Guest Luthier Blog
This is a new category to my blog. It allows guest luthiers to submit comments, tips, tricks etc. to me and I will place them on my blog in the Guest Luthier Blog category. So, if you have something to offer that you think others can benefit from then please send them to me. Things need to be well written and documented with pictures when possible.
Here is the first "tip" submitted by my former student, Denny Brown. It addresses the problem of how to fix dings in soundboard material. Denny writes a blog called "My Guitar Notes" from his website FlatironFrets.com. He has also written two books that accompany my online guitar building courses.
Rescue: Top Dents
By Denny Brown
It's a sickening feeling in guitar building. Maybe one of you fingernails angles across your freshly sanded guitar top, or a tool slips out of your hand. Even worse, something falls off of the shelf. Doink. Dent. Can this be fixed? Could it have been prevented? The answer to both questions is probably "yes"
After joining the top, cut out a piece of poster board to fit the top. Poster board is sold at office supply stores. Keep it taped to the outside face of the top, removing it as necessary. The poster board is trimmed to fit to the top as it changes shape while building the guitar. Make sure to brush off the top when reapplying the poster board to the top. Anything trapped between the top and poster board can damage the top. You can use the poster board through protecting the finish during string installation.
Put It Somewhere Safe
Keep the top in a cardboard sleeve before it is attached to the body. Once the top is glued on, find a safe place in your shop for the body to live. My shop is too small (whose isn't?) for "safe places". So, I keep my unfinished guitars in a gig bag. (Until the neck is carved, the guitar won't fit into a regular case.)
Lift Dents and Cuts
Most dents are easily fixed if the wood fibers aren't broken. A drop of water in the dent will expand the wood fibers and lift it out, ideally over correcting the problem. Then, sand it smooth.
If a few applications of water don't work, use steam to penetrate into the wood. Place a damp folded piece of paper or cloth towel over the defect and touch the iron to the towel to generate steam. Touching the wood directly can scorch it.
Cut fibers generally don't swell shut with water. However, water may raise the wood fibers beneath the cut, so the cut portion can be sanded away. Be careful not to sand the top too thin!
I resort to "Second Chance," from LMI, when water and steam fail. It comes in two wood colors (spruce and cedar) with three shades each. Mixing shades can produce a good color match. Use a cutoff from your top as a test piece.
Cyanoacrylic (CA) glue makes a clear filler. It should not to be used on bare wood, especially spruce, because it stains. Use it over a few layers of finish.
After the first round or two of French polish, I use CA glue to fix the imperfections in every classical guitar rosette. CA glue can also be used for other low spots on the guitar. Drip thin viscosity glue onto the defect until it is slightly overfilled. It will self-level as it air dries. Do NOT use accelerator or the glue will foam. Scrape the glue level with a razor blade. The unneeded portion of the blade can be covered with tape. Lightly sand up to 1200 grit, and resume finishing.
How do you fix dents and cuts? Leave a comment.
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