United States 

Department of 

Agriculture Photographic Guide of Selected 

Forest Service External Defect Indicators and 

Northeastern Forest 

Experiment Station Associated Internal Defects 

Research Paper NE-647 in Sugar Maple 

Everette D. Rast 

John A. Beaton 

David L. Sonderman 
Abstract 

To properly classify or grade logs or trees, one must be able to correctly identify 

indicators and assess the effect of the underlying defect on possible end products. 

This guide assists the individual in identifying the surface defect indicator and 

shows the progressive stages of the defect throughout its development for sugar 

maple. Eleven types of external defect indicators and associated defects that are 

particularly difficult to evaluate are illustrated and described. 

The Authors 

EVERETTE D. RAST, forest products technologist, received a B.S. degree in 

forestry from the University of Missouri in 1960 and an M.S. degree in agricultural 

economics from The Ohio State University in 1970. He joined the USDA Forest 

Service in 1960 as a forester on the Mendocino National Forest and transferred to 

the Northeastern Forest Experiment Station, Delaware, Ohio, in 1966. From 1966 

to 1987 he was with the log and tree grade project, and then the management and 

utilization alternatives for nonindustrial private forests. In 1987 he was transferred 

to the Station's Forestry Sciences Laboratory in Princeton, West Virginia, as a 

member of the Advanced Hardwood Processing and Technical Resource Center. 

JOHN A. BEATON, forestry technician, received a certificate as a forest technician 

from Lake City Junior College and Forest Ranger School, Lake City, Florida, in 

1964. He joined the Forest Service in October 1964 as a forestry aid at the Forest 

Insect and Disease Laboratory, Delaware, Ohio. In November 1976, he was 

transferred to Project 1351, Northeastern Forest Experiment Station, Delaware, 

Ohio, as a forestry technician. 

DAVID L. SONDERMAN, forest products technologist, joined the Northeastern 

Forest Experiment Station in 1962 and was on the staff of the Eastern Softwood 

Timber Quality project until 1972. From 1972 to 1987 he was located at Delaware, 

Ohio, with the Northeastern Station's project on management and utilization 

alternatives for nonindustrial private forests. He is currently with the Station's 

Forestry Sciences Laboratory at Princeton, West Virginia. 

Manuscript received for publication 6 November 1989 

Northeastern Forest Experiment Station 

5 Radnor Corporate Center 

100 Matsonford Road, Suite 200 

P.O. Box 6775 

Radnor, Pennsylvania 19087 

May 1991 
Introduction Discussion of Defects 

This photographic guide on sugar maple is the sixth in a series 

designed to assist in the understanding of the relationship 

between exterior defect indicators and the underlying defect. 

In this study, like the previous studies on black walnut (Rast 

et al. 1988), white oak (Rast et al. 1989), and yellow-poplar 

(Rast et al. 1990), bolts were sliced and photographs of the 

interior defects were taken at the USDA Forest Service's 

Forest Products Laboratory in Madison, Wisconsin. In this 

publication we provide a stereo pair of photographs of the 

defect indicators to give the user a more realistic view. 

Procedure 

Thirteen sugar maple trees on the Florence Hanger District 

of the Nicolet National Forest in northeastern Wisconsin 

were selected, felled, and bucked into twenty five 4-foot 

bolts containing the defects to be studied. Many of the bolts 

contained two or more defects. The bolts were carefully 

transported to a warehouse to be photographed. This 

controlled environment enabled us to take quality 

photographs of defect indicators and provided a good 

storage area for the bolts until the film was developed and 

the photos checked. 

The ends of the bolts were marked off in quadrants using 

the geometric center as the midpoint. The quadrants were 

aligned to keep all the defects in quadrant 1 or 2, if 

possible. A 1-inch groove was routed along the 3-4 quadrant 

line, providing an identification mark in the rotary-cut veneer 

for clipping. By clipping at this point, each sheet of veneer 

was one complete revolution of the log. This provided a 

method for identifying the correct defects corresponding to 

the surface defect indicators that were photographed. 

Prior to slicing, the bolts were steam-heated in a water vat 

just enough to loosen the bark. Next, the bolts were 

debarked by hand, replaced in the vats, and heated to the 

correct slicing temperature. A bolt was then removed from 

the vat, chucked in the lathe, and rotarysliced into 

1110-inch-thick veneer. Before getting a continuous sheet of 

veneer, the round-up pieces of veneer were counted and 

those necessary for photographing were saved. Once it 

began coming off in a continuous sheet, the veneer was 

clipped at the notch in the small end and stacked by bolts. 

The bolt number was put on the first and last sheet of 

veneer to identify each bolt. Only 10 to 15 bolts were sliced 

at a time so the defects could be photographed the same 

day to prevent stain or discoloration. Then the veneer was 

put in cold storage before drying. 

The defect indicators reported in this publication are: 

suppressed bud; suppressed bud cluster; open and 

occluded (closed) bird peck; light, medium, and heavy bark 

distortions; new and old wounds; surface rise; and burl. We 

believe that these indicators often are difficult to identify 

and evaluate in terms of their effect on end-product quality. 

Graders normally have little difficulty recognizing and 

evaluating the obvious grading defects such as limbs, forks, 

bumps, and butt scars. 

The photo format for each defect evaluated in this 

publication is, first, a pair of stereo photographs of the 

defect indicator on the log surface. Next is an enlarged set 

of prints showing the defect indicator followed by a series of 

prints of the actual defect as it appears at different depths 

below the log surface. Below the photo of the defect 

indicator (Fig. 1) is a list that describes the size of the defect 

in terms of length (along the grain), width (across the grain), 

and height (above the normal bark contour); log diameter, 

inside the bark (ib) at the defect; round-up thickness; core 

diameter; and distance of defect above the stump. The 

information listed below the interior defect (Fig. 1) indicates 

distance below the log surface (inside the bark) as well as 

the distance from the first slice of veneer to that particular 

photographed defect. The last photograph in each defect 

series also lists total veneer thickness, which is the distance 

from the initial slice of usable veneer to the veneer core. 

Suppressed Buds 

Epicormic branches develop from two types of buds: 

suppressed or dormant buds and adventitious buds 

(Kormanik and Brown 1969 and Shigo 1986). Suppressed 

buds (Figs. 1 and 2) can persist for many years as a bud 

trace or they can sprout suddenly after some stimulus such 

as thinning or damage to the tree. After sprouting, many 

develop into small limbs that often die. In contrast, bud 

traces usually continue to form in the cambial zone even 

after the epicormic limb dies and eventually drops off (Fig. 

I), sometimes forming another epicormic limb which may or 

may not develop. Occasionally the suppressed bud may 

cease all activity in the cambial zone following its 

occurrence, showing no evidence of the bud trace (Fig. 2). 

By contrast, adventitious buds form anew from the 

cambium, usually following injury to the tree. The defect 

indicator for both bud types is identified by a slight break in 

the bark pattern with a small protuberance in the center. 
Figure 1 .-Suppressed bud and associated internal defects. 

Stereo view of defect indicator 

Defect size .......................... 1/2 x 1/2 inches Depth belowLog diameter at defect (ib) .............. 22.1 inches 

Round-up thickness ................... 0.5 inch Logsurface ................................ 0.5inch 

Core diameter. ....................... 5.7 inches First sheet of veneer ........................ 0.0 inch 

Defect distance above stump. ........... 5.5 feet 
Figure 1 (Continued) 

Depth belowLogsurface .............................. 1.5inches 

First sheet of veneer. ...................... 1.0 inch 

Depth belowLogsurface .............................. 3.5inches 

First sheet of veneer. ...................... 3.0 inches 

Depth belowLog surface. ............................. 2.5 inches 

First sheet of veneer. ...................... 2.0 inches 

Depth belowLog surface .............................. 4.5 inches 

First sheet of veneer. ...................... 4.0 inches 
Figure 1 (Continued) 

Depth belowLogsurface .............................. 5.5inches 

First sheet of veneer. ...................... 5.0 inches 

Depth belowLogsurface .............................. 8.5inches 

First sheet of veneer. ...................... 8.0 inches 

Depth belowLog surface. ............................. 6.5 inches 

First sheet of veneer. ...................... 6.0 inches 

Total Veneer Thickness .................... 8.0 inches 
Figure 2.-Suppressed bud and associated internal defects. 

Stereo view of defect indicator 

Defect size .......................... l/2 x I/2 inch 

Log diameter at defect (ib) .............. 16.2 inches 

Round-up thickness ................... 0.3 inch 

Core diameter ........................ 5.8 inches 

Defect distance above stump. ........... 13.5 feet 

Depth belowLogsurface .............................. 4.8inches 

First sheet of veneer. ...................... 4.5 inches 
Figure 2 (Continued) 

Depth belowLogsurface .............................. 5.3inches 

First sheet of veneer. ...................... 5.0 inches 

Total Veneer Thickness .................... 5.0 inches 
Suppressed Bud Cluster 

As its name implies, a suppressed bud cluster is a group Figure 3 shows a faint evidence of the concentric rings 

of suppressed buds (3 to 20) tightly clustered in a small around the defect indicator and the presence of several 

area, normally less than 2 by 2 inches in size. Usually, there individual buds. Also, several adventitious knots are visible 

is evidence of concentric rings around the defect indicator. in the defect photos. 

Figure 3.-Suppressed bud cluster and associated internal defects. 

Stereo view of defect indicator 

Defect size ........................ 1% x 11/2 inc 

Log diameter at defect (ib) ............ 18.1 inches 

Round-up thickness ................. 0.0 inch 

Core diameter ...................... 5.9 inches 

Defect distance above stump. ......... 5.5 feet 

Depth belowLog surface. ............................... 0.5 inch 

First sheet of veneer ........................ 0.5 inch 
Figure 3 (Continued) 

Depth belowLogsurface .............................. 2.0inches 

First sheet of veneer. ...................... 2.0 inches 

Depth belowLog surface. .............................. 6.0 inches 

First sheet of veneer. ...................... 6.0 inches 

Depth belowLog surface. ............................. 4.0 inches , First sheet of veneer. ...................... 4.0 inches 

Depth belowLog surface. ............................. 7.0 inches 

First sheet of veneer. ...................... 7.0 inches 

Total Veneer Thickness .................... 7.0 inches 
Bird Peck classification should not be used except to say that new bird 

pecks can be disregarded in grading logs and trees, 

Bird peck is evaluated by determining whether callus tissue whether or not they reach the cambium layer, so long as the 

is formed in the peck holes (Rast et al. 1973). If the peck tree is cut shortly after injury. The rationale is that the peck 

holes are open, the pecks did not reach the cambium layer defects will be removed during the initial stages of primary 

and there will be no damage. But if the peck holes are processing (debarking, slabbing, or round-up) of the log. 

closed, there will be damage to the tree. Bird pecks are 

sometimes considered as old or new. However, this Figure 4 shows primarily open bird peck that is not 

Figure 4.-Open bird peck. 

Stereo view of defect indicator 

Defect size ............................ 1 x 8 inches 

Log diameter at defect (ib). ............... 20.3 inches 

Round-up thickness. .................... 0.2 inch 

Core diameter ......................... 5.8 inches 

Defect distance above stump ............. 10.0 feet 
occluded (two next to the left arrow and one in the center of By contrast, in looking at the occluded bird peck in Figure 

the photo) and, therefore, can be disregarded. However, 5, one can observe clearly the callus material in the pecked 

careful examination of the photograph reveals several holes and the defects in the underlying wood. The accompanyoccluded bird pecks (between the two arrows). No photos of ing stain is quite normal with occluded bird peck due to the 

veneer defects were taken as the only indication of defects easy entry of moisture and pathogens. Severe bird beck can 

in the wood was these occluded bird pecks. lead to a separation of the wood along the rings. 

Figure 5.-Occluded (closed) bird peck and associated internal defects. 

Stereo view of defect indicator 

Defect size ............................ 1 x 9 inches Depth belowLog diameter at defect (ib). ............... 11.7 inches 

Round-up thickness ..................... 0.1 inch Logsurface ................................ O.6inch 

Core diameter ......................... 5.6 inches First sheet of veneer ........................ 0.5 inch 

Defect distance above stump ............. 5.0 feet 
Figure 5 (Continued) 

Depth belowLogsurface ................................ 0.9inch 

First sheet of veneer ........................ 0.8 inch 

Depth belowLogsurface .............................. 1.1 inches 

First sheet of veneer. ...................... 1.0 inches 

Depth belowLogsurface .............................. 1.3inches 

First sheet of veneer. ...................... 1.2 inches 

Depth belowLogsurface .............................. 1.8inches 

First sheet of veneer. ...................... 1.7 inches 

Total Veneer Thickness .................... 2.9 inches 

11 
Bark Distortions shows a slight amount of curvature in the surrounding bark 

plates, and the bark pattern varies only slightly from normal. 

Bark distortions usually indicate an overgrown knot, and Because of these features, light bark distortions are 

because of age they have no height measurement (flush inconspicuous and often overlooked. Medium bark , with the normal contour of the bark). They are classified as distortions (Fig. 7) show more of the concentric circles, but 

light, medium, or heavy. A light bark distortion (Fig. 6) they are broken in several areas by flat bark plates or the 

Figure 6.-Light bark distortion and associated internal defects. 

Stereo view of defect indicator 

Defect size ............................ 2 x 2 inches 

Log diameter at defect (ib) ................ 16.4 inches 

Round-up thickness. .................... 0.0 inch 

Core diameter ......................... 6.2 inches 

Defect distance above stump ............. 7.0 feet 

Depth belowLogsurface .............................. 4.0inches 

First sheet of veneer. ...................... 4.0 inches 
Figure 6 (Continued) 

Depth below- Depth belowLog surface. ............................. 4.5 inches Log surface. ............................. 5.1 inches 

First sheet of veneer. ...................... 4.5 inches First sheet of veneer. ...................... 5.1 inches 

Total Veneer Thickness .................... 5.1 inches 
Figure 7.-Medium bark distortion and associated internal defects. 

Stereo view of defect indicator 

Defect size ............................ 3 x 3 inches Depth belowLog diameter at defect (ib) ................ 15.8 inches 

Round-up thickness ..................... 0.3 inch Logsurface .............................. 2.8inches 

Core diameter ......................... 5.8 inches First sheet of veneer. ...................... 2.5 inches 

Defect distance above stump ............. 11.5 feet 
Figure 7 (Continued) 

Depth belowLog surface. ............................. 3.8 inches 

First sheet of veneer. ...................... 3.5 inches 

Depth belowLog surface. ............................. 5.3 inches 

First sheet of veneer. ...................... 5.0 inches 

\ 

Total Veneer Thickness .................... 5.0 inches 

Depth belowLogsurface .............................. 4.3inches 

First sheet of veneer. ...................... 4.0 inches 
regular bark pattern running lengthwise through the defect pattern of concentric circles encompassing the defect 

indicator. Also present can be moderate to well-defined indicator and "pucker-like" appearance of the center. 

breaks in the bark pattern running radially from the outer 

edges to the center of the defect indicator. Heavy bark All bark distortions result in some product degrade, but the 

distortions (Fig. 8) are identified by the characteristic amount of degrade decreases as the depth to the initial 

Figure 8.-Heavy bark distortion and associated internal defects. 

Stereo view of defect indicator 

Defect size ............................ 2 x 2 inches 

Log diameter at defect (ib). ............... 11.5 inches 

Round-up thickness. .................... 0.0 inch 

Core diameter ......................... 5.6 inches 

Defect distance above stump ............. 19.0 feet 

Depth belowLogsurface ................................ 1.Oinch 

First sheet of veneer ........................ 1.0 inch 
defect below the log surface increases. Light bark 

distortions, because of their greater depth below the log 

surface, are not considered defects in grading factory 

lumber logs, but medium and heavy distortions are. 

Figure 8 (Cc 

Depth belowLogsurface .............................. 2.0inches 

First sheet of veneer. ...................... 2.0 inches 

Likewise, many of the grading systems for veneer logs 

disregard light bark distortions. The clear area between the 

log surface and the defect is important in determining 

product suitability and, therefore, the log's economic value. 

sntinued) 

Depth belowLogsurface .............................. 3.3inches 

First sheet of veneer. ...................... 3.3 inches 

Total Veneer Thickness .................... 3.3 inches