" " wisno wood furniture finishing: The bubble problem in the veneer

Thursday, February 16, 2012

The bubble problem in the veneer


Bubble veneer, lifting veneer, or loose veneer is the problem that is often encountered in the veneering process.  It is caused by the wood veneer that does not stick properly to its core. The Bubble veneer can appear very much and become 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 at the flat and big panel especially when the high gloss finish is generated. But even for the low sheen finished, the bubble is still be problem,
Although the bubble is caused by improper gluing process, but 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 bubble 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. The action to fix the bubble must be followed by the process of washing off the finishing layer and the re finishing process. It can be considered as wasting of finishing material and time. Then it will be much better if we can do the right veneering process to minimize the bubble problem.
 

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 is determined by the quality of glue. Choose the good quality and proper glue to attache 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 of that is recommended by the supplier. Check the condition of glue physically; make sure he's still in good condition. The glue to the veneering usually is a two components type which must be mixed in the proper mixed before it used.
  • The proper application.
There are many types of glue that may require different application. The veneering process is usually done by hot press machine, since that the glue used must be type that can be dry quickly with the heating process. Make sure we are fulfill the condition needed such as: 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 form any dirt. The solid particles, chemicals or oils will interfere with attachment of the glue.
  • The moisture content of veneer and the core
Most of the wood adhesive 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 bonding. The veneer sheet is usually has dry when we purchased, if we use mdf, particle or plywood then they are also marketed in the dry condition.  But the weather in the time of veneering process may raise the moisture content. Then make sure we to 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 used.
The veneer is the wood product that has variety properties and character. Some types of wood may require special treatment. For example the rosewood veneer contains some oil that may interfere the gluing process. Clean the oil with acetone to minimize the oil form the rosewood veneer. (rosewood veneer for furniture) Some other veneer such as: burl or crotch is tough and brittle that make the veneering is rather difficult. We may need to use some special chemical to soften the brittle and tough veneer. ( walnut burl veneer)

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