Coloring wood veneer

Excerpt: Veneer is a thin slice of wood peeled from a timber log and having predetermined thickness usually less than 3 mm or 1/8th of an inch but can slightly vary depending on the end use application.

Introduction

Fashion is ever changing and evolving along with the techno-economic and cultural growth of the human race. It is not limited only to the personal garb, accessory wear, jewelry, make-up or hair-style but also encompasses the surrounding ambiance and the living conditions. In this regard, the fashion trend in furniture used for home décor, hotel and workplace area is rapidly growing.

Wood is the most common and popular material used in decorative furniture. However, with the indiscriminate destruction of trees and depleting forests, availability of a specific quality of wood required for durable furniture making is declining and becoming quite expensive. Therefore, instead of using solid wood from the stem or bark of a tree, only a thin layer of wood is cut and then pasted on the exterior part of other suitable material to impart a natural and fashionably vintage look to the furniture.

Wood Veneer

Veneer is a thin slice of wood peeled from a timber log and having predetermined thickness usually less than 3 mm or 1/8th of an inch but can slightly vary depending on the end use application. Nowadays it is widely used in making plywood and laminations for decorative and architectural purposes. Veneer making process has gained importance and prominence owing to the increasing shortage of available timber as well as reducing ecological concerns. Use of veneer in decorative articles helps furniture manufacturers in accomplishing designs that would be difficult or very expensive to create with solid wood.

Wood from about 200 types of trees is considered suitable for the veneer making. The commonly preferred trees are Teak, Oak, Walnut, Maple, Cherry, Ebony, Mahogany and Bamboo. Further, depending on the methods used for wood cutting and peeling, the color, pattern and visual effect would vary. Two logs of the same species, but with their veneers cut differently, will have entirely different surface characteristics.

Generally, there are three major methods of veneer cutting, viz. rotary peeling, slicing (quarter cut| crown cut| rift cut) and half-round slicing. These methods produce different grain patterns regardless of the wood species involved. A few examples of wood species are shown in Figure 1.

Classifications of Veneers

  1. Constructional - used mainly for the production of plywood which consists of an odd number of laminations of veneer bonded at right angles to each other to enhance engineering properties and for Laminated Veneer Lumber (LVL) which is made up of parallel veneer laminations, glued and processed together to form a timber material.

  2. Decorative – to enhance the aesthetic surface appeal. These are generally used in the decorative and architectural furniture making such as cabinets, profile-wrapped moldings and paneling.

Usage of Veneer

There are many end-use application of veneers and the list is continuously increasing based on furniture and architectural designer's creative imagination. Some popular areas include:

  • Furniture fitting and lining
  • Cabinet making
  • Floor and wall laminating
  • Boat interior
  • Vehicle interior
  • Landscaping
  • Architectural decoration
  • Constructional material

In woodworking, veneers are glued onto core panels (typically, wood, particle board or medium-density fiberboard) to produce flat panels such as doors, tops, and panels for cabinets, parquet floors and parts of furniture. The construction of plywood and flow-chart of the manufacturing process are presented in Figure 2 and Figure 3 respectively.

Coloration of Veneer

Color is a vital parameter for enhancing the aesthetic and decorative value of wood veneers used in interior applications, such as furniture, joinery, paneling and architectural products. Many hardwood species have non-homogeneous natural colors and mostly do not meet the requirements | expectations of consumers. The color disharmony can be overcome by making use of different techniques, such as staining, coating and dyeing.

Keeping in mind the ever-changing challenges faced by the veneer processors, Atul Colors has developed an innovative and unique range of TULAVAN VC dyes. The salient features and benefits of coloration with these dyes are:

  • ensure adequate dye diffusion inside the wood core
  • achieve shade
  • tone as per the designer's needs
  • enhance aesthetic appeal
  • avoid color bleeding in water
  • prevent discoloration when wiped with home cleaners

Commercial dyeing of veneer is a specialized method and needs optimum control over process parameters. Atul Colors has devised and established a simple and easy to apply the dyeing process. Depending on the requirement of shade, depth and brightness of color, a pre-treatment process is incorporated before coloration. The Guideline processes are furnished below for reference purpose:

Pre-treatment

Dyeing

Before the start of dyeing, the pre-treated veneer substrate is soaked in acidic water (pH: 4.0-4.5, maintained using Acetic acid) at room temperature for 60-90 minutes with occasional liquor bath agitation. Then the dyestuff is dissolved in acidic water (pH: 4.0-4.5) and the dyeing is initiated. The schematic guideline dyeing process is presented in Figure 4.

Development of popular shades

Some commonly used veneers and popularly dyed color combinations are illustrated in Figure 5.

Summary

With the rapid development in furniture and interior decoration industry, demand for wood veneer is increasing exponentially. The manufacturing of veneer-based products has been identified as an unprecedented opportunity to promote higher value utilization of plantation resources. Coloration substantially raises the aesthetic value of veneers and TULAVAN VC range of specialty dyes offer the tailor-made solution to satisfy the needs of customers.

References

  1. A Manual for Decorative Wood Veneering Technology; 2nd Edition; Project No: PRA295-1213; Forest & Wood Products, Australia; July, 2013
  2. tabu: Pre-dyed Veneers catalogue
  3. N Nguyen, B Ozarska, M Fergusson and P Vinden; Investigation into the Optimal Dyeing Method for Bluegum (Eucalyptus globulus) Veneer; Bio Resources; 13 (3); 6444-6464
  4. W U Yiqiang and P Wanxi; Study on the Optimised Dyeing Technology of Wood Veneer based on Reducing Discharge of Wastewater; www.seidatacollection.com

Author Details

Dr Ashok Athalye and Arindam Chakraborty

Technical Service, Atul Ltd (Colors Business), Valsad, Gujarat, India