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) or less.
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.
Got Glue Bleed-Through? How You Can Tell
Ideally, issues with glue bleed-through are noticed upon initial inspection of the guitar body (more on how to do this below), but if you’ve already started applying a finish and notice uneven colour uptake, you must confirm the problem before trying any of the methods suggested below.
Remember, not all surface blotches are caused by glue bleed-through, and misdiagnosing the issue could potentially make things worse.
Below are the most common causes, and how to tell which is affecting your guitar.
Glue Bleed-Through
Glue bleed-through has a few tell-tale signs once a finish is being applied:
Image courtesy of builder Mike Rego
- Hard, defined edges: Glue-affected areas of the veneer tend to have relatively sharp edges. The transition from coloured to uncoloured veneer will almost look deliberate, as if it’s been masked off.
- Shiny, or reflective quality: Under angled light, especially, glue spots often appear glossier/shinier than the surrounding veneer, even after sanding.
- Pattern follows pressure/glue spread zones: The shapes created by glue bleed-through aren’t usually the same as random grain features or contaminants in the finish. As they are most likely caused when the glue was pressed through the veneer during factory lamination, you will tend to notice them more near routed areas and/or where pressure and squeeze-out are highest.
Oil Saturation or Uneven Application
Uneven colour can also be caused by oil or finish pooling in certain areas. This is usually much easier to address. Here’s how you can check:
- Soft, feathered edges: Unlike glue, oil-related blotching usually fades gradually into the surrounding area rather than stopping abruptly.
- Darkened patches: These areas often appear darker, not lighter, due to increased absorption.
Sanding Issues
Over-sanding the veneer can also affect finish absorption:
- Dull appearance: Heavily sanded areas (or if you have partially sanded through the veneer) may absorb less finish, like glue bleed-through, but usually lack the shiny, hard-edged look of glue.
- Follows sanding patterns: The affected areas often align with sanding strokes or edges rather than appearing near routed areas or seams in the veneer where glue is most likely to be found.
Veneer Compression
Uneven finish absorption may also be blamed on veneer compression, which can occur during pressing. While the compression of surface fibres can reduce stain uptake, the tell-tale signs of compression tend to be soft, gradual transitions, and can usually be improved with careful, light sanding.
As noted above, glue bleed-through creates hard-edged, persistent light patches that do not improve with additional sanding or finish.
In practice, sharp-edged, clearly defined areas of complete stain rejection, particularly near cavities or edges of the body, are almost always caused by glue, not compression.
Why Identifying the Cause Matters
If the problem is glue bleed-through, continuing to sand will increase your risk of sanding through the veneer, and when this happens the best course of action in many circumstances is to remove the veneer altogether.
If the issue is caused by oil or finish saturation, you can usually fix the problem by wiping back, light sanding, or allowing the finish to cure and even out. In either scenario, correctly identifying the cause first will potentially save both the veneer and the finish.
Detecting Glue Bleed Through on Veneer
Ideally, if there is an issue with glue-bleed-through, you will notice it upon initial inspection. 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.
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.
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