How To Fix Blistered Wood Veneer
Blistered Veneer: Causes and Repair Methods
The image above shows how older veneered mahogany can sometimes lift away from the surface, creating ridged blisters. These blisters are caused by small amounts of liquid seeping through tiny tears or splits in the veneer. Early signs of this issue can be seen on the left-hand side of the picture.
Over time, water ingress (and furniture spray polish 😳) causes the veneer to swell, pushing it up into linear ridges. If you're lucky, tapping on the ridges will produce a hollow sound, indicating they're repairable. However, if the ridges feel solid or don't sound hollow, it may mean the substrate underneath has also swollen, making repairs much more challenging and in some cases beyond repair.
How to Fix Blistered Veneer
First Method: Heat and Pressure
For hollow-sounding blisters, try this simple approach:
- Using an old iron, apply it directly to the surface of the blister. Place a barrier, like greaseproof paper, between the iron and the veneer to prevent scorching.
- As the heat flattens the blister, quickly press a flat, heavy, cold metal weight onto the area. This helps the glue beneath re-cure as it cools.
- Keep moving the weight to absorb residual heat while holding the veneer flat.
This method works because older furniture typically used water-based animal glue, which softens when heated and re-bonds when cooled.
Second Method: Injecting Glue
If heating doesn't work, or for stubborn blisters, try this:
- Carefully use a scalpel or craft knife to lift or create a small slit in the blister.
- Apply glue into the cavity using a cocktail stick or another improvised tool, ensuring minimal further damage.
- If the veneer has swollen and can't lay flat, you may need to trim a tiny amount from the edges before gluing it down.
Third Method: Substrate Repair
For severe blisters caused by swelling of the substrate beneath the veneer:
- Carefully cut away the blistered veneer but don't discard the pieces—you may be able to reuse them.
- Using a sharp chisel, remove the swollen substrate, taking care not to dig too deep. If necessary, fill the void with wood filler to level the surface.
- Reattach the original veneer pieces if possible. They may need slight shaping to fit, but they'll match better than new veneer.
If reusing the veneer isn't feasible, replace it with a new piece that closely matches the original in color and grain. To disguise the repair:
- Cut the replacement veneer into an oval shape, slightly larger than the repair area.
- Trace around the patch and cut away the damaged area to create a snug fit for the new piece.
- Patience and precision are key here.
Repairs are best done before stripping and refinishing furniture, as the stripping process helps blend the repair into the piece's natural patina, maintaining its character and history.
Choosing the Right Glue
Superglue (with Activator)
Advantages: Fast and strong. Ideal for quick fixes.
Caution: Apply sparingly—there's no room for mistakes. Always test the fit of the repair before applying glue.
Apply glue to the repair area, massage it in, and spray activator. Quickly press the veneer flat with a heavy object, keeping it in motion until the glue sets.
White PVA Wood Glue
Advantages: Versatile, dries clear, and allows time for adjustments.
Caution: Requires weighting to hold the veneer flat while drying, which can take hours. Use greaseproof paper as a barrier and clean excess glue before weighting.
Loctite Hide Wood Glue
Advantages: Reversible with heat, making it ideal for historically significant pieces.
Drawback: Longer drying time compared to PVA glue.
Traditional Hot Melt Hide Glue (Pearl Glue)
Advantages: The gold standard for antique restoration. This animal-based glue is incredibly versatile and entirely reversible.
Caution: Requires soaking and heating, making it less practical for non-professionals. It also has a distinctive smell when heated!
In Gilboys Workshop
In an old drinking mug rests a large 50ml syringe, loaded with pearl glue, ready to be used at any time. When needed, we boil a kettle and pour the boiling water into the mug. This softens and liquefies the glue in the syringe, making it ready for use.
Injecting hot pearl glue under loose or blistered veneer is our most common method of repair in the workshop. It takes some care and dexterity to avoid over-injecting, though this can still happen. We always keep a hot, damp cloth nearby to quickly wipe away any excess glue. This is the most effective and proper way to repair blisters on period antique furniture. We also have a variety of antique weights that we use to weigh down the veneer after gluing. If access allows, we use clamps with protective wood pieces to force the veneer flat.
If you’ve successfully repaired your veneer and don’t plan on stripping the finish, applying a beeswax polish will help blend the repair while preserving and protecting the finish. We almost always use beeswax polish as the final touch in our restoration work. It provides a lovely protective, natural sheen and visually enhances the piece, giving it a perfect finish that reflects the care given to a well-preserved antique.
If you’re applying beeswax polish to your piece of furniture, avoid focusing on the repaired areas. Instead, apply the wax to the entire piece as if the repairs weren’t there. This will ensure an even application and prevent highlighting any imperfections in your work. Beeswax polishing contributes to the patina, helping to create that lovely, natural feel we all love in antique furniture. I created our beeswax polish specifically to be used on tired old shellac finishes, where it works its best. Rich in natural waxes, it acts like a skin cream—nourishing dry areas and reviving the old finish.
