"Interesting" top crack issue

[Brian Stewart]

Hello folks,

Customer brought me a 70s era Ovation for repair (red lights and sirens are going off, I know...).  It is a Glen Campbell model with a nice top crack in the usual place....about 3/4" to the side of the center seam extending from the back of the bridge to the tail block.

What is causing me to think harder about this particular crack is that it is quite open and won't close shut...but it does not go all the way through the top.  I can feel a crease on the inside where the crack is.  Looking closely I can see it as well, but it is definitely not open all the way through the thickness of the top.

I'm pretty much resigned to having to spline this crack, but thought I'd see if anyone else has run into this and maybe tried a different solution. 

One idea I had:

-Try to cut through from the inside, along the crease, in the hopes that the crack will then close from the top. This would also allow glue to penetrate the crack and also make cleating effective.  I like this idea.  I think if it didn't work, splining would still be an option.

I have tried hydrating the top and yes, this is a solid topped guitar.

Look forward to hearing your thoughts.

Brian

[Hesh Breakstone]

Hi Brian:  We turn Ov*tions away for reasons such as these but it sounds like you knew what you were in for.

One of the guys at Elderly has been pioneering a technique of using of all things ep*xy with color tint to fill some cracks and then it's cleated from the inside.

A guitar of this vintage AND with a rim that is as stiff as an Ov*tion back and sides is not likely to close with RH manipulation.  So in my view filling one way or another are really the only options.

Since Ov*tions likely already have 7 pounds of ep*xy in and on them.... filling with ep*xy likely won't make this one sound any worse than it already does. :)

The technique has us cleaning up excess ep*xy before it's dry with a paper towel, no solvents.  When cured it's scraped or wet sanded back to level.  Finally it's cleated.

You do have to give this some thought before diving in since ep*xy has it's own risks associated with not being able to clean it up well and this technique is not for every instrument.  For an Ov*tion though it might just help you out.

Also you can test if the crack goes all the way through by dropping naphtha with an eye dropper on the crack and then looking inside for the wet.... spot....

[Paul Breen]

The way you describe the crack just seems unlikely to me. Are you sure that the crack isn't angled, not perpendicular to the top? I like using a good light source inside of the instrument, placed under the crack location and looking at it from different angles.

I have also had good results closing open cracks by going a step further than just hydration. I use a whetted rag or brush and liberally wet (not dripping) the underside of the top from bout to bout on both sides of the crack location. Usually takes several applications and an hour or more. I have done this to vintage and new instruments and never had a finish problem arise from forcing the forcing the issue this way. Probably worth a try before splinting or epoxy.

[Hesh Breakstone]

Hey Paul:

Our experience with rehumidification is evolving so that lately we are doing some things a bit differently.

The problem that we seek a solution for is not closing cracks with humidification it's also addressing the inherent permanent dimensional instability that exists to some degree in many instruments.

We will bag a cracked guitar at around 75% for 2-3 days and watch the crack close, usually.... some won't close even at this level of humidification.

Then we would glue shut, cleat and call it a day.  We've learned that although our repaired cracks never come open again some instruments will then crack somewhere else because of the permanent dimensional distortion.

As such these days we will bag em and tag em for around 3 days then then remove them from the bag and hang them in 45 - 50% shop for a couple more days.  If the crack opens up again at normal RH forcing it closed and cleating is not as reliable in our experience as filling with wood.  I'm not advocating the ep*xy fill by the way just wanted to mention it as an option for some instruments, not all.

Although our new approach takes a couple of days longer we believe it to be more reliable.

[Paul Breen]

Hi Hesh,

Thank you for your comments and observations.

I live in Central Illinois and rarely get a crack repair here, except in the winter. The weather can be quite fickle, sometimes warm and balmy but then plunge below freezing, the most likely time for an instrument that is not being looked after with proper humidity levels to develop a crack. Summers here, on the other hand, never seem to be lacking abundant humidity.

You can take a perfectly stable instrument, starve it of moisture and tensions will start to build. First top deformation and ultimately failure by splitting open. Bob Taylor demonstrates this in one of their training videos. An instrument is placed in an environmentally controlled box, the humidity dialed down and they observe the results. It doesn't take very long for change to happen and the instruments geometry is out the window followed usually by open cracks. If you don't let it go until cracks form, the distortions to geometry can usually be reversed and tensions relieved with re-humidification.

Vintage material doesn't always conform to this observation. Years of tension building from tops and backs shrinking at right angles to the sides and vice versa. I look at instruments as having unique personalities, all a bit different in how they age and respond to therapy. I approach them pretty much the same way though when building a case to splint or not. Some can be submissive while others seem to pull and buck at the lead.

When I have instruments come in with hydration issues, they get two, large size Dampits into the sound hole and are either left in the case a couple of days or get bagged if they have a crappy or no case. This does not always close an open crack though and clamping it closed at this point will cause some tension.  By whetting the underside of the top, bout to bout, mostly adjacent to the crack, I am essentially over humidifying the instrument. If this does not close it, nothing will and it needs a splint. If it does, I glue it up, cleat it and let it dry out slowly to reach an acceptable humidity range with the sound and bridge pin holes taped closed. I have not run into an instrument that has cracked from over humidification unless it had been in a flood or the like.

I only use hot hide glue for crack repair with few exceptions. If something doesn't go well and I do need to splint or re-do it, I haven't crapped it up with some difficult or impossible to remove glue. I use an Infra Red lamp to keep the area of the crack warmed up while I work some watery thin hide glue in until I see it whetting the underside of the top along the length of the crack. With the Infra Red lamp and watery thin hide glue, there is NO hurry. Once it's worked in, I follow up with another dose of hot hide that is thicker. Maybe not necessary or over kill with the follow up with the thicker stuff but repair work is all about putting the odds in your favor. The crack will be pretty much self clamping when closed but I always put a length of plexiglass over the glued crack and use light clamping pressure clamping on the plexi, top to back on the outside of the instrument. A whetted crack will swell the most along the edges of the crack, this helps keep the outside edges aligned and helps it to dry completely flat. This doesn't always ensure proper crack alignment, I always check first with a practice clamp up and modify if/as required to do the job correctly.

My humidity issue customers get a lecture when they come back about the importance of proper humidification but some of them are repeat offenders. Not much you can do about that except try and educate them.

Epoxy IS in my bag of tricks but I have never used for any kind of wood to wood crack repair.

[Hesh Breakstone]

Hi Paul and many thanks for one of the best posts that I have read in a long time!

I'm going to give your HHG, first thinned and then full strength with heat lamp assistance a try.  Your justification of not having to clean out old glue if the repair fails is a very good justification.

I've not see the Taylor video that you describe but will ask my business partner, Dave Collins if he has since he went though the certification process.

Thanks again Paul, much appreciated!

[Paul Breen]

Gee, thanks Hesh...

There is a learning curve for sure becoming effective with hot hide glue. If I was not into facing new challenges though, I would certainly not be doing any instrument repair!

[Hesh Breakstone]

Thanks Paul.  We use HHG near daily so I'm well versed in it's use and learning curve.

One of the reasons why I have preferred Titebond Original for top cracks is that HHG if not used under heat as you suggest tacks quickly making getting the two sides of the crack perfectly level a juggling act.  

Your suggestion of using it under a heat lamp buys me some time AND I really like the idea that I can reactivate and no need to clean out of the crack if repair fails going forward.

We repair over 1,100 guitars, mandos and banjos annually and turn away slightly more that this.  We are a two person shop with a brick and mortar set-up and have lots of clients including some famous ones.  Our web site might be worth a look specifically the reviews which I try to keep up to date.

We've fancied the idea of a hot room for HHG use like the violin folks do but neither of us wants to see the other in our boxer shorts...:)

As such no strangers to HHG here I just never considered using it under an active heat lamp and I thank you kindly for that idea.

Take care.

[Andrew]

On my latest job Ive been putting a 30 watt incandescent bulb inside under the crack to keep the area warm. I wrapped the bulb on three sides with that silver bubble wrap type insulation stuff to keep heat off anything that doesnt need it. A little pre heating with a hair dryer gets things started, then the bulb keeps it there pretty nicely. I suppose one of those long cabinet type bulbs would be good for longer cracks. This seems to be very controllable.

Also, using thinnish hide glue and a suction cup to push it in, Ive been able to get some pretty tight cracks saturated in a hurry, without rubbing my grubby fingers all over it.

[Paul Breen]

"We've fancied the idea of a hot room for HHG use like the violin folks do but neither of us wants to see the other in our boxer shorts...:)"

I used to own a house that had bathroom with a forced air heater in the ceiling and would use it from time to time as a hot room for hide glue projects. Turn the heater on with my project in there, shut the door and let it get up to around a 100 degrees. You made me laugh remembering going in there to work with just under pants on!

The Infra Red lights work quite well and If I need the heat spread out more, I use more Infra Red lights. Telescoping stands work great and are versatile when used with clamp light fixtures.

[Brian Stewart]

Thanks for the responses and info. I ended up splining the crack. Spline turned out fine, just have to get the finish right now! 

The crack did go all the way through, but was pinched tight on the inside, creating a crease where the crack was...kind of like it was being pushed together from the sides hard enough to deform the top...I don't know.   If I pushed down on the top hard enough, it would open a bit - on the inside - in certain spots, but not others.  It never would close tight on the top.  

Anyway, on to the next step.  Thanks!

[Paul Breen]

Glad you got it done, thanks for sharing the results.

[Doc Rathwell]

Just finished up the crack repair on this nice double top made in Brazil...lucky me gets to see LOTS of Crack repair up here in Canada.

I only ever use HHG. This guy was rehumidified, set in a 45%RH environment for a week to make sure things were good then on to the repair gluing. Piping hot HHG used, no touch-up required (French polished instrument) and no cleats...though I will certainly use cleats if I feel the need.

Cheers,

Doc