Silvering clock dials.
I have re-silvered/restored brass dials for over 20 years and heard so many tales about how poisonous the process can be and to use safety gear, gloves-goggles etc, that I thought it was time to set the record straight.
Yes, the compound is poisonous but only when ingested/eaten. It does not penetrate the skin and will sting if any cuts are present on your hands; I assume this is due to the salts in the compound.
It will not turn your hands brown/green or any other colour.
I have tried dial silvering using thin latex gloves and found that I lost any feel for the process, I also found that it used more silvering compound than using your bare hands.
Whichever way you choose, preparation and cleanliness is the key to successful silvering.
I have always done all the silvering jobs at the kitchen sink for one simple reason, it is so easy to clean the surfaces and move onto the next process, better still if you have a wet room in the workshop.
I will show 2 different silvering jobs as a guide to which to choose for different situations.
The first is a typical 18th century Longcase dial and the second is a new Merlin Band clock.
These two jobs at first sight might seem one and the same but an element of common sense has to be applied.
The Longcase dial has hand engraved numerals etc and is quite deep, it needs some form of black filler that has some body, and I chose the traditional wax filling for this job. I have on occasion used Araldite/epoxy mixed with a small amount of black cement powdered dye.
The main problem with wax is to find some covering that does not cause the wax to bleed into the surrounding dial, do a test with cellulose thinners and you will see what I mean.
I have done some experiments with the new breed of acrylic varnish and this has no effect on the waxed numerals.
The Merlin clock has etched numerals that are quite shallow and because the bands would present a problem with the hot wax method, I chose to use black acrylic car spray paint and cellulose lacquer.
A test piece showed that there was no reaction between these modern materials.
When working on old dials, I try my best to do the job first time with no mistakes.
This at first sight might seem a bit picky but on old dials we have to realise that each time a dial is silvered, a small amount of metal is removed from the surface.
Some dials have flowing engraving, birds, flowers and even signatures, these by their very nature are cut quite shallow, to rescue a bodged finish or mistake will remove more metal from the surface of the dial so try and do the job first time around.
Lets take on the old dial first, a typical Longcase job, the parts of the dial are removed and placed in the clock cleaner solution, this will dissolve the old wax in the numerals and remove some of the Verdi Gris.
The parts are scrubbed with a brass brush in the grain of the numerals; this should remove any remaining old wax and rinsed in clean water.
The rings are now ready for filling the numerals with new wax.
Use a gentle flame to heat the ring/dial and rub the wax stick over the surface, this is a tricky part of the process, you don’t want the wax to bubble, this will ruin its structure.
You can use a piece of card or a lollypop stick to spread the wax around to fill any gaps in the numerals and to remove the excess.
I have always used a large bench vice as a workstation for supporting a dial or chapter ring, this allows you to waft the flame from below the dial.
As an aid to better working, I wear a glove on my left hand and hold the torch with this hand, my right hand does the wax filling and spreading.
I only do a small portion of the dial at a time and then turn the dial around with my gloved hand.
Once all the engraved parts are filled, it’s off to the wet room (kitchen).
Because my kitchen is part of a family home, I clean all surfaces with washing up liquid and sluice down with plenty of water; I don’t want any grease or oil anywhere near, when silvering.
I fill the sink with about one inch of warm water and add a few drops of washing up liquid; this helps the wet or dry paper do its job.
I use a little scrubbing board for placing the parts I am working on; this saves the finish on the draining board and supports the work, which has any protrusions, dial feet etc.
Using w&d paper backed with a flat piece of cork, start to rub the wax and roughly follow the curve of the dial or chapter ring. Don’t press to hard as the paper will clog, let the paper do it’s work. When you feel that the paper has done its job, renew it; you will be wasting energy using clogged paper.
When all the wax has been removed and the brass surface is clean, it needs to be grained.
I have seen some good dials ruined because the repairman used a paper that was too coarse for the job.
I never use anything coarser than 400 w & d paper and that is what I used on the Longcase dial. I have read that graining can be done on the lathe faceplate but never tried it; I use a graining board and find I have complete control of the graining process, without fear of mishaps.
A graining board is just a flat piece of wood with a batten screwed underneath which is held in the bench vice. A central post is fixed which an arm is rotated around; the arm carries a cork pad, which supports the w & d paper.
At first sight, graining looks a very easy part of the job but as with most things, it has to be learnt.
Imagine a one piece silvered dial or a clock plate, these are normally grained top to bottom, to do the job successfully in the first place, it is necessary to find some way to hold the piece, you cannot lay the dial on the bench and hope to do a good job, it will tip up with the pressure and spoil the finish.
Support the piece on battens and clamp the front one to the bench; this will take the side forces when graining.
Wrap a piece of 400 paper around a flat cork block and start at the top, draw the paper down in one continuous motion until it has left the bottom edge, any hesitation will result in small swirls which will show on the finished dial.
The same will happen when graining circular pieces, the idea is to place the paper straight down with a confident manner and lift it off with the same purpose.
Once the graining has been done, do not touch the surface with your hands and slide the part out so you hold the underside or use gloves, take the piece to the wet room/kitchen and rinse off any abrasive used in the graining.
At this point I use washing up liquid to wash my hands, my reasoning is that the liquid will neutralize any oils in my hands and let me have enough time to do the job.
I use paper towels to remove most of the water from the brass parts and the draining board; you do not need lots of water when silvering.
I use both hands when silvering so that even the hand holding down the dial is playing its part in the silvering process.
Work around the dial and rub your hands/fingers in the direction of the graining, you want the solution to have the texture of thin soup.
Sometimes the brass looks as if it does not want to take the silvering, set the piece aside and start on another, the silver salts will still be doing their job.
Go back to the piece and it will start to turn a dirty grey colour, this is good and nothing to be worried about, when there are no more brass patches showing, it is time to rinse everything down for the final finishing powder.
As before, dry the parts until they are just damp and use the finishing powder in the same way, the dirty grey will transform before your eyes into that bright, silvered finish we know so well.
Rinse the parts thoroughly and dry with paper towels, I usually set aside the parts for about one week, place in a drawer or at least out of harms way.
Inspect the parts after the week and look for any blemishes or slight blooms that might have appeared; if there are none, then you can apply the lacquer/varnish of your choice. If there are any marks/blooms/blemishes present, then you will have to go through the silvering/finishing stages again.
The Merlin clock time bands were grained with 800 grit paper and because of their unusual shape; I held them in my hand while removing the excess black acrylic paint. I also grained them by hand as careful as I could; they finished with a nice satin effect due to the finer paper.
All of the Merlin parts were given 2 coats of cellulose lacquer.
Meadows and Passmore for silvering kits/wax and special lacquer.