A common issue which occurs in wood veneer for furniture is the onset of miniature cracks inside its finish, which is referred to as checks or checking. They usually manifest themselves in the form of hairline cracks which are uniformly spaced out, and in extreme cases they might be accompanied by ridges within the wooden surfaces. Below are some tips for getting rid of checks while minimizing their occurrence.
Where Do Veneer Checks Come From?
Veneer checks result from stress failures that appear within the facial veneer. Swelling or differential shrinkage occurs within the panel substrate or face. When environmental humidity changes, moisture content within the panel will change with it. For wood, moisture content changes often involve swelling or shrinkage. However, when veneer panels swell or shrink, its veneer doesn’t always shift in the same manner as its substrate. This produces substantial panel stress which can lead to wood failure.
The failure will typically manifest itself within the wood’s weakest portion, which is either large pores or deeper lathe cracks. Once the face veneer fails, this will generate stress concentrations within your finish which will showcase the visible cracks that are referred to as checks.
How to Repair Veneer Checks
Epoxy which is either silica thickened or straight has proven very useful in repairing checks, especially in plywood. The reason is because epoxy has both sealant and adhesive attributes which are greater than paint. When placed on bare wood, it will stabilize its grain while providing a barrier which protects it against moisture intrusion.
Furthermore, it serves as a dependable base for additional applications involving primer, varnish or paint. If you’re working with a surface that is quite rough, fairing compound is a great way to smoothen it. For example, when working with okoume based plywood, many experts recommend using dual epoxy coats for sealing its veneer grain prior to adding fairing compound for smoothening. This will get rid of any irregularities, and then polyurethane paint with primer can be added if desired.
How to Prevent Veneer Checks
A quality coat is the key to slowing down moisture exchange, because it will minimize the adverse effects of contraction or expansion. Additionally, you will also want to consider strength versus stress. If the adhesive and veneer strength is higher than stress coming from the altering moisture content, this means checking won’t occur. However, in most cases, should the moisture content obtain an extreme low or high, its stress will overwhelm the adhesive and veneer strength, which will result in failure.
Because wood comes from nature, it has certain attributes which are beyond the control of humans. To prevent problems with checking, you must first understand the properties and plan your projects accordingly.
For example, prior to initiating a project involving engineered or natural wood, be sure every component has been seasoned together with moisture content which closely mimics the environment you plan to keep it in. Once the project has been completed with moisture content that is suitable, it must stay within a reasonable range, and you should avoid exposing it to drastically varying humidity levels.