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Thread: Please talk to me about sinkage

  1. #1

    Default Please talk to me about sinkage

    Hi everyone,

    I'm interested in a 1920s mandolin that is described on the seller's website as having a touch of sink.

    The short question is: should this be a dealbreaker?

    More generally, what exactly is sinkage? My guess is that it is a warping of the wood from its original shape. I assume this is irreparable, but will it necessarily get worse over time? Also assuming that it will distort the sound.

    Will I be able to know sinkage will I see it - is it easy to spot, and what do you look for?

    * Note: I looked at archived threads, but they seemed more focused on fixing an existing problem. I'm more interested in knowing whether I should I just stay away from this mando. Or maybe all mandos this old have some degree of sinkage.

    Thanks in advance for sharing your thoughts.
    Last edited by Penguin41; May-03-2022 at 8:31am.

  2. #2
    harvester of clams Bill McCall's Avatar
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    Default Re: Please talk to me about sinkage

    Depends on how much you pay for it and the cost of the repair.

    Many instruments have had sinkage remediated and have played wonderfully for years.
    Not all the clams are at the beach

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  3. #3
    Registered User urobouros's Avatar
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    Default Re: Please talk to me about sinkage

    Though I'm far from an expert, I think sinkage results from the bracing beginning to fail. It's often repairable or, at least, treatable so as not to worsen. I'm a sucker for vintage myself and, if you can avoid the deep & expensive rabbit holes, the tone & feel can give you chills. Or it could all be in my head Either way, I hope it's a winner!
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  4. #4

    Default Re: Please talk to me about sinkage

    I have a 1916 F4 and noticed a minimal amount of sinkage compared to unstrung. It played fine. Nevertheless I decided to try D and Gs strings slightly lighter and put on 25 and 38 instead of 26 and 40. I would say it now seems to have virtually no sinkage to the eye and in fact plays better. It is as loud as you would need. I honestly do think it is better all round. Hope this helps. Remember if it hasn't collapsed after 100 years I doubt it will now.

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  6. #5
    Registered User
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    Default Re: Please talk to me about sinkage

    Quote Originally Posted by Penguin41 View Post
    a 1920s mandolin [with] touch of sink
    I have shared my story here before. Went to buy my first "real" mandolin
    to Mandolin Brothers on Staten Island (about 3 hour drive up the Sunrise Hwy,
    across Brooklyn and Verrazzano bridge), played every mandolin in the joint,
    best sounding and best playing were a new bruce weber f-style and
    a 1918 gibson A4 with a sink hole in the top. stan jay gave me a good discount
    for the sink hole and told me not to worry about it.

    and right he was. sink hole was stable for 15 years, until one day... so into repairs it went and
    problems surfaced: glue join on the "one gibson brace" failed, failed because it was incorrectly
    repaired in the past (was not clamped) and top wood is too thin. bottom line, it is now x-braced,
    can take medium-to-heavy strings, is louder than before, works great at bluegrass jams
    and irish sessions. (I play a bruce weber octave at most gigs).

    what I think about all this now?

    if you want an old gibson, go for it, they are great. but if it has not yet been "fully restored" (not
    repaired, but "the works" restoration - internal braces, frets, neck, etc), expect to be the lucky
    caretaker to pay for the privilege. this means you need to budget for it (for me, it was like buying it again) and know somebody who can do the work. I think this is the main reason old gibsons
    are currently depressed in value.

  7. #6
    Registered User sunburst's Avatar
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    Default Re: Please talk to me about sinkage

    Quote Originally Posted by Penguin41 View Post
    The short question is: should this be a dealbreaker?
    It depends on how bad it is, and what the cause is.

    Quote Originally Posted by Penguin41 View Post
    More generally, what exactly is sinkage?
    Top sinkage can be caused by faulty bracing, brace glue joint failure, top wood not stiff enough, top wood too thin, poor treatment of the instrument; especially overheating and so forth.

    Quote Originally Posted by Penguin41 View Post
    Will I be able to know sinkage will I see it - is it easy to spot, and what do you look for?
    It depends on how bad the condition is and your experience with similar mandolins and what they normally look like. If it is severe you will probably see it. If it is minimal you might not. What you look for is a difference in arch shape from a normal arch shape, and if you are not familiar with a normal arch shape it is hard to see if it is different.

    Without seeing the instrument in hand and knowing your standards of acceptability it is impossible for even the experienced among us to know if you should buy it or pass.

  8. #7
    Teacher, repair person
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    Default Re: Please talk to me about sinkage

    John has hit the mark on this.

    Lots of old instruments [and some new ones] develop some top distortion. Sometimes it is because a glue joint has failed, sometimes it is because a brace has cracked, sometimes it is because a top is weak, or because an instrument has been overheated or over-strung.

    And we cannot diagnose the cause of the distortion or accurately assess the remedy for the problem from pictures.

    --------------------------------------------------------------------------------------------------------------------------------

    My first mandolin was a Korean instrument that I bought new in 1979. The top caved in two years later. By that time, I had found a better instrument and given the Korean job to a friend, and I'm not sure of the exact cause of the top failure. I suspect that it was either underbuilt, or a glue joint turned loose.

    --------------------------------------------------------------------------------------------------------------------------------

    I acquired a Gibson mandola in 1983. It had a cracked tail block and a loose brace. Back then, I was pretty new to repair work. I didn't know much about what I was doing, and it was the only mandola I had ever seen or played. When I opened the mandola to repair the tail block, I sought advice from repairman Tom Morgan. He advised me to replace the transverse brace with tone bars, provided the wood, arched the pieces to fit, and marked their location on the top. I glued in the tone bars myself and graduated them by instinct, with no real knowledge of how much wood to carve away. In short, I guessed. I re-assembled the instrument, and strung it with an off-the-shelf "standard" set of D'Addario mandola strings. Although they seemed a bit stiff, I assumed that D'Addario had engineered their sets correctly. They were either EJ72: 14-23-34-49, or EJ76: 15-25-35-52.

    Later in the 1980's, I noticed some minor top sinkage. Around that time, I met Norman Blake and showed him the instrument. He gave it one strum, told me the strings were too heavy for it, and recommended that I buy single strings and lighten the load. I eventually settled on 12-20-32-50. It has been strung that way ever since. The degree of distortion decreased, but never went away completely. Since then, the mandola has been used on several recording projects. When I store the instrument for a long time, I de-tune it a step or two low, and it has remained stable for 30 years.

    With what I know now, the cause of the distortion could have been one of three things. It could have been caused by the too heavy off-the-shelf strings, or perhaps I worked the tone bars down a little too far, or when Tom laid out the tone bars, he only extended them to the bottom of the sound hole, and I now believe it would have been better to run them up to the upper end of the soundhole. If the instrument ever shows signs of deterioration, I'll open it again and re-do the tone bars, but so far there hasn't been any need to worry about it. The instrument sounds and plays well, and it may very well hold together much longer than I will.
    Last edited by rcc56; May-08-2022 at 3:44am.

  9. #8

    Default Re: Please talk to me about sinkage

    From my very limited observations, I think sinkage is easiest to gauge by looking at the sound hole or the f holes on respective instruments rather than trying to evaluate broader areas. On my old bowlbacks, the inlay surrounding the sound hole will start to unseat with very tiny deformation in that area. This can also be caused by the neck starting to rise, which is different than under-bridge sinkage, but either way tells you there’s a problem.
    On f hole instruments, unless I’m mistaken, both sides of the cutout should remain in the same plane, as if they are cut out of a top that’s already in its final shape. It’s easy to see if one side is dropping. Of course, there are other ways to make the holes, so doesn’t apply to everything.

    Another possibly relevant note is that the entire downforce on a top by the bridge is the result of not only string tension, but the breakover angle. At very low angles, seen on old instruments, with non-adjustable geometry, the force is low. Sometimes so low that a little bar behind the bridge screwed to the top is necessary to add a little. On an archtop, it can’t be very low, and supposedly is related to desirable sonics. But picture an instrument where a bridge is cranked upwards to address a different issue, that downforce is going to increase. A neck reset with too much angle, resulting in a too-high bridge could be the fabled straw on our wooden camel’s back.

  10. #9

    Default Re: Please talk to me about sinkage

    I look at it like this, the instrument hasn't failed after 100 years -- it has succeeded in lasting that long! Now maintenance is required to make it last another 100 years, IMHO.

    I would figure in the repairs as part of the total investment.

    Good luck!

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