Addressing Glue Bleed-Through on Veneer Tops
Building a kit guitar with a decorative maple veneer top can really add to the look of
the finished guitar, but it also introduces the potential for a common finishing pitfall:
glue bleed‑through. This occurs when glue seeps through the pores of the veneer
and prevent even absorption of finishing products such as stains, and oils.
In this guide, we’ll break down why glue bleed-through happens, how it impacts
finishing, how to detect it early, and what you can do if you discover it after applying
a finish.
Veneer Characteristics
If you’re familiar with the iconic Gibson Les Paul, or Paul Reid Smith Guitars, you’ve
seen how a maple top can transform the look of a guitar.
These decorative tops are made from flame maple (tiger stripe), spalted maple, or
curly/burl maple, and are prized for their detailed grain patterns that reflect light in
interesting ways, creating a real sense of depth and texture.
For kit guitars, a veneer serves the same decorative purpose, but instead of being a
solid maple cap, like that found on the Gibson Les Paul, a veneer is a paper-thin
sheet of decorative maple glued to the surface of the body. Veneers used in guitar
kits are typically quite thin, measuring only around 0.6 mm (1⁄42 inch).
To apply the veneer in the factory, glue is spread on the guitar’s top or the back of the
veneer (or both), and pressure is applied. This process ensures good contact and
even adhesion, but because the veneer is so thin, it increases the risk of glue
bleeding through to the surface.
Why Glue Bleed-Through Affects Finishes
When finishing a guitar with a decorative veneer, it’s common practice to use a
semi-transparent finish e.g. a stain so that the decorative grain pattern is seen, and in
many cases, accentuated with color.
If, however, glue has bled through the veneer, the glue seals the wood, preventing
even absorption, resulting in a blotchy finish.
And to complicate things further, glue is not always visible on unfinished wood. It
may appear shiny or occasionally slightly darker, but to the untrained eye it often
only shows up after the first coat of stain.
That’s why early detection is essential.
Detecting Glue Bleed Through on Veneer
Below are two methods you can use to reveal glue on the surface of the veneer.
1. Wiping the veneer with mineral spirits or alcohol
Lightly wiping unfinished veneer with denatured alcohol or mineral spirits darkens
the veneer surface, making glue on the surface stand out. Areas where glue has bled
through the veneer typically remain lighter, glossier and more reflective than the
surrounding wood. You can also use a thin mist of water applied from a spray bottle,
but denatured alcohol or mineral spirits evaporate quickly and won’t swell the
veneer.
2. Sand and visually inspect
While option 1 is more reliable, you can also detect glue on the surface of your guitar
by gently sanding the surface. As you sand, areas of glue will often appear shinier
than the surrounding wood. Keep in mind, the veneer is very thin, so avoid
particularly coarse sandpaper.
Removing Glue Before Finishing
If either of the 2 methods above reveal glue on the surface of the veneer, it must be
removed prior to applying absorptive finishing products. While the options below
can be a little hit-and-miss if the glue has bled through from the body, there are 2
methods I recommend:
Scraping: A sharp scraping tool or razor blade used on a low angle can shave off dried glue without removing excess wood. It should be noted however, that scraping is often only useful for surface-level contamination e.g. where glue has dried on top of the wood, it does little for deeper contamination.
Sanding: As already discussed, but bears mentioning again, keep in mind how
thin veneer typically is, and avoid coarse grits if attempting to remove glue by
sanding. Instead, use 320-400-grit sandpaper by hand (never use a sanding
tool) or try using fine grade steel wool, and check your work frequently. The
goal here isn’t to “cut away” glue but, instead to abrade the surface. This can
be useful for light glue contamination, but if there’s a large amount of glue,
sanding is also unlikely to solve it, and at that point you may need to consider
your finishing strategy.
Why Not Use a Solvent?
Once glue has penetrated the veneer, solvents usually won’t help. While they might
soften surface glue, allowing for easier surface level removal, they won’t dissolve
cured glue.
The other issue with using a solvent is even mild solvents like vinegar, may react with
the wood, resulting in discolouration. This will be especially noticeable on pale,
figured maple veneers.
What to Do If Glue Bleed-Through Has Already Occurred
While you can certainly try the methods we’ve touched on above, unfortunately,
once glue has soaked into the wood fibres, there’s no fail safe way to remove it in my
experience, without damaging the veneer surface.
Because the glue seals the wood at a cellular level, as explained above, sanding,
scraping, or solvents can only do so much. However, there are alternatives, but these depend on how visible the contamination is, how far along you are in the process, and how open you are to changing your approach.
1. If the glue is light and you haven’t begun the finishing process:
Consider applying a pre-stain conditioner. While it won’t solve the issue
completely, it can reduce the contrast between sealed (glue affected) and
unsealed areas and help the stain absorb more evenly. Ideally, if applying this
method, test your stain on a scrap piece of wood (ideally a scrap piece of
veneer) to check how visible the problem is before applying to the guitar.
2. If the glue is deep or the stain is already blotchy:
Consider switching to coloring the guitar with tinted clear coats over sealed
wood, rather than relying on stain being absorbed into the wood. For example,
spray a tinted poly, acrylic or nitro lacquer to introduce color. Unlike stain, the
color sits on top and absorption isn’t prevented by the glue since the wood is
sealed.
Image courtesy of builder Mike Rego
If the problem is concentrated in a small area on the edge of the body, a burst
finish e.g. applying a darker edge is arguably your best option, as it can hide
the impact, but it largely depends on the location of the glue affected area.
Summing Things up
Glue bleed-through is one of those frustrating finishing problems that’s considerably
easier to prevent than repair. Once glue has bled-through, your options become
more about containing the problem rather than eliminating it, or changing your
finishing approach.
Careful inspection before finishing is therefore critical.
Lastly, while already mentioned several times, avoid heavy sanding. In the majority of
cases, those new to building kit guitars will ultimately sand through the veneer, in
which case the only viable solution is to completely remove it.
Meet the author
