Porcelain dials

[eezy]

Am I right in thinking that if there is a hairline crack, the watchface would be porcelain?

Also if an old watch face is faded would it be more likely to be enamel?

I have a family heirloom trench watch that I would like to explore one day to find any maker's marks but I think it may be a porcelain dial and I would hate to damage it if it's a bit tight coming off.

[TimFitz]

Can you post some photos?

[eezy]

First time pic so hope you can see it.

[Tudor]

That's a really cool piece.

First: full disclosure- I've never restored a porcelain dial.

But, I had heard a rumor (or reads somewhere) that porcelain dials with cracks can be cleaned up in ultrasonic to remove the dirt from the crack and that alone makes then 99% invisible. I believe simple water was/is the solvent.

Further, I seem to recall a restoration powder of some sort that is used after cleaning to fill in larger cracks.

But either way, the cracks must be clean before you try to "repair" them, however that may be done.

Maybe old hippy has some pointers as he's been at this stuff for a lot longer than I have! Maybe even has some more useful first-hand experience to draw upon.

[TimFitz]

You are correct, I use polident denture fizzy tablets which works well. I have also used an ultrasonic cleaner with a cleaner I mix up. You will never get the hairline cracks completely but you can get them to be way less noticeable.   

[Tudor]

Cool!

 

Based on the photo posted above, a good cleaning should be all that is needed. I am not able to discern the cracks in the photo as it is...

[eezy]

Thanks for the advice guys. I'm surprised at the ultrasonic, I would have thought the vibration would have opened up the crack.

On this one the crack is not visible with the naked eye but under magnification there is a slightly darker line running from 8 minutes past to the centre hole.

So am I right in thinking this is a porcelain dial?

[TimFitz]

The ultrasonic has never made the hairline cracks larger. I would never try it on dials with larger than hairline cracks.

Here is a dial that I ran through both ultrasonic & polident soak. I cant find the before photo. so you will have to take my word.

[Michael]

I would say with almost certainty that it is an enamel dial, which means it will have a metal backing to which the enamel is baked onto. I would be amazed if it was porcelain, which does not have the metal backing (image a porcelain plate or vase - no metal backing - solid ceramic like substance) .

[eezy]

1 hour ago, Michael said:

I would say with almost certainty that it is an enamel dial, which means it will have a metal backing to which the enamel is baked onto. I would be amazed if it was porcelain, which does not have the metal backing (image a porcelain plate or vase - no metal backing - solid ceramic like substance) .

Thank you Michael, that clarifies it somewhat. I do believe when I took the movement out last time, the dial has a metal backing.

Thanks to all for the info.

[JohnR725]

6 hours ago, eezyrider said:

Thank you Michael, that clarifies it somewhat. I do believe when I took the movement out last time, the dial has a metal backing.

 

8 hours ago, Michael said:

I would say with almost certainty that it is an enamel dial, which means it will have a metal backing to which the enamel is baked onto.

I thought I would clarify this you're not going to see the metal on the backside of a enameled dial.  When enamel is baked on the metal it has a problem of having a different thermal expansion than the metal itself. This means that when it cools after being fired the enamel has a tendency to crack. To prevent that enamel is put on the backside of the dial to cancel out the different thermal expansion on the front side. For example this is a Hamilton pocket watch dial front and back. notice typical of American pocket watch dials the subsecond is recessed and is actually a separate  enameled dial soldered the main dial.

 

[dieale2]

Pretty impressive that these hundred year old dials survive an ultrasonic bath. Brushing a modern dial can make me nervous!

Although I am still not 100% on ultrasonic. I feel like it could open up new cracks from all the vibration. Clearly people use it to great success but I learnt that it's good to be paranoid about damage in watchmaking.

From the old books I read, they suggest just using soap and water with some gentle scrubbing. If it was me, I'll do that.

[transporter]

I use the false teeth cleaning tablets, glass of cold water drop in the tablet then the dial and let it bubble away, dirst is removed from the crack and it’s gone! I was told to be careful about the numerals incase they didn’t have a laquer over them as they could be lifted off , I haven’t experienced this yet and have done qu a few