Crack Repair

What Caused My Acoustic Guitar To Crack?

A washboard texture which looks somewhat like corduroy is one of the first signs of dryness.
It is very important that you know how to recognize this and what to do about it should your guitar start to show these signs of dryness.
In the picture below the soft spruce top has lost a great deal of moisture and the dark grain lines now stand prominent, the ridges are noticeable to the touch.

Cracking is likely if the problem isn't addressed and its dry season continues.

A dried out spruce top often
resembles corduroy.

Tops are build with radius or arch. As the instrument dries out this arch will flatten and the washboard texture may already be noticeable.

If humidity is low and the instrument continues to dry out the arch will flatten and can become concave when terribly dry.

If your instruments top begins to dip and become concave without cracking you're pretty lucky, now is the time to begin humidifying.

The majority of instruments that are truly dry will crack the top first , very dry instruments can also split along their sides or seam lines.
On one of those, a good rap or bump to the side can result in the side splitting wide open, not a pretty sight.

Common Signs of Dryness

Straightedge reveals concave guitar top.

Repairing Cracks

While some cracks are relatively easy to repair it's important to realize that are often a one shot deal. When repairing cracks it is essential that the separated halves are well aligned and the work is done cleanly.  Reversing a bad repair is far more difficult and expensive than having it done correctly to begin with.

When repairing most cracks I like to have a caul on the inside and outside of the instrument that keeps both sides of the crack aligned while gluing.

Cracks Near The Pickguard

Several manufacturers employed the process of attaching the pickguard directly to the bare wood of the top before spraying the instrument.

Unfortunately these shrinking celluloid pickguards can cause a problem. If they maintain a good grip on the top while shrinking it places formidable stress on the top. If the pickguard shrinks considerably a crack can develop on either side of it.

To repair these cracks the stress must be eliminated by removing the pickguard and reattaching or replacing it. In an effort to avoid a repeat, and keep the new adhesive from pulling up wood fibers if removed again, this bare area of wood beneath the guitar is usually sealed with finish. View a Martin Pickguard crack repair.

Finish Repair

The real challenge to repairing most tight cracks is primarily with the finish. Stripping and refinishing the entire panel to render an invisible repair on a small crack would be overkill to say the least. Depending on the crack, finish repair may not be advisable or necessary.

Glued cracks still leave a small valley in the finish. When repairing cracks it is usually a two part process; repairing the crack in the wood, and then repairing the finish.

When repairing lacquer finishes a new lacquer "fill" is placed in the finish crack. This lacquer fill will begin to shrink almost immediately and a small depression is likely to appear, even after weeks of patient waiting. Lacquer is very high in solvents and it shrinks quite a bit.  For this reason small chips, sink marks and cracks can reappear after a flawless repair days or even weeks after it has been done. I try and educate my customers to the nature of wood and  lacquer so they understand what is possible.

damaged guitar top

Taylor guitar damaged by impact.
Photo of completed repair

Cracks That Will Not Close

More often than not, cracks that have spread open and will not close with humidity are spliced, filled with a inlay of wood. This dilemma is usually only found on older, very dry instruments, perhaps something that was left in a very poor environment. But there are other causes that can create the need for a splice, like something that has been damaged and wood is now missing or an area that is under so much stress that closure is not possible.
A splice is an insert of wood, like a filler strip, that is inserted into the area that is open. If the crack that is being repaired does not follow a straight line but runs across the grain the splice is much wider as a symmetrical splice must be used.

What about just filling the crack with putty, wouldn't that be easier? Oh my, would it! However, I don't do it. Putty and wood filler is not an acceptable repair method in most cases. While there are obviously some repairs that may require it, wood should be replaced with wood. Putty will shrink and usually just doesn't look right. Obviously on something very inexpensive, splicing or wood replacement can easily exceed its value.

My Guitar Cracked, Now What?

If there is any chance that the crack is related to dryness you should begin humidifying the instrument.

The best time to repair a crack on your instrument is before it has time to accumulate dirt and grime or worse, run like a bad pair of panty hose! (Sorry guys ...a Pinto on Nitrous?) If string tension puts stress on the crack you should remove it immediately.

Cracks that go un-repaired can sometimes cause more serious issues, especially if it causes the wood to warp and twist out of alignment.

If string tension stresses the area of the guitar that is damaged or cracked it should be removed until a repair can be made.

Cleats

Cleats are normally made from the same material as the panel which they are reinforcing. While there are some repairs that require reinforcement, I avoid cleats unless absolutely necessary, especially on clean cracks. As I point out to my clients, every guitar has a top and back crack...tops and backs are made from book matched wood, two pieces of wood glued together down the center. This is a glued seam and is not cleated. (The center strip used over many back center seams is there to reinforce the area when the back is routed for a center strip.)

Cost

Whether caused by impact or dryness, cracks can effect the braces as well. The alignment, finish damage and ease of closure all contribute to the overall cost.

I offer free estimates to those desiring to have them repaired, I can not offer estimates based on pictures alone.

Copyright © 2012 Fret Not Guitar Repair Inc.
Site Map | Privacy