The Bubble Veneer Problem , How to Fix it

Bubble veneer, lifting veneer, or loose veneer is a problem when the veneer layer is bubbling or lifting at the veneer panel. The problem that is often encountered in the woodworking manufacturer's factory. Bubble veneer happens when the wood veneer does not stick properly to its core. The bubble veneer can appear very much and become a big problem to the veneer surface. The veneer bubble will be more visible if the wood veneer is finished. The bubble part will be cut off when it is sanded and seem as white wood. The bubble is more obvious when the veneer is laid on the flat and big panel, especially when the high gloss finish is generated. But even for the low sheen finished, the bubble is still a problem; consider it a defect for the product result. 

Here are some tips to avoid the bubble veneer.

• Use good-quality glue.

Glue is a substance that attaches the veneer to its core; the quality of bonding depends on the quality of the glue and also its compatibility. Make sure that the glues used work well with the substrate and machine specification. Choose the good-quality glue to attach the veneer to the cores. We may do some testing to find the glue with the best results. Do a proper mixing and stirring to mix glue according to the instructions that are recommended by the supplier. Check the condition of glue physically; make sure he's still in good condition. The glue to the veneering is usually a two-component type which must be mixed in the proper way before it used

• The proper application.

There are many types of glue that may require different applications. The veneering process is usually done by a hot press machine, since the glue used must be type that can be dried quickly with the heating process. Make sure we fulfill the conditions needed, such as the temperature of the press, the drying time, the pressure, the thickness of the glue layer, etc. 

Prepare the surface properly; blow and clean the veneer and core from any dirt. The solid particles, chemicals, or oils will interfere with the attachment of the glue.

• The moisture content of veneer and the core

Most of the wood adhesives are water-based. The water in the glue will wet the surface of the core and veneer before it evaporates to leave a dry and strong bond. The veneer sheet is usually dry when we purchase it; if we use MDF, particle, or plywood, then they are also marketed in the dry condition. But the weather at the time of the veneering process may raise the moisture content. Then make sure we always check the moisture content of the cores and the veneer when we do veneering. If we use the laminated board as the core, then a proper sanding is also needed to make sure that the core surface is even.

• Recognize the type of wood veneer

The veneer is a natural product that has a variety of properties and characters. Some types of wood may require special treatment. For example, the rosewood veneer contains some oil that may interfere with the gluing process. Clean the oil with acetone to minimize the oil from the veneer before it is glued. Some other veneer, such as burl or crotch, is tough and brittle, which makes the veneering rather difficult. We may need to use some special chemical to soften the brittle and tough veneer. You can find more information in our previous article: Veneer conditioner

How to fix the bubbled veneer panel

Although the bubble is caused by an improper gluing process, the bubble problem is often found in the finishing process. The bubble veneer is appearing when the veneer surface has been coated with finishing materials. Sometimes bubbles may be visible on the stain application, but often the bubble appears at the sealer application. And in this state, the process of repairing will always damage the existing finishing layer. 

To fix this problem, the bubble needs to be opened and reglued. Clean and wash the finished off if the surface is already finished. Then cut the bubbled veneer with a thin and sharp knife, then put glue into the opened veneer and then press and heat it to make the glue dry. You can use the hot iron to press and heat the veneer and dry the glue. After the glue is dry, it needs to be resanded to get an even, smooth surface. This process needs to be done carefully by skilled craftsmen. In some cases, you can get the problem fixed, but in a bad case, the whole bad veneer needs to be removed and re veneered. 

After the veneer corrects, it must be followed by the refinishing process.