can be repaired. The following are some suggestions on techniques etc. In repairing a chipped porcelain dial, there are two problems to overcome:

1. To fill in the "hole" left by the missing porcelain, so the surface is uniform & smooth.
2. To make the patch match the colour and gloss of the porcelain dial.

The Do-it-yourself approach can be undertaken several ways,

• The "traditional" method is filling with hard white wax, but I've never been really satisfied with this. If numerals have to be added, drawing on the wax is very difficult. And the surface has a tendency to accumulate dirt which cannot be cleaned off.
• There is a two-part fine grain white epoxy putty. The brand available in the UK is called Milliput (Superfine White grade), made by
  The Milliput Co., The Marian, Dolgellau, Mid Wales, LL40 1UU, U K Tel 01341 422562.
  It is a bit messy to at the start as the two parts have to be kneaded together until they are fully blended, but one considerable advantage is that it can be applied and smoothed off with a damp knife. I found it a good match for the French dials that I used it on and of course the end result is hard.
• Another is to find a proprietary porcelain paint. This is a thick stringy material which has some bulk, and can be built up in several layers if necessary, and self-levels fairly well to a shiny finish. You can apply repetitive coats, until the thickness matches the surrounding porcelain. If the colour is not close enough, you can add smidgens of tinting colours (from your paint store) to each application.(Add the colour to a little puddle of lacquer on a glass plate) so that by the time you have built up the thickness to where it belongs, you also have a good colour match. The tinting colours you may need will be blue, yellow, black, and maybe red. Remember to let the application dry before you check the colour.
  If you overlap onto the porcelain, let it dry thoroughly and then do a little discrete razor trimming. If the lacquer gets too thick, it will start to get stringy. If this is a problem, add a little acrylic reducer (probably xylol or toluol).
• A complete kit of all the items for porcelain dial repair is available in the UK from Horological Solvents Ltd., Proctor Street, Bury, Lancs BL8 2NY, United Kingdom. Phone 44 1617 642741 Fax 44 1617 648696
  It contains a two part epoxy resin, white filler powder (kaolin), three tinting colour pigment powders, numeral ink & pen, abrasive papers, clear glaze and tools for mixing. It does all it claims to do, BUT there is still a lot of personal skill involved in matching the colour of the original dial exactly.

 

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