How to Clean Dirty Dial Glasses of Earlier Radios

  One of the serious problems of old radio restoration is the cleaning of dirty dial glasses. Those belonging to the radios made in the 60's and later are printed with durable paint and they can easily be cleaned with a lightly moist soft cloth. Some of them can even be safely washed under running water. However, those installed in radios of the 50's and before have fragile printings. They must be cleaned with utmost care in order not to "clean everything".

The dial glasses of the earlier radios need special attention for cleaning for several reasons. First, the printings used on these dial glasses, either from the paint materials or from the printing technique used or both, are of an easily erasable quality. They have also endured the damaging influences of time longer. They have been exposed to weather elements (the sun, humidity, cold, etc) that have made the printings on them even more fragile. Finally, time has accumulated more dirt and filth on them compared to dial glasses of more recent radios.

Then, what must we do to clean those dial glasses with highly erasable printings?

When I first started my radio collection hobby, I did not now anything about the peculiarities of the dial glasses. I wiped a few of them "totally" clean with a wet piece of cloth. Although I later tried different degrees of wetness of the cloth to see if I would be successful in removing the dirt without removing the printings, the result was not always 100% as expected. Finally, one day a fellow hobbyist explained to me that the best way of cleaning a dial glass was through breathing upon the glass at approximately 5 cm distance and immediately wiping the breathed-upon area gently with a patch of cotton. Breathing (upon the side of the glass with the printing) must be applied on a different area at a time and wiping should not be too strong. After going over the glass once, it may not look clean enough. Do not worry; you can repeat the cleaning process until the glass looks clean enough. However, do not focus yourself and breath repeatedly on a certain area, since this would weaken the printing. I would recommend that you wait a few hours or a day between the passes so that the humidity from your breathing will not dissolve the printing.

I have been quite successful with this method. However, no method is 100% assured. Based on the condition of the glass, the use of controlled breathing and gentle wiping and allowing enough time between repeats are important. In other words, loving attention and patience are critical factors in cleaning a dirty dial glass without damaging it.

Suleyman Acar

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Yes, this is surely a big problem if you washed away the dial printing. I too have a bitter experience of that. But there is another problem with dial glasses which have been broken and especially those with golden printing, since you can’t get the gold to look like gold if you try to get a picture of it with a camera. Second, it’s almost impossible the reproduce the picture on a new glass or plexi glass in the ordinary way. The photo dealer told me that it must be printed with some kind of silk printing (whatever that is) and the costs are huge.
It’s easy to shoot a picture of the assembled broken glass and heal it afterwards with a photo application like PhotoShop, but as mentioned to get it properly on glass is easier said than done.

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This is my first post so I hope I am doing it in the right way.

I would like to add that it is a good practice to always take a high resolution picture of the dial glass before attempting any cleaning/restoration. That way if something goes wrong, you at least have the picture to come back to.

In many radios I have restored, the dial lettering was crumbling and falling appart and it was not possible to save it. An example are the argentine "Douglas" radios of the late 40's where even the slightest rub is enough to remove the lettering. So what I did was to take a digital picture of the dial and "touch it up" using any photo software. Then I printed the dial on a color laser printer using transparency film and attached this to the back of the original glass. To hold it in place you can use 3M spray adhesive or you can "sandwich" the transparency film between the glass and a piece of plexiglass. If done with care, this method withstands close inspection.

Gold and silver are a problem since these colors do not get printed on a conventional color printer.

Mario

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