By David Nicholls, USDA Forest Service, PNW Research Station, Sitka Wood Utilization Station (Sitka, AK); Matthew Bumgardner, USDA Forest Service, Northern Research Station (Delaware, OH); and Valerie Barber, University of Alaska-Fairbanks, Forest Products Program


   
Figure 1. Red alder edge-glue panel
(high level of character-marked wood).
Figure 2. Paper birch edge-glue panel
(high level of natural stain). 


Edge-glued panels can be manufactured for a variety of end uses such as furniture and kitchen cabinets, or as standard-sized blanks. The production of edge-glued panels maximizes resources by using lower grades or character-marked lumber, including paper birch and red alder lumber. Both paper birch and red alder are small diameter hardwoods, with rotation ages typically about 80 years or less in the United States. Thus, much of this resource has high levels of knots and other character mark features.

A recent research study conducted by the USDA Forest Service looked at the advantages of edge-glued panel production, including the relatively low cost of equipment, the potential use of smaller diameter stems and/or lower grades of lumber, the flexibility in panel sizes and opportunities to sell within established local markets.

 
Figure 3. General interest in character-marked wood
products by wood products manufacturers.

 
Figure 4. Past use of red alder and paper birch by
wood products manufacturers (percent of respondents
indicating past use).

Kiln-dried, planed birch lumber from interior Alaska, and red alder harvested from southeast Alaska, were the source materials for constructing edge-glued panels in this research study. The objectives included:
1. Assessing the overall interest in edge-glued panels by wood products manufacturers.

2. Evaluate panels constructed from two different species: paper birch and red alder.

3. Evaluating birch panels having two different character features: knots and natural stain.

4. Evaluating birch and red alder panels at three different character mark frequency levels, ranging from light to heavy.

Survey Overview
We asked the 129 respondents to evaluate 11 edge-glued panel samples presented side by side in a display booth. They evaluated the panels on a 5-point scale, based on three attributes: character marks, grain consistency and overall color. Respondents also selected their three overall favorite panels. They then rated their preferences for two different groups of panels: red alder vs. birch and birch knots vs. birch stain. All data was collected in cooperation with the University of Alaska-Fairbanks wood products program.

Most respondents were male (89%) and 43% were at least 51 years of age. Most represented small firms; 42% had annual sales of less than $250,000; 60% were $1 million or less; and 71% had 10 or fewer employees.

All panels were constructed to a finished size of 12 by 18 inches, with each strip being about 1 to 2 inches wide. All lumber was kiln-dried and planed, followed by application of a clear coat finish. No other stains or finishes were applied so that the original color and texture of the panels could be preserved.

For red alder, one panel was constructed from clear wood, and three panels were constructed from varying levels of knots (Table 1). For birch, one panel was constructed from clear wood, three panels from varying levels of knots, and three panels from varying levels of natural stain (Table 1). The study included a total of four red alder panels and seven birch panels.

Table 1. Edge-glued panel descriptions and popularity among
wood products producers.

Table 2. Overall preferences for red alder vs. paper birch edge
-glued panels by wood products manufacturers


Survey Results

• Birch panels: Among wood products producers, birch with high levels of natural stain (Figure 2) was preferred by a wide margin, being selected 39% of the time (Table 1, panel 11). Panels from the birch stain group were considerably more popular than those from the birch knot group. Among wood products producers, 82% of respondents favored birch natural stain over birch panels with knots (Table 2).
• Red alder panels: Highly character-marked red alder (Figure 1, panel 4) was the most popular red alder panel among wood products producers, being chosen as favorite nearly 14% of the time (Table 1). The clear red alder panel (panel 1) was selected as the favorite about 10% of the time. The red alder panels having intermediate levels of character (panels 2 and 3) were rarely selected as the favorite.
• Red alder vs. birch panels: In general, birch panels were more popular than red alder among wood products producers (Table 2), with birch panels being preferred about 57% of the time.
• Character-mark interest: Wood products producers indicated only a moderate general interest in using character-marked wood in their products (Figure 3), with 45% of respondents indicating a high or very high interest in character-marked wood.
• Past use of hardwood species: Wood products producers indicated a relatively high past usage of red alder, with over 61% of respondents indicating some past use of this species (Figure 4). Birch was also widely used among wood products producers, with almost 74% of respondents indicating some past use.

Conclusions
This study found that wood products producers had strong preferences for birch panels featuring high levels of natural stain, and to a lesser degree birch panels having moderate levels of stain. Birch panels containing stain were greatly preferred to birch panels containing knots, suggesting this type of character-mark generally has greater appeal.

Some respondents mentioned that the overall appearance of the birch stained panels was similar to the distinctive striped look of hickory. This could suggest advantages for products to imitate more popular or more expensive products. When considering red alder panels, clear wood and heavy character was generally preferred to moderately character-marked wood (Table 1). This finding would suggest that manufacturers could benefit from lumber sorting strategies where clear wood and high character wood are separated from intermediate grades to take advantage of this “U-shaped” preference structure.

The study also found that small wood products producers might be open to using highly stained birch in edge-glued panels. One advantage to being small and using character-marked wood is that manufacturers can work directly with customers, ahead of actual production, to determine exactly which character pieces will go into the panels. In this way, manufacturers can have more confidence in using the heavily character-marked wood that might appeal to some consumers more than others. Character-marked wood, prevalent in Alaska and elsewhere, thus has potential to become a source of customized production, leading to opportunities for product differentiation.

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