Official Luthiers Forum!
http://www-.luthiersforum.com/forum/

Glued My Bridge Caul To The Bridge Plate
http://www-.luthiersforum.com/forum/viewtopic.php?f=10102&t=11146		 Page 1 of 1
Author:  LarryH [ Fri Mar 02, 2007 11:04 am ]
Post subject: 
For real. Somehow got some glue between the caul and bridge plate while gluing on the bridge. I drilled some holes through the pin holes and screwed some wood screws into a caul under the bridge.

Some glue must have snuck through a hole or two and gotten between the caul and bridge plate. LMI white and it will not budge. I tried prying but I could damage the X brace too easily.

Please, no techniques describing the use of wax paper - I've done it this way before with no problems - this time I just left it out, and am really stumped with this one. The good news is it is probably glued in a very small areas(s).

I also used double sided tape to locate the caul which has always been hard to disengage, but this time I feel there is definitely some glue.

The only way to try and pry it off is with a chisel held against the X brace or by hand. Neither is working.

Help?

Larry
Author:  Shane Neifer [ Fri Mar 02, 2007 11:12 am ]
Post subject: 
Larry,

Two options, first, coninue pryiing but place a piece of scrap wood over you X bracce to distribute the loadand protect your X from damage from the chisel. If it does not pop off then you will have to get some heat involved. With heat you can try just heating the caul and seeing if will come off but you may actually have to heat from the top and take the bridge plate off of the top and then the bridge plate off the caul.

Good luck

Shane
Author:  JJ Donohue [ Fri Mar 02, 2007 11:42 am ]
Post subject: 
Have you drilled the 6 holes yet?
Author:  David Collins [ Fri Mar 02, 2007 11:54 am ]
Post subject: 
The glue is obviously only around the holes that were drilled all the way
through, right. I would carefully shoot some steam in to the bridge pin
holes. 30 seconds of intermittant steam would not be enought to swell the
wood or loosed any solid glue joints, but it might be just enough to loosen
the grip in those small spots.

I suppose the severity of this could depend on whether glue got in to the
holes before or after the caul was seated firmly against the bridge plate. If
the caul was firmly seated first, then the glued surfaces should not extend
much beyond the holes themselves.
Author:  LarryH [ Fri Mar 02, 2007 12:07 pm ]
Post subject: 
[QUOTE=David Collins] The glue is obviously only around the holes that were drilled all the way
through, right. I would carefully shoot some steam in to the bridge pin
holes. 30 seconds of intermittant steam would not be enought to swell the
wood or loosed any solid glue joints, but it might be just enough to loosen
the grip in those small spots.

I suppose the severity of this could depend on whether glue got in to the
holes before or after the caul was seated firmly against the bridge plate. If
the caul was firmly seated first, then the glued surfaces should not extend
much beyond the holes themselves.[/QUOTE]

Yeah David, you got the picture exactly, this is most likely the case. Small amount of glue around each (or a couple) hole possibly. I drilled out each hole all the way hoping that it would loosen the glue around that small area but no luck so far.

I thought about inserting some moisture in the holes to try and loosen those small areas and steam would be
ideal.

Is there a chemical like alcohol or lacquer thinner that might be placed through the holes and just on the joint between the caul and plate?

Looks like a long weekend. Thanks for the advice.
Author:  LarryH [ Fri Mar 02, 2007 12:26 pm ]
Post subject: 
[QUOTE=JJ Donohue] Have you drilled the 6 holes yet?[/QUOTE]

Yeah JJ,

I at first thought I would back the screws out about 1/2" then push the caul down and off the plate. That didn't work. Then I drill out all 6 holes to try and loosen the glue around the hole - no good so far.
Author:  Rod True [ Sat Mar 03, 2007 2:38 am ]
Post subject: 
Larry, did you drill completely through the caul?

If not you could fill the hole to the bridge plate with vinegar, that should also loosen the glue once it weeps in between the bridge plate and clamping caul.

But I think David's suggestion is the best so far.
Author:  Dave White [ Sat Mar 03, 2007 3:03 am ]
Post subject: 
Larry,

I used to use double sided tape to hold the bridge plate caul and found that once clamped that stuff sure could hold and getting the caul free was not easy. I gave up this method after using it on a small travel cittern with tiny sound hole. It took me 4 days of gentle rocking - and a sore hand - to get that caul loose

If you didn't use a brace behind the bridge plate then perhaps you could uze a thin razor blade to try and push this carefully in between the bridge plate and caul where the holes are to try and break the glue bond. Or perhaps a thin pallete knife that you would use to remove a bridge. This will require some dexterity inside the box to get your hand to manipulate it at the right angle, lots of patience and care and a soundproof room to trap all of the expressions like "Oh ... bother" that will emerge.

Good luck.
Author:  JJ Donohue [ Sat Mar 03, 2007 3:18 am ]
Post subject: 
This is a real "character builder", Larry. Dave used the word that serves us all well when we encounter these situations...PATIENCE! Just walk away for awhile when you're losing it.

We've all been there and most of the time it all works out. I believe that David and Dave have some good suggestions...just take your time and go slowly.

If you need any good expletives to help coax the caul away, just let me know...I've used them all!

Keep us posted...you've got lots of friends rooting for you.
Author:  crazymanmichael [ Sat Mar 03, 2007 3:57 am ]
Post subject: 
i know it is not helpful now, but using wax on any caul which might adhere to your glue is insurance in such circumstances, as is making your cauls out of the high density polyetylene.

heat and the vinegar seem like your best options at present.
Author:  LarryH [ Sat Mar 03, 2007 4:03 am ]
Post subject: 
[QUOTE=Dave White] Larry,

I used to use double sided tape to hold the bridge plate caul and found that once clamped that stuff sure could hold and getting the caul free was not easy. I gave up this method after using it on a small travel cittern with tiny sound hole. It took me 4 days of gentle rocking - and a sore hand - to get that caul loose

If you didn't use a brace behind the bridge plate then perhaps you could uze a thin razor blade to try and push this carefully in between the bridge plate and caul where the holes are to try and break the glue bond. Or perhaps a thin pallete knife that you would use to remove a bridge. This will require some dexterity inside the box to get your hand to manipulate it at the right angle, lots of patience and care and a soundproof room to trap all of the expressions like "Oh ... bother" that will emerge.

Good luck.[/QUOTE]

That nails the problem EXACTLY. That stuff can STICK and I think it is what's holding the plywood caul - not any glue. An added problem is that there is a brace behind the plate and the caul fits really well between the X and that brace so very little room to get in there.

Character builder? I love that. It might take the whole weekend but I'll get this little @#$% off. I just don't want to ruin the top when it's do close to being strung up.

Author:  SimonF [ Sat Mar 03, 2007 4:04 am ]
Post subject: 
Larry, denatured alcohol will dissolve LMII white glue. Just be careful to
not flood the area with it. Whatever you do - just go slow and don't rush
it.

Best of Luck,
Simon
Author:  David Collins [ Sat Mar 03, 2007 5:38 am ]
Post subject: 
I don't know too much about the LMI glue, but the vinegar solution
suggested is traditional for hide glue, and I don't think it will do
much for cured PVA's. Simon's suggestion seems better. I don't know if
the LMI is a polyvinyl acetate, or a polyvinyl alcohol, or some mixture in
between. I do know that denatured alchohol works excellent for softening
polyvinyl alcohol glues, though I don't know it's effect on acetates. Like
Simon said though, don't flood it. Ideally it would be nice to only touch
the plate/caul joint, without effecting the plate/top joint.

Still if it were me and the holes weren't drilled all the way through the
caul I would just grab my steamer and I bet it would be off in no time.
If it's any consolation, I've often considered starting a collection of all the
repair cauls I've retreived from customer instruments that were just left
there by previous shops.

I rarely use tape to hold a caul in place, but I always use it to hold waxed
paper to the caul. Most of the time I can hold it in place with my hand
until at least one clamp is in place. What most people don't realize about
most tape adhesives is that, like glues, the bond doesn't develop
instantly. It often continues to strengthen for hours, to days to weeks.
The longer you leave it on (especially under clamping pressure) the
harder it will bond. If you do use tape, at least rub the side that you want
to come loose against your shirt and hands a few times. Remove, or
rather contaminate some of the tack and it will still hold the caul in place
for you, but will release much easier. And always, always use waxed
paper.

Author:  LarryH [ Sun Mar 04, 2007 1:55 am ]
Post subject: 
GOT IT OFF!!

Hey first of all thanks very much as usual for all your help. I hope this helps some one else in the same predicament.

[quote]What most people don't realize about most tape adhesives is that, like glues, the bond doesn't develop instantly. It often continues to strengthen for hours, to days to weeks. The longer you leave it on (especially under clamping pressure) the harder it will bond.[/quote]

As soon as I realized it was the tape holding the plywood caul I understood what had happened as David described above. That stuff is tenacious as all get out. So I reached in every 2 hours and pulled until my little fingers were sore, just so the bond would not get any tougher.

I couldn't feel any movement but in the meantime I purchased this really small 6" long or so prybar and was able to just get it under the edge of the caul. I didn't lift with too much force but slowly forced it in and the tape let go!

What a huge relief. Any way as always thanks so much for the advice - especially the be patient stuff.

Larry
Author:  JJ Donohue [ Sun Mar 04, 2007 2:06 am ]
Post subject: 
Congrats, Larry...you passed the patience test and were rewarded!

Now...get busy and get that baby strung up. I can't wait to see her finished!
Author:  RobertJeffery [ Sun Mar 04, 2007 4:20 am ]
Post subject: 
Larry,
I can finally stop holding my breath...

good for you!
Author:  Rod True [ Sun Mar 04, 2007 5:36 am ]
Post subject: 
Well done Larry. I bet your fingers are sore.
Page 1 of 1 All times are UTC - 5 hours
Powered by phpBB® Forum Software © phpBB Group
http://www.phpbb.com/