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What's that yellow stuff around transformers?

  1. Oct 3, 2014 #1
    I need to find something that I can wrap around the coil of a bottle radio (image below) to keep the magnet wire from unwinding. Lacquer is messy and time-consuming. I'm hoping there is a translucent tape that I can use? Someone suggested using Kapton tape, but it's very expensive and a bit overkill for my application. Maybe I can find a generic roll on ebay. I'm going to be showing how to make crystal receivers to kids (ages 7-11). I'd rather not use lacquer (fumes and drying time). Suggestions?

    bottle radio.jpg
  2. jcsd
  3. Oct 3, 2014 #2


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    The yellow stuff is a plastic film insulation that separates the outer windings from the immediate environment.
    PVC tape or clear sticky tape would work OK as the voltages involved are very low.
  4. Oct 4, 2014 #3
    I think the special characteristic of that yellow tape is that it can handle high temperatures.
    Since your device won't get hot or handle high voltage , I think you could use anything you've got at hand, mums hair spray, spray paint , cling-film, hot glue, any glue ,sellotape ....
  5. Oct 5, 2014 #4
    The yellow stuff is commonly called Mylar tape, Mylar being a trade name owned by Dupont. It is a polyester tape with good electrical properties and low cost.
    Transformers are also dipped in a bucket of varnish and a vacuum is drawn on the transformers and varnish causing the varnish to penetrate into crevices.
    Afterwards, the transformers are restored to atmospheric pressure and placed into an oven where the varnish bakes into a hard substance that protects the transformer and discourages any vibration.

    I suspect there's a number of varnishes that are solvent based (just allow the solvent to dry away) Perhaps some guys on the Tesla Ring will have a suggestion.

    - Mike
  6. Oct 5, 2014 #5

    jim hardy

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    I have used woodworker's polyurethane varnish on electric motor windings.
    Also engine enamel in spray cans from the auto parts store. The engine enamel dries quicker but the colors tend to be garish,,,
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