Sealing the Body – Guitar Making Tips

One of the most important steps in guitar making is sealing the body. On the body, there should only be one place where air can escape, and that’s the soundhole. As you assemble the sides and the plates, sealing the body well means a better sounding instrument. Here is how you do it.

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Guitar Making Tip No. 12 – Sealing the Body

sealing the guitar body guitar making tipsOf all the different steps in guitar making, sealing the body is one of the most important. If you seal the plates to the sides well, the guitar will function better, and sound better to.

Thankfully, getting a really good build on the body is not terribly hard.

It does require some prep work on your end, and probably at least a few dry clamping runs without any glue. I explain why it’s harder to fix Glue Covered Problems in another article.

The better you prepare the plates, and more specifically the brace ends, the easier it will be to get a good seal on the guitar body. As with most things, the details are what counts. You are going to have to spend some time fitting the plates to the sides in order to get the easy gluing seal that you are looking for.

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Prep Work for Gluing the Body Together

sealing the guitar body guitar making tipsFor guitar makers that use an outside mold, the top plate is often glued on first. This is good, because the brace ends on this plate are more interesting to work with.

You can get the hard part out of the way, and then the back plate will be easier.

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Decide whether your braces are going to go under the kerfing, or if they are going to terminate at the kerfing. This will determine how you are going to handle the fitting. If you are running the braces under the kerfing, you need to mark where they cross. Then, use a Dremel or a chisel to remove some of the kerfing so they fit underneath.

If you are butting them up to the kerfing, then look inside the body mold and mark where the braces touch the kerfing. After that, saw the excess, and chisel it off.

I recommend running the braces under the kerfing. This helps hold them in place because the kerfing will become a physical barrier to them lifting. It does take more time, but I believe the reasons are worth the effort.

If you like guitar making, check out Acoustic Guitar Making for Beginners, which highlights the best parts of my massive 508 page acoustic guitar making book.

Attaching the Back Plate to the Body

sealing the guitar body guitar making tipsThe back plate is going to require the same process that you did on the top.

Decide on your method, and make the cuts to create clearance when the pate is placed against the sides.

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As you are fitting the plates, be sure to check that the pieces fit against each other flush. The wood should touch without any gaps, and it should not require a ton of force to seal. If you really have to press or force the pieces, then you need to look at where they are missing and make some adjustments. This could be as simple as taking a little off a brace, or removing a little more kerfing.

Gluing the Plates and Sealing the Body

sealing the guitar body guitar making tipsWhen you have your seal, do a dry run with both plates and see how they look. You should be able to place every clamp easily, and without fighting the guitar body.

After all the clamps are in place, look around the body for gaps. If you find any, address them. If you do not, you are ready for glue.

Apply glue to one side of the guitar, along the kerfing and the edge of the sides. Spread it evenly with a finger or glue roller. Then, attach the plate. Make sure it presses into place correctly, and start adding clamps. Make sure to use a ton of clamps, and space them as close as you can for even pressure.

After you have them all in place, tighten them down enough to seal the box. Check for gaps again, and wipe off any large amounts of glue squeeze out. Allow the guitar to dry and then do the same thing with the other plate.

Now, you have a good seal on your acoustic guitar soundbox. This is important for the way the guitar functions, and will ensure that you are not losing air through gaps in the body.

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2 thoughts on “Sealing the Body – Guitar Making Tips”

  1. With regard to sealing the top and bottom plates, I used to build boats and epoxy is the choice because not only is it strong but gap filling. By mixing a thickened epoxy you can fill many gaps. Is there a reason the luthiers seem to avoid epoxy, and use wood glue exclusively?

  2. Thank you Paul. Guitar makers avoid epoxy in some cases, but they definitely use it for others like inlay work and gluing oily woods together. For the body, most guitar makers frown upon having gaps that need sealing with a product other than wood glue. The idea being that if you are failing to make a good joint, you should just work harder on that joint and get it right rather than relying on a filling product. I have always taken a more middle of the road approach and I believe that using modern adhesives in a traditional instrument is not a bad thing. As long as you are making a good joint, and not using the epoxy to overcome a terrible fit, then all you are really doing is using an incredibly strong adhesive in the place of wood glue. In that sense, you can’t go wrong. For the record I do not use epoxy for the body sealing, but if your plates fit well, you can use either wood glue or epoxy successfully. Let me know if you have any additional questions, and happy building.

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