fiddler135 - Posted - 01/08/2023:  12:58:12

Any thoughts on how to get hot glue to work itself into a center seam? I just noticed that I have an unglued place on (what will be) the outside surface of the plate right between the rear corners. The arching is nearly complete. No graduation has been done. I can force the spot open with my hands by bending the corners down. I can't get the seam to open on the opposite side or anywhere else along the joint. I suspect I got a cold joint in this one spot (because one plate rocked over during the gluing process)  but regardless of the cause I have a spot I need to work glue into some way without disassembling the joint. I don’t think the joint will break clean. If it would that would be the solution but for now we’ll assume that it won’t. The joint looks tight but opens slightly for a distance of about 2 inches, looking through a magnifying glass. I have also tried to get the joint to break (clean) by forcing the joint open over the edge of the workbench with my hands. I still just get the joint to open in the same way.

Edited by - fiddler135 on 01/08/2023 13:23:57

Brian Wood - Posted - 01/08/2023:  14:37:41

I'd be strongly inclined to saw the joint apart and start over, unless there's not enough width and height in your plate to do that - you said the arching is nearly complete. Otherwise you could still work the joint open with heat and moisture and a knife, which would probably take a long time and still result in needing to redo the joint because of any nicks etc. that might be left from the process. Without a picture it's hard for me to know what I would try. You might be able to force glue in with a syringe. Heat the joint first to soften existing glue. Clamp once you get new glue in. Remember that there's only 1/10" thick or so that will remain after finishing carving, more if it's at the blocks. Is it possible your crack will be carved away with further work? Good luck.

fiddler135 - Posted - 01/08/2023:  15:35:11

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Originally posted by Brian Wood

I'd be strongly inclined to saw the joint apart and start over, unless there's not enough width and height in your plate to do that - you said the arching is nearly complete. Otherwise you could still work the joint open with heat and moisture and a knife, which would probably take a long time and still result in needing to redo the joint because of any nicks etc. that might be left from the process. Without a picture it's hard for me to know what I would try. You might be able to force glue in with a syringe. Heat the joint first to soften existing glue. Clamp once you get new glue in. Remember that there's only 1/10" thick or so that will remain after finishing carving, more if it's at the blocks. Is it possible your crack will be carved away with further work? Good luck.

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The plate is too narrow to saw it apart and redress. I will be carving away about 1mm but I don't think that the part is glued together below there. I think that the challenge is in getting the new glue into the joint while getting the old glue to soften and bond to it.  I have a french fry warmer on order. In the meantime I will carve away the excess and see if it is glued underneath. I can also come up with a clamping method. Thanks 

The Violin Beautiful - Posted - 01/08/2023:  17:13:51

quote:

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Originally posted by fiddler135

Any thoughts on how to get hot glue to work itself into a center seam? I just noticed that I have an unglued place on (what will be) the outside surface of the plate right between the rear corners. The arching is nearly complete. No graduation has been done. I can force the spot open with my hands by bending the corners down. I can't get the seam to open on the opposite side or anywhere else along the joint. I suspect I got a cold joint in this one spot (because one plate rocked over during the gluing process)  but regardless of the cause I have a spot I need to work glue into some way without disassembling the joint. I don’t think the joint will break clean. If it would that would be the solution but for now we’ll assume that it won’t. The joint looks tight but opens slightly for a distance of about 2 inches, looking through a magnifying glass. I have also tried to get the joint to break (clean) by forcing the joint open over the edge of the workbench with my hands. I still just get the joint to open in the same way.

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If you want to keep the rest of the plate glued, you can heat the affected area with a hair dryer or heat gun from the outside. Flex the plate gently to open the seam enough to work glue into it. A good strap clamp will exert the necessary force from above to help. You can heat the seam from the inside to help the glue work its way down and bond with whatever is there already.

I've repaired open center seams on all kinds of violins. Sometimes it can be quite challenging when the opening has been there for a long time. In your case where the seam is only barely open, the process should be rather simple. A fresh glue joint that hasn't gotten dirty or stained is a big help as well.

Or

If there's an opening, you could work hot water or alcohol into the seam to open it. I wouldn't put a knife in--that will mar the gluing surface and prevent a good joint later. You can mount the plate halves on a shooting board and the go over the glue surface with a plane on the finest cut you can accomplish to assure there aren't high spots. Check with a good straightedge and rejoin the halves. Do a good dry run to be sure there aren't openings. 

Edited by - The Violin Beautiful on 01/08/2023 17:22:00

fiddler135 - Posted - 01/09/2023:  03:27:03

quote:

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Originally posted by The Violin Beautiful

quote:

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Originally posted by fiddler135

Any thoughts on how to get hot glue to work itself into a center seam? I just noticed that I have an unglued place on (what will be) the outside surface of the plate right between the rear corners. The arching is nearly complete. No graduation has been done. I can force the spot open with my hands by bending the corners down. I can't get the seam to open on the opposite side or anywhere else along the joint. I suspect I got a cold joint in this one spot (because one plate rocked over during the gluing process)  but regardless of the cause I have a spot I need to work glue into some way without disassembling the joint. I don’t think the joint will break clean. If it would that would be the solution but for now we’ll assume that it won’t. The joint looks tight but opens slightly for a distance of about 2 inches, looking through a magnifying glass. I have also tried to get the joint to break (clean) by forcing the joint open over the edge of the workbench with my hands. I still just get the joint to open in the same way.

---

If you want to keep the rest of the plate glued, you can heat the affected area with a hair dryer or heat gun from the outside. Flex the plate gently to open the seam enough to work glue into it. A good strap clamp will exert the necessary force from above to help. You can heat the seam from the inside to help the glue work its way down and bond with whatever is there already.

I've repaired open center seams on all kinds of violins. Sometimes it can be quite challenging when the opening has been there for a long time. In your case where the seam is only barely open, the process should be rather simple. A fresh glue joint that hasn't gotten dirty or stained is a big help as well.

Or

If there's an opening, you could work hot water or alcohol into the seam to open it. I wouldn't put a knife in--that will mar the gluing surface and prevent a good joint later. You can mount the plate halves on a shooting board and the go over the glue surface with a plane on the finest cut you can accomplish to assure there aren't high spots. Check with a good straightedge and rejoin the halves. Do a good dry run to be sure there aren't openings. 

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I assume then I need to graduate the plate before attempting to work glue into the joint? Then I can use a strap clamp to pull  the edges together while forcing the crack open and applying heat and glue? 

The Violin Beautiful - Posted - 01/09/2023:  06:22:37

quote:

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Originally posted by fiddler135:

I assume then I need to graduate the plate before attempting to work glue into the joint? Then I can use a strap clamp to pull  the edges together while forcing the crack open and applying heat and glue? 

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It's up to you if you want to graduate first, although I would caution that doing so might open up more of the seam as you're gouging against it.

I would prefer to stabilize the opening first. The plate might be a lot stiffer because it's not thinned out yet, but it should still be somewhat flexible so that it'll draw glue in. The strap clamp can provide the pressure over the arch needed to draw the opening together. 

fiddler135 - Posted - 01/09/2023:  09:20:27

quote:

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Originally posted by The Violin Beautiful

quote:

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Originally posted by fiddler135:

I assume then I need to graduate the plate before attempting to work glue into the joint? Then I can use a strap clamp to pull  the edges together while forcing the crack open and applying heat and glue? 

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It's up to you if you want to graduate first, although I would caution that doing so might open up more of the seam as you're gouging against it.

I would prefer to stabilize the opening first. The plate might be a lot stiffer because it's not thinned out yet, but it should still be somewhat flexible so that it'll draw glue in. The strap clamp can provide the pressure over the arch needed to draw the opening together. 

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I assume you mean I can use the strap clamp to both open and close the crack? I will soon have heat sources to use but will heat alone be enough to soften the old glue so that the new glue will bond to it? 

fiddler135 - Posted - 01/10/2023:  05:46:15

quote:

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Originally posted by fiddler135

quote:

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Originally posted by The Violin Beautiful

quote:

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Originally posted by fiddler135:

I assume then I need to graduate the plate before attempting to work glue into the joint? Then I can use a strap clamp to pull  the edges together while forcing the crack open and applying heat and glue? 

---

It's up to you if you want to graduate first, although I would caution that doing so might open up more of the seam as you're gouging against it.

I would prefer to stabilize the opening first. The plate might be a lot stiffer because it's not thinned out yet, but it should still be somewhat flexible so that it'll draw glue in. The strap clamp can provide the pressure over the arch needed to draw the opening together. 

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I assume you mean I can use the strap clamp to both open and close the crack? I will soon have heat sources to use but will heat alone be enough to soften the old glue so that the new glue will bond to it? 

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I should've asked only if adding water would be a help to soften the glue in this case. Obviously heat alone will soften glue, as anyone knows who has left a violin in a car, and hot glue will bond to the old.