Jump to content
Maestronet Forums

Problems Gluing CenterJoint


Taylor Sincich
 Share

Recommended Posts

Hello, 

My name is Taylor and I’m new to Maestronet. Though I’ve been reading through the pegbox religiously while I am currently building my first violin I have never posted before and just wanted to start by saying thanks to all of you in this community for being such a wonderful resource in so many ways. I hope to be able to add in positive ways in the future. 

My current problem is gluing the spruce center joint. I’m aware this should be a relatively simple and basic task compared to everything else but I think it comes down to I simply have no experience with Hot Hide Glue and am unsure what I’m looking for. (It also seems to be relatively hard to explain the nuances of HHG in words) 

After two weeks and a sore wrist figuring out how to plane the joints, gluing, cutting open and re gluing the back plate 5 times I am finally happy with it. (3 times after clamping I had a visible gap along the top, once where a blade could just fit through) After all the time I spent dialing how to sharpen, set and use my plane with the maple I was surprised to get a perfect, light proof, clean,  single shaving joint in the spruce in under 10 minutes via shooting board. I understand a lot of people suggest a micro gap joint or sprung joint in the center but I felt most comfortable with the perfectly straight joint working from the C&J Art of... book.

I glued it up immediately after planing using a 1:3 mix (glue:water ratio by weight using digital scale) of Bjorne 315 bloom HHG at 140 deg. (Mixed the dry glue and cold water and let soak overnight the day before) First I gently warmed both pieces over a heater for a while then warmed the joint face with a hair dryer until slightly warm on my ear, then I poured the glue straight onto the joint from the bottle like David Sora does in his video (I think he uses a 1:4 mix but I’m not sure if that means volume, weight, etc) and rubbed together till I felt it bite, adjusted the bottom plane and let sit for a couple hours before moving and letting dry for 24+ hours. Maybe 8 seconds total working time from glue jar to untouched rubbed joint.

513A4536-A258-436C-9CA4-C48811B8AE86.thumb.jpeg.40c7aac35b45f03f19625a1e747de5dd.jpeg

D9C7D0FA-DC82-444A-8163-15E3842B73D4.thumb.jpeg.c4abf34ecddea20b20d836f6cd148a32.jpeg

To me the glue line looked (nearly) seamless after it dried except the top and bottom inch where there was a slightly visible glue line on the top of the plate but no gap (and no gaps anywhere before gluing) However when I first made cut offs from the board ends, they almost all broke near cleanly apart at the glue line. In the photo below, group 1 was the first cutoffs that made me worried. I thought maybe the ends were just not perfect so I kept trying while I had spare wood and finally got the two pieces in group 2 that had some splits along the wood and not just the glue line which led me to believe I was ok. However, after sawing out the outline, both the top and bottom cutoffs in group 3 snapped apart at the glue line after applying slight pressure with my fingers. 

5C7E75B4-2328-47F7-BCBA-2A64BDC91D44.thumb.jpeg.71cf39d53f0053d0bb0d2b9fac633554.jpeg

I guess my question boils down to this: Does this seem normal/bad/weird/good/anything to anyone? My biggest concern is having the plate split apart at the seam once’s it’s thinned out or worse after it’s carved. The idea of tightening the strings when the cutoffs popped apart as easily as they did terrifies me. Any suggestions?

After cutting apart and regluing the back plate 5 times (with 4mm of wood on the lower bouts to spare at the end!) I am confident I have more than enough extra wood to cut the seam apart and re glue the wedges before continuing if the break tests suggest that. It seems most people would cut apart and re glue if there is a clean break at the joint. I’m just not sure what I can do differently from last time. It seems like all my practice pieces are good, using almost any method, but anytime I actually glue the plates together it doesn’t work. I’ve thought time could be the issue which is why I went for only a rub joint on the top plate? For the maple joint I brushed thick glue and rubbed it in, whipped off excess, hair dryer then brushed glue, rubbed and clamped. I see some people glue size the joints before but I’m more worried about the spruce joint swelling or having too much glue than starving the joint.

B9B4A9F6-47E9-4516-A95F-6383575FAEE5.thumb.jpeg.b24e86876738829e89c272bc74810562.jpeg

673A1A82-3A80-42F5-8714-AB4B0EB54EC7.thumb.jpeg.76c8b856bc963200222d6af0d5697660.jpeg

Before doing all of this, since I had no experience with HHG, I tested glue ratios of 1:2, 1:3, 1:4, 1:5 both by weight and volume, glued up at least 50 test pieces each varying by either a rub joint, clamped joint, pouring the glue on one face and rubbing or brushing a thinner coat to both joints, then rubbing. I found the 1:2 to be the “strongest” but also had a visible glue line, the 1:3 was the “strongest” with an invisible joint, and sometimes the rub joint was just as strong as the clamped, but more often the clamped joints were a little better. Only the 1:4 and 1:5 ratios split apart cleanly at the glue line hence why I didn’t use them.

My shop does get very cold but after stoking the fire and running the heater it is always at least 65-70 deg F when I am gluing, with a heater underneath the glue area and a hair dryer to warm the wood just before gluing. I plane the joints while it’s hot in the room and glue up minutes after I have a perfect joint.

Last night I took the spruce cutoffs from the outline and planed them and redid glue tests with 1:2, 1:3 and 1:4 ratios with both rubbed and clamped joints. All but the 1:4 ratio pieces either broke away from the seam or barely on what glue line in a good way. 

4E2276D7-C98D-40C3-954F-174CDEF46BAF.thumb.jpeg.7d709021d99a06d0c3504fc847177e6d.jpeg

A63B15B2-7DD5-4496-BCED-3E2608C1ED8B.thumb.jpeg.ba8d89c0d6172e4ad1cf5d5fc52339a0.jpeg

Any advice or suggestions would be greatly appreciated! For now I am happy with the back and will continue on that while I wait to see if there are any replies. Thanks again for your time and any help offered. 

28B11101-D516-4E91-B59D-841C9372AAF5.thumb.jpeg.51023cb3d388a1ae4ae6221d9022d970.jpeg

22815C80-F0E8-47EB-B456-A5EC54692E46.thumb.jpeg.8de85a05723b14dd14316b050739109d.jpeg

Initial maple cutoffs and breaks:

05844364-043B-4146-BB67-08EB3A645BE6.thumb.jpeg.9b957827a662f301851fc9858d4336a1.jpeg

Outline Cut Off:

A2A0F180-4634-411B-863C-38B7E177DFFE.thumb.jpeg.3e75670db7543c58dbcd6d96d7562b0a.jpeg

 

 

 

Link to comment
Share on other sites

Always worry about starving the joint.  Squeeze out is easy to clean.  Some of my early projects broke apart when carving out the backsides of the plates... From too little glue to get a good joint.

I always clamp my joints using bar clamps.  I know some just rely on rubbing the joint but I would not advise this approach.

Link to comment
Share on other sites

Thanks Wood Butcher! I've read through that post, very informative. 

Shunyata, sorry, I AM worried about starving the joint, hence I usually lean toward using too much glue which I'm worried may be the issue. I always rub out all the excess and tape paper to the sides. So I should have said, I am not worried about starving the joint because I always have plenty of squeeze out. I am thinking I should re glue with clamps as well. 

Link to comment
Share on other sites

A couple of observations I'd make are that the spruce looks like it might be a soft variety of low density with not well defined growth rings. If that is the case it might soak up glue more readily and also snap more easily. The question is whether the glue was too thin or the wood failed or it was a combination of both.

Personally I would advise against using low density spruce. However European spruce which might have strong thick growth rings can present its own minor problems as far as planing a flat edge is concerned.

 

 

Link to comment
Share on other sites

30 minutes ago, Dennis J said:

A couple of observations I'd make are that the spruce looks like it might be a soft variety of low density with not well defined growth rings. If that is the case it might soak up glue more readily and also snap more easily. The question is whether the glue was too thin or the wood failed or it was a combination of both.

Personally I would advise against using low density spruce. However European spruce which might have strong thick growth rings can present its own minor problems as far as planing a flat edge is concerned.

 

 

Thanks for your reply Dennis! What do you consider soft/low density spruce? (I have no clue so I am genuinely curious) I bought all the tonewood from Rauch Tonewood. I’m very happy with it and Thomas and Johanna were amazingly helpful. 

AF0A62D2-B377-4F2F-9604-A3325DE529C1.jpeg.c798ee01610ba948e708bcdb7d13dfa9.jpegBB4D2C0F-E07C-4950-9BF2-73ABF885D01C.thumb.jpeg.bcae9d5af26e3aeebb2fdc4ae9a73d24.jpeg

Ive seen this graph somewhere else on maestronet but I’m not sure if it refers to the maple or spruce wood

DE18F5EB-3995-4837-A43A-000F686D17DD.jpeg.ea7094ebd137d35ef68ddff97c97036f.jpeg

Link to comment
Share on other sites

I suspect a bad batch of glue. I use the Bjorne glue and never had problems. Time to get some glue from a violinmaker near you.. I must compliment you. You seem to be doing everything right. And very methodically. You need a Zoom session with one of the professionals or experienced amateurs on here. Please, someone. Help Taylor out.

Link to comment
Share on other sites

Just a couple of thoughts from one who has had similar failures in the past:  1)  The Bjorn site looks like they are open to questions about their product, so I would call them.  If you do, let us know what they say.   2) Are you heating your glue in a glue pot up to the desired temp?  I understand you should avoid overheating.  3) If you do use clamps, make sure you balance the pressure (see previous threads) and don't clamp TOO tight.  

Link to comment
Share on other sites

Thanks everyone for your replies! I appreciate the feedback. 

I’m open to the possibility of bad glue but for now I assume it’s user error. Also because I have not had any issue with the glue for any other part of the build like the rib garland, the back joint seems strong and all the test pieces have been strong as well.

6454525B-7E91-4445-A52A-1F05B91D83BD.thumb.jpeg.387252391641bbb50367f37dcbf0a4b9.jpeg

I guess this photo represents my entire inquiry. Is the top glue joint bad/good/ok/not acceptable when compared to the lower? The top two pieces are the outline cut out that snapped relatively easy clean at the glue joint with 1:3 glue and a rub joint, no clamps, using the methods described above. The lower two pieces used the exact same glue (a week old at this point) and same rub joint and split away from the glue line. From what I seem to read, the clean split of the top two pieces suggests an inferior glue joint while the lower two suggest a strong glue joint. Or am I incorrect in assuming this? I know the boards are definitely glued together and very strong but does the clean break suggest when I thin out the plate it will pop apart as easily? (Not that anyone could definitively tell me without having been here) I understand there are 100 reasons the plate joint went bad, bad glue ratio, overheated, too thick, too thin, not a perfect joint, etc. and those are my faults, probably not the glue itself.

 

26E067C8-A522-4433-B294-61E1A494C4F6.jpeg.3c03675f30e56be234f6fb4195634a40.jpeg

To shed a little more light on my glue setup, I have a heating plate and thick pot that retains heat well. I made a chicken wire platform for inside the pot to hold the glue jars above the floor of the pot 1/2” and off the direct heat. One jar of water holds the thermometer to replicate the heat of the glue in the jars. For the center joints I’ve mixed the dry glue with cold water, let sit over night, heat the water up to 140 deg for an hour to make sure it’s holding the temperature steady, put the glue into the warm water for 15 minutes covered, stir with the brush, let sit covered until I’m ready to glue (15 min to an hour) As far as I know the thermometer never goes above 140. When I was ready to glue the top plates I uncovered the glue jar, stirred with the brush that’s been sitting in while water at the same temp (running off the brush in a steady stream like oil and breaking into drops just at the end of the stream, pull the jar out of water, poor a generous line down the joint, place the other board on top, rub out excess until I feel it bite, register ends and leave for a couple hours. 

And to be clear, I think most of the issues I was having with the back plate were with actually planing the joint straight in the maple and with issues in the clamping, both time wise and balancing the pressure of the grips to the wedges evenly. What made me feel better about the back was that I finally figured out those issues and had a seamless glue joint and cut offs that broke apart away from the glue line.

Luckily, now that the spruce has the outline cut out it would be pretty simple to clamp together again unlike before. 

Thanks again everyone for your feedback and putting up with the same beginner questions! 

 

 

Link to comment
Share on other sites

It seems to me Taylor that there is a wide variety of spruce used as tonewood.

Early makers such as those in Cremona often used alpine spruce with fairly thick and dense annual rings which lent a lot of strength and weight to the wood. And spruce I have used with those characteristics is quite different to North American or other European trees.

I've also got some Carpathian spruce which I got quite a long time ago which also has quite strong annual rings or reeds, but it has noticeably denser fast growth or lighter wood between the reeds. So it is probably on the high side of density.

Looking at your photos I see pale, silvery spruce with thin, closely spaced reeds which suggests to me that it is probably of low density. You could probably dent it with your fingernail.

So, it's just a matter of opinion what tonewood characteristics are best.

Talking about glue I've used rabbit skin glue for a long time. It's incredibly strong and probably as good as hide glue gets. I would avoid glue that is dark in colour, it might contain a lot of impurities.

 

 

Link to comment
Share on other sites

On 2/15/2021 at 10:28 PM, Taylor Sincich said:

For the maple joint I brushed thick glue and rubbed it in, whipped off excess, hair dryer then brushed glue, rubbed and clamped. I see some people glue size the joints before but I’m more worried about the spruce joint swelling or having too much glue than starving the joint.

If I understand correctly, this is an inappropriate system of gluing. If you want to use the glue-size, you have to put glue on both sides separately, and then let them dry perfectly (at least one night). Then re-plane the joint very lightly and make the final gluing (with or without clamps as you like, I prefer clamps).

If you glue-size and use the hair dryer immediately after without leaving enough time to dry properly, it will not be enough and the wood will remain swollen, compromising the perfect fit of the joint.

In my tests the 1:4 ratio works perfectly with my glue, it is the best compromise between bond strength and joint invisibility, but it strongly depends on the type of glue you use. With my glue a 1:3 ratio is too dense and always creates problems with visible glue line. This is why it is important to do some tests with your own glue to find the optimal ratio, without blindly trusting the tests done by others, even if they are always a good indication from which to start.

Link to comment
Share on other sites

5 hours ago, Davide Sora said:

If I understand correctly, this is an inappropriate system of gluing. If you want to use the glue-size, you have to put glue on both sides separately, and then let them dry perfectly (at least one night). Then re-plane the joint very lightly and make the final gluing (with or without clamps as you like, I prefer clamps).

If you glue-size and use the hair dryer immediately after without leaving enough time to dry properly, it will not be enough and the wood will remain swollen, compromising the perfect fit of the joint.

In my tests the 1:4 ratio works perfectly with my glue, it is the best compromise between bond strength and joint invisibility, but it strongly depends on the type of glue you use. With my glue a 1:3 ratio is too dense and always creates problems with visible glue line. This is why it is important to do some tests with your own glue to find the optimal ratio, without blindly trusting the tests done by others, even if they are always a good indication from which to start.

Thank you for your insight Mr. Sora and all of your videos and previous help. I understand your point. I had such a hard time planing the maple joint that once I had it perfect I didn’t want to let it dry over night and have to re plane it. I’ve also seen other posts on here that suggest NOT letting it dry more than overnight if sizing. I’ve also read that some people glue the joint and break it apart and re glue it all in one step. I went off this video by Peter Westerlund where he rubs the glue in first, wipes off excess and uses a hair dryer before gluing it again and clamping. To me it seemed the best way to make sure there was enough glue in the end grains to act like a sizing when I glued and clamped it.

Either way, I believe the glue joint for my back plate is acceptable and have moved on to creating the purfling platform.

Im aware my posts are probably too long but I outline all of the tests I did with my glue with different ratios, applications, clamping vs no clamps, etc. May I ask if you weigh the glue and water for your 1:4 ratio or is it by volume?

My question continues to be whether the glue joint on the top spruce plate seems sufficient or if the clean break suggests a poor glue joint.

8ADC02F8-863B-49AD-9B4E-F14078610302.thumb.jpeg.16fba1d08e19432bb4dfc95949264d4d.jpeg

 

 

Link to comment
Share on other sites

20 hours ago, Dennis J said:

It seems to me Taylor that there is a wide variety of spruce used as tonewood.

Early makers such as those in Cremona often used alpine spruce with fairly thick and dense annual rings which lent a lot of strength and weight to the wood. And spruce I have used with those characteristics is quite different to North American or other European trees.

I've also got some Carpathian spruce which I got quite a long time ago which also has quite strong annual rings or reeds, but it has noticeably denser fast growth or lighter wood between the reeds. So it is probably on the high side of density.

Looking at your photos I see pale, silvery spruce with thin, closely spaced reeds which suggests to me that it is probably of low density. You could probably dent it with your fingernail.

So, it's just a matter of opinion what tonewood characteristics are best.

Talking about glue I've used rabbit skin glue for a long time. It's incredibly strong and probably as good as hide glue gets. I would avoid glue that is dark in colour, it might contain a lot of impurities.

 

 

Thank you for your insight Dennis! A lot of good things to think about. For now, and since it is my first violin, I think I’m committed to the piece I have but will keep this all in mind for future projects if God willing I make it through this one!

Link to comment
Share on other sites

On 2/17/2021 at 10:27 PM, Taylor Sincich said:

Thank you for your insight Mr. Sora and all of your videos and previous help. I understand your point. I had such a hard time planing the maple joint that once I had it perfect I didn’t want to let it dry over night and have to re plane it. I’ve also seen other posts on here that suggest NOT letting it dry more than overnight if sizing. I’ve also read that some people glue the joint and break it apart and re glue it all in one step. I went off this video by Peter Westerlund where he rubs the glue in first, wipes off excess and uses a hair dryer before gluing it again and clamping. To me it seemed the best way to make sure there was enough glue in the end grains to act like a sizing when I glued and clamped it.

Either way, I believe the glue joint for my back plate is acceptable and have moved on to creating the purfling platform.

Im aware my posts are probably too long but I outline all of the tests I did with my glue with different ratios, applications, clamping vs no clamps, etc. May I ask if you weigh the glue and water for your 1:4 ratio or is it by volume?

My question continues to be whether the glue joint on the top spruce plate seems sufficient or if the clean break suggests a poor glue joint.

8ADC02F8-863B-49AD-9B4E-F14078610302.thumb.jpeg.16fba1d08e19432bb4dfc95949264d4d.jpeg

 

 

Westerlund's method doesn't convince me at all, but I've never tried it (and don't feel the need to) and it obviously works for him. But he makes Guarneri copies, maybe he also wants to imitate the inaccuracy of the joints...:lol:

I don't use the glue-size just to avoid having to do the job twice, I consider it admissible only in the case of woods with particularly twisted or absorbent grain in which case it might be worth it, but I always try to avoid woods that are too "bizarre". If this were the case, I would reconfirm that I would have the glue-size dry completely (8 hours or more) to stabilize the wood before proceeding with re-plane and gluing the joint.

My glue to water ratio is by weight.

Regarding your last photo, in my opinion it is not strictly necessary that the glue is so strong so the test piece break on wood only, some separation at the level of the glue line I think is acceptable to some extent. The example of your photo is a bit too much, I would expect a less clean separation on the glue line, but what matters is the strength needed to cause this separation, not the separation itself. If it opens easily it is worrying, but if it puts up a lot of resistance before opening it is probably ok. In real working conditions the violin is not subjected to such exceptional loads and bending force, and a good distribution of the arching curve ensures that the load is not concentrated only on the central joint like when you do the breaking tests with your hands on test pieces. If this were the case, reinforcement cleats on the joints would have long since become a standard procedure even on modern violins.

Disclaimer: :)

this is just my way of thinking about this subject, if you want to be 100% sure of the resistance of your joints even under extreme loads, I think the 1:2 glue-water ratio is the one that guarantees the greatest resistance, all other dilutions are compromises between strenght and aesthetics (glue line visibility).

Link to comment
Share on other sites

On 2/19/2021 at 8:28 AM, Davide Sora said:

But he makes Guarneri copies, maybe he also wants to imitate the inaccuracy of the joints...:lol:

Haha!

On 2/19/2021 at 8:28 AM, Davide Sora said:

My glue to water ratio is by weight.

Regarding your last photo, in my opinion it is not strictly necessary that the glue is so strong so the test piece break on wood only, some separation at the level of the glue line I think is acceptable to some extent. The example of your photo is a bit too much, I would expect a less clean separation on the glue line, but what matters is the strength needed to cause this separation, not the separation itself. If it opens easily it is worrying, but if it puts up a lot of resistance before opening it is probably ok. In real working conditions the violin is not subjected to such exceptional loads and bending force, and a good distribution of the arching curve ensures that the load is not concentrated only on the central joint like when you do the breaking tests with your hands on test pieces. If this were the case, reinforcement cleats on the joints would have long since become a standard procedure even on modern violins.

Disclaimer: :)

this is just my way of thinking about this subject, if you want to be 100% sure of the resistance of your joints even under extreme loads, I think the 1:2 glue-water ratio is the one that guarantees the greatest resistance, all other dilutions are compromises between strenght and aesthetics (glue line visibility).

Thank you so much for your time and opinion Mr. Sora. That was exactly the type of feedback that I was looking for. I understand I am bypassing the cost, time and dedication it traditionally takes most to learn this craft and am essentially asking for trade secrets for free with nothing for you in return. For that I am truly thankful and and in your debt. 

I also haven’t heard of others using Westerlund’s method but for now I cross my fingers and hope it works out on the back. Luckily, It did not have significant end grain along the joint and the cutoffs seem to be strong so I feel comfortable with it. 

I understand your point that it’s not necessarily just that the pieces broke along the glue line but by how easily they broke apart that is also important. Because they did break so easily, and because of the clean break, I’ve decided I’ll saw it apart and re do the joint today. I’m still going to try a 1:3 mix because my tests showed it to be the best mix of strength and visibility for my glue but will use clamps this time. I’m not sure if I’ll have enough to make any cut offs from it but maybe I’ll get a sliver off the ends. 

Thanks again for everything and i will report back after!

 

Link to comment
Share on other sites

I haven't read the whole thread Trevor, but next time an easy way to do this is to mount your jointer in a vise upside down and take both halves of your top and draw them down over the blade with light even pressure. (Your blade needs to be flat and as sharp as you can get it). Any inaccuracy from left to right will cancel out. be careful not to apply two much pressure at the beginning and end of each pass over the blade. Test accuracy by putting one half in the vise and use the other half to test for front to back and side to side (there should be no rocking). If it is a perfect fit you'll feel a bit of suction as you place the two pieces together. Make a pencil mark across the front so you know where to line up when you glue.

Once you have a perfect joint - especially with spruce you have to glue it right away. So your glue has to be ready once you finish the joint. Any change of humidity and temperature can really mess with you. I warm both sides with hair dryer and pour the glue on the joint with a squeeze bottle. Rub the two halves together for a bout 10-15 seconds and ensure your pencil lines up. No need to clamp - leave it in the vise standing up for a couple of hours and plane flat.

I highly recommend @David Burgessarticle on working with hide glue published in the Strad. One of the best in the trade secrets series. Once I started following his guidance, gluing became a lot let stressful!

Link to comment
Share on other sites

Looks to me Taylor that you are doing just about everything right. Looking at your photos you have a planing routine that works as well as it should. Going by your comments though I get the impression that you might be overdoing the rubbing.

I think that pouring glue along one half clamped in a vise, placing the other half over it at an angle and then swinging the two into alignment and finishing with a short back and forth movement is the best way to go. Don't use much pressure at all, concentrate on aligning the two halves and stop any sliding action as soon as the two halves grab.

If your workshop is reasonably warm I don't think you need to use a heat gun.

I've never had any issues of joint separation using hide glue. In my experience the wood always splits before any glueline failure, whether the joint is perfect or not.

 

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
 Share

  • Recently Browsing   0 members

    No registered users viewing this page.



×
×
  • Create New...