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Old 10th Mar 2007, 12:48 pm   #1
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Default Ebonite cleaning / preserving

Does anyone have any advice on cleaning or polishing an ebonite panel on a 1920s radio? It has some white deposits on its surface that I would like to remove whilst retaining the shine if possible. Also any tips on preventing or reducing future deterioration of this material would be appreciated?


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Old 10th Mar 2007, 8:05 pm   #2
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Default Re: Ebonite cleaning / preserving

Many years ago, I was successful in polishing an ebonite panel from a 1920s radio using Brasso followed by Perspex polish in successively finer grades. This eventually restored the panel from a treacly brown to a shining black but I do not know how long the sheen lasted.

I seem to remember an article in a BVWS Bulletin by Fons van den Berghen on how he restored either some of his telegraph instruments or an early Marconi receiver, but either he did not give details of the ebonite restoration, or I could not find the article. The photographs certainly showed a beautifully restored panel.

Depending on the importance of the panel, I would not be too hesitant about trying to polish it as I have suggested, but keeping is polished is another matter.

This is the kind of question I would once have asked the staff of one of the big museums but they seem to be too short-staffed to reply now. There is also the controversial question as to whether items should be restored or merely conserved, with most institutions favouring simply conservation, although I suspect this is sometimes making virtue of necessity as there is neither the money or people available for good restoration.

The merits of restoration versus conservation of paintings seems to be entirely different for some reason.

Peter M. Munro

Last edited by Darren-UK; 13th Sep 2007 at 12:53 pm. Reason: Ref to another, now defunct, thread removed.
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Old 11th Mar 2007, 4:35 pm   #3
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Default Re: Ebonite cleaning / preserving

These people do an ebonite black polish and it would appear to be a type of, or similar to, french polish. Whether this is actually for use on ebonite or just gives 'that look' is unclear however.
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Old 11th Mar 2007, 4:37 pm   #4
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Default Re: Ebonite cleaning / preserving

I advise using T cut paint restorer which has more bite than brasso on plastics , but need to experiment first on an unseen part .As regards to restoration , things like reviving ebonite is much preferable to leaving it drab and dirty as it isnt altering anything , like repolishing cabinets for the sake of a few scratches or changing componants . some items look terrible in as found condition, it all depends on what the item is what the work needed is rarety etc i suppose.
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Old 11th Mar 2007, 9:44 pm   #5
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Default Re: Ebonite cleaning / preserving

As Peter mentioned above I tried using Brasso to try and restore some ebonite parts I had on hand that had turned a shade of olive green, and unfortunately it seems to have not affected the colour (although much more shiny).

Has anyone tried using fabric dye to dye ebonite like you can do with plastics? Also, on some vintage pen websites some people talk about a much-kept-secret formula that chemically restores "hard rubber", does anybody know anything about that?

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Old 16th Mar 2007, 6:35 pm   #6
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Default Re: Ebonite cleaning / preserving

Thanks everyone for your responses.

Before posting my question I spent some time attempting to find some definitive advice on the internet. I did find some articles on preserving various plastics published by museums, but no real guidance on what to do with ebonite.

I was concerned about using water or a solvent to try and clean the panel without knowing what chemical reactions might take place, etc. The following is a statement from one conservation scientist that I found:

"Hard vulcanized rubbers like ebonite and vulcanite contain 30% or more sulfur vulcanizing agent. Oxidation in air of sulfur compounds in the rubber produces sulfur oxides which react with atmospheric moisture to eventually form sulfuric acid. Sulfuric acid may be present as droplets on the surface of the hard rubber. It can react with ammonia in the atmosphere to form ammonium hydrogen sulfate and ammonium sulfate."

As suggested I might try polishing the panel to improve its appearance. I have some Greygate Plastic Polish. I think this is a similar product to the perspex polish that you mentioned using, Peter?


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Old 25th Mar 2007, 8:50 am   #7
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Default Re: Ebonite cleaning / preserving

I find the brasso method works well.
I finish off with a drop of linseed oil on a rag to bring back the shine & colour.
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Old 25th Mar 2007, 6:35 pm   #8
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Default Re: Ebonite cleaning / preserving

The whitish staining you get on plastics over time (and on old car paintwork etc) is known as the "bloom". It's genrally the result of an imperfect balance in the constituent ingrediants in the plastic, and one or more of them make their way to the surface over time. It's quite safe to polish the surface again with a mild abrasive (Xebo, Barkeeper's friend, Brasso, T-cut etc), provided the ebonite isn't acting as an insulator or anything.
(My Grandfather was a rubber and plastics research physicist, he's been lecturing me...)
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