Pianotech

  • 1.  Epoxy for Bridge Repair

    Registered Piano Technician
    Posted 17 days ago
    Hello all,

    I am doing another bass bridge crack epoxy repair later this month on an old upright. I am by no means an epoxy expert, and I am still somewhat overwhelmed by the different options from West Systems. I have actually really been enjoying working with the repair kits from Pianotek that have the pre-measured resin and hardener in the little pouches. Is there any reason not to use these for bridge repairs? For the West System experts out there, it uses 105 Epoxy Resin, 205 Fast Hardener, and 406 Adhesive Filler. I am planning on sticking in the bridge pins into the wet epoxy rather than drilling into the cured epoxy.

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    Peter Stevenson RPT
    P.S. Piano Service
    Prince George BC
    (250) 562-5358
    ps@pspianos.com
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  • 2.  RE: Epoxy for Bridge Repair

    Registered Piano Technician
    Posted 17 days ago
    Greetings, 
       The West System is basically liquid fiberglass without the fiber.  I usually use the slow cure hardener, as I think it gives me sufficient pot life without worrying about it. If you have every other pin pulled out, and inject the resin into all the open holes, you will have enough resin in there so that after pushing in the other pins and clamping, the squeeze out will be everywhere you need it to be to make the bridge a solid structure.  You will still have time to clean up the top.  I have used a handful of precut cloth strips, which after wiping off as much excess as possible, "shoe-shine" the bearing surfaces of the pins .  
       I haven't needed to , but I think the resin can be thinned with acetone or lacquer thinner if you feel you need more penetration.  Read the instructions before doing that, though. 
    Regards, 





  • 3.  RE: Epoxy for Bridge Repair

    Registered Piano Technician
    Posted 16 days ago
    Thanks, Ed. I haven't experimented with using a slower hardener - this might be a good opportunity to do that.

    Peter

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    Peter Stevenson RPT
    P.S. Piano Service
    Prince George BC
    (250) 562-5358
    ps@pspianos.com
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  • 4.  RE: Epoxy for Bridge Repair

    Registered Piano Technician
    Posted 16 days ago
    Ed,
    I haven't looked into this for some time so my information may be out of date, but...I contacted three epoxy formulators -- System Three, WEST, and MAS -- and all three advised against thinning their epoxies with anything. They all claimed it weakened the product.

    If thickness is a problem there are some epoxies that are formulated thin to begin with. The various Epo-Tek epoxies come to mind. Some of these have viscosities close to that of water.

    ddf



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    [Delwin D] Fandrich] [RPT]
    [Piano Design & Manufacturing Consultant]
    [Fandrich Piano Co., Inc.]
    [Olympia] [WA]
    [360-515-0119]
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  • 5.  RE: Epoxy for Bridge Repair

    Registered Piano Technician
    Posted 16 days ago
    Peter,

    Bear in mind that heat will thin any epoxy. The effect is temporary of course,  and it will also accelerate the curing time. However, knowing this gives you tools to manipulate the stuff creatively.

    For instance if you were to heat the entire bridge body and pins, then deposit a small amount of epoxy at the base of the pins the resin will be drawn into the void deeply and quickly. The resulting viscosity will depend on the amount of heat you direct at it or that it comes into contact with.

    Play with it to learn it's characteristics.

    Peter Grey Piano Doctor

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    Peter Grey
    Stratham NH
    (603) 686-2395
    pianodoctor57@gmail.com
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