What Turns Acrylic Crystals Green?
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Thread: What Turns Acrylic Crystals Green?

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  1. #1
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    What Turns Acrylic Crystals Green?

    Ever bought an old watch with a slightly green plastic crystal? Here's the thread where we can find out what causes it...and if or how it can be restored to its original clarity. See pics below!
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  2. #2
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    Re: What Turns Acrylic Crystals Green?

    Isn't Gruen the German word for green?

  3. #3
    Vintage & NAWCC Forum moderator Ben_hutcherson's Avatar
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    Re: What Turns Acrylic Crystals Green?

    The first one you show looks to me like green glass...this was popular at one time. Usually the old plastic crystals turn cloudy in addition to the color change, as your second one has.

    As for what causes it, I don't have any evidence(nor have I done any investigation on it) but I suspect that they're cellulose acetate, and the yellowing is the result of the natural decomposition that happens with this type of plastic. This particular decomposition also releases acetic acid, which could cause the characteristic rusting and other damage often seen with these type of crystals.

    I have plenty of these old crystals, and access to the tools to find out what they're made of...I just need the time!
    Telfer likes this.
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    Serious collector of American pocket watches-Waltham(and the predecessor companies) is my specialty.

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    Re: What Turns Acrylic Crystals Green?

    Quote Originally Posted by Ben_hutcherson View Post
    The first one you show looks to me like green glass...this was popular at one time. Usually the old plastic crystals turn cloudy in addition to the color change, as your second one has.

    As for what causes it, I don't have any evidence(nor have I done any investigation on it) but I suspect that they're cellulose acetate, and the yellowing is the result of the natural decomposition that happens with this type of plastic.
    Is there any kind of chemical bath that can restore the plastic to its original clarity?

    Strangely, a google search turns up little on the subject of green crystals.

  6. #5
    Vint. Forum Co-Moderator Mirius's Avatar
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    Re: What Turns Acrylic Crystals Green?

    As stated by Ben coloured crystals (green, red, blue etc) were popular at one point, so there is no turning them back to clear, as they never were in the first place. I'm not sure why you want to restore a yellowed crystal as generally by the time they do this they are in poor condition anyway.
    Telfer likes this.


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