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DonViolinClassico

Feeling a bump around the soundpost area when running my finger on the top

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I recently purchased a violin and began feeling a slight bump (not visible) when running my index finger around the sound post area. I've had this happen to me before with a couple violins in the past which I don't own anymore. Just wanted to see how common this might be and or if it's something I may need to get alarmed by?

My first thought is the sound post may be to tight.  If that is the case, and a new sound post gets fitted, would the discrete bump go away? It looks like the soundpost has been in there for decades if not longer.

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Don, your right to be alarmed.  Hard to tell much without feeling it myself, but severity depends on how sharp the bump is.  All are indications of  things wrong, but different solutions.  All deal with the soundpost being too tight.  Roll the light reflection over this area and see if you don't see a "glitch" in the light as it passes throught the soundpost area, thereby indicating a crack starting( or at least closer magnified inspection).  I recommend having this looked at asap.    Until then, loosen your strings and knock down the soundpost, if you feel competant.

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22 minutes ago, Jeff White said:

Don, your right to be alarmed.  Hard to tell much without feeling it myself, but severity depends on how sharp the bump is.  All are indications of  things wrong, but different solutions.  All deal with the soundpost being too tight.  Roll the light reflection over this area and see if you don't see a "glitch" in the light as it passes throught the soundpost area, thereby indicating a crack starting( or at least closer magnified inspection).  I recommend having this looked at asap.    Until then, loosen your strings and knock down the soundpost, if you feel competant.

I would disagree with the advice to knock down the post . If you do then the luthier you ask to look at the problem will have nothing to look at. It is possible the post is too tight but equally possible that the top is too thin in that area and would have developed a deformation regardless of the length of the post. In any case,  if the instrument is being played in any serious way then simply putting in a shorter post at this point would probably have an extremely deleterious effect on sound quality. 

My recommendation would be to get to a competent luthier as soon as possible to find out if there is a crack or not and either way the fix is likely to be some sort of patch or applied veneer on the inside of the top.

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I hope this is not the problem.  But I have seen and been informed about instruments that have just such issues due to an excess of chemical treatment of the wood prior to varnishing which softened the spruce.

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3 hours ago, David Burgess said:

It could also be a post which fits poorly, with only one edge bearing against the top, rather than entire upper surface of the post.

Good point.  That would certainly be an easier fix if that is the case.

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If it is a too long/tight post, would replacing the post with a proper one allow the wood to return to the original position, or does such a bump require something drastic?

the downward pressure of the bridge should force the wood back into place, right?

Edited by PhilipKT

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6 hours ago, nathan slobodkin said:

I would disagree with the advice to knock down the post . If you do then the luthier you ask to look at the problem will have nothing to look at. It is possible the post is too tight but equally possible that the top is too thin in that area and would have developed a deformation regardless of the length of the post. In any case,  if the instrument is being played in any serious way then simply putting in a shorter post at this point would probably have an extremely deleterious effect on sound quality. 

My recommendation would be to get to a competent luthier as soon as possible to find out if there is a crack or not and either way the fix is likely to be some sort of patch or applied veneer on the inside of the top.

I wasn't thinking about that( what Nathan said).  Bottom line, if you have access to a luthier asap, then do as Nathan says, if not, I'm worried that by the time you can get to a luthier, further damage will occur.  I'm just being a negative Nancy....and a worry wart.  For purposes of determining the problem, Nathan is correct.  I ALWAYS freak out a bit about a bump in this area.  It's usually accompanied by a starting crack that the average player can't see.

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2 hours ago, PhilipKT said:

If it is a too long/tight post, would replacing the post with a proper one allow the wood to return to the original position, or does such a bump require something drastic?

the downward pressure of the bridge should force the wood back into place, right?

More likely the whole top may sink with no effect on the localized bump.

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16 minutes ago, nathan slobodkin said:

More likely the whole top may sink with no effect on the localized bump.

I’m not sure I follow you. Are you saying that if a too-tight sound post creates an upward bump, replacing it with a correct length sound post will, rather than correct the bump, cause the entire top to sink?

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11 hours ago, PhilipKT said:

I’m not sure I follow you. Are you saying that if a too-tight sound post creates an upward bump, replacing it with a correct length sound post will, rather than correct the bump, cause the entire top to sink?

Basically yes. I the top was supported all around the post area then perhaps pressure on top of the bump might push it back down but the top isn't supported and the bridge is not actually pressing on the bump but adjacent to it.

In order to press out the bump the top must come off and be pressed into a cast over time. These kinds of very localized deformation can be pretty stubborn to correct. If there is a crack, of course, the bump would disappear in the patching process.

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1 minute ago, nathan slobodkin said:

Basically yes. I the top was supported all around the post area then perhaps pressure on top of the bump might push it back down but the top isn't supported and the bridge is not actually pressing on the bump but adjacent to it.

In order to press out the bump the top must come off and be pressed into a cast over time. These kinds of very localized deformation can be pretty stubborn to correct. If there is a crack, of course, the bump would disappear in the patching process.

Yikes. When I got my cello, after about a year, I noticed that one of the treble F Hole wings Had sunk just a little bit. I called the maker who said that he always sends his instrument out with very slightly short sound posts. When the instruments come back for adjustment he puts in a proper one.(he told me why but I don’t remember)

I went back for adjustment, he did, and everything is fine 14 years later. It seems I could be very glad he did not put in a post that was too long

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Yikes. Thanks guys this is very informative. I'm crossing my fingers to see if my luthier will accept me to drop in today. With the whole quarantine thing his doors  have been closed until the beginning of May.

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I had had success in reforming sound post bumps on double bass tops by

moving the sound post forward so it pushes up directly under the spot where the

bridge foot would normally sit and then moving the bridge back so its

right foot presses

down on the sound post bump and then tightening the strings.

It does take some time for things to even  out, like weeks or months,

but the instrument is playable in this condition while it is being

reformed,

albeit with a longer string length. Carefully warming the area with a

heat gun can help speed the process up,  just be careful,

watching the varnish for overheating.

 

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13 hours ago, PhilipKT said:

I’m not sure I follow you. Are you saying that if a too-tight sound post creates an upward bump, replacing it with a correct length sound post will, rather than correct the bump, cause the entire top to sink?

Yes,if the back is too thin its like driving a post into the mud, it just keeps sinking, and then eventually will break through or at least crack the back. If you shorten the post the top will compress down to take up the dimension change.and then drive the post into the too thin back, thus lowering the top even more.

My experience is that if the plates are of proper dimension that a post has to be really crammed in there to create a out'y dimple, most times it will just splay the arches a wee and then be prone to developing a crack, an out'y dimple does imply a too thin back imo. Maple at very thin dimensions has a rubbery quality and can conform to the post end butt 

I would think about a skid patch if its cost worthy 

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