Just noticed on a Hamilton Railway Special dial that it has a large hairline from center out to the 9. It is in a cabinet and was not like that when it was put there several months ago. What could have caused this? Humidity, temperature, age, thunder, etc.??? Anyway to avoid this? Thanks

Porcelain as well as enamel painted and melamine dials will become stressed over time and develop these cracks. Remembering that they are held in place at 3-4 different points and generally as each foot screw is tightened, we exert downward pressure to make sure it is flush with the top of the plate, when we are finished tightening it down we have stressed the thin finish "into" a position that is not relaxed.

NOTE; Melamine dials cleaned with any cleaner may develop cracks after cleaned and put away only to be discovered later. It is a chemical reaction to the plastic and the cleaner. Early on [40 years ago] I had a NOS RWS Hamilton melamine dial that was dusty. I wiped it down gently with an alcohol based cleaner and it looked great. I put the bezel back on and went to bed. Next morning with the alcohol vapors trapped by the in place bezel, there must have been 500 spiderweb cracks in the dial Lesson learned.

Then too, I seem to notice a new crack in my face each time I look in the mirror

Since no porcelain dials have been made in around 60 years and no melamine dials in about 40 years, we can expect hairlined dials to be the normal in what's available and what we might have stored away.

Fine porcelain china seems to suffer from the same delima even stored away for years in a china cabinet and unused.

regards,
bb

IMO the biggest cause of hairlines, especially emanating from the area of the feet are a direct result of over-tightening the dial screws. I can't believe how tight some of these things are when I tear down a movement. They just have to be snug. The screw is going into soft material and needs no more than a very light touch. Stressing the metal feet transfers that stress to the metal part of the dial and in turn the porcelain.

I'm sure as Buster says that a lot of them are inevitable, but please go easy on those dial screws!

Thanks Buster and Roger for the informative information. Bob

I would think temperature would be a big culprit along with age. You have one material (Porc) bonded to another material (metal) that have different rates of thermal expansion and even though the temperature changes may be small the contractions and expansion cycles over time can trigger a hairline if there is a slight defect and around the edges and in the hole areas would be the biggest chance for one to develop.

As Roger mentioned, I am not sure who cranks some of these hold down screws on, since sometimes I think I purchased a watch that had the dial put on by King Kong.

Not sure about the enamel but I know the melamine dials will crack easy with temperature change I remember sending a perfect NOS melamine dial out last winter and when the buyer unwrapped it there were a couple craze cracks in it. I figured it being winter the cold got to it.

Rob-

You are correct on the cold making hairlines show up on the melamine dials. I have not had this issue personally, but am aware of a lot of people having it happen. I acutally have waited to sell melamine dial hammies until warmer weather for that reason. North Dakota can easily have double digit below zero temps in the winter time here and would cause havic very quickly.

Jared

Good points on the temperature factor. When you think about how these were worn, in vest pockets close to the body, they were normally pretty warm. Claude's suggestion of number of thermal cycles with different materials bonded to each other makes a lot of sense. I guess another reason would be impact. If the case got knocked into something, that would also transfer unwanted energy to the dial and depending on its weakest areas a hairline could develop.