Teak Log Grading

Introduction
Grading is a value adding process as " adding value" is an action that adds worth to something through a specific process. Properly graded timber gives a value of worthiness and satisfaction to the buyer and graded timber of any species enjoys higher prices than ungraded timber. In the early days not many items of timber were traded and grading was mainly by rule of thumb.

Most countries and regions have their own sets of grading rules with different rules for different species; for softwoods and hardwoods. For example, the National hardwood Lumber Association(NHLA) Rules from the United States, the British Columbia Lumber Grading and Quebec Grading Rules from Canada, the Finish Grading Rules and the Malayan Grading Rules(MGR) are some of the well-known rules, to name a few. As a major teak producer, Myanmar has its own sets of grading rules for teak and grading of teak logs and lumber in Myanmar is done according to these rules. Until now there appears to be no collaboration regarding grading among the teak producers in the Region. Teak, whether in the rough or processed is still a natural product, and growth conditions are mainly influenced by soil and climate. Until a wonder technique has been perfected to produce finer specimens of trees, grading rules will remain the arbiter of what a piece of timber is worth.

Jungle Rejection Rules
The origin of the first modern grading rules for teak logs in Myanmar can be traced back to 1936. The Forest Department established the "Logging Rules and Standard for Jungle Rejection of Teak Logs" and the rules mention the measuring system. Logging system and system of rejection in the jungle. In short, the rules specifiy the calculation of defects for obligatory and optional timber. Mention of Grades is not noted in these rules.

Gallant Rules
The " Standard for Jungle Rejection " was followed in April 1998 by " Classification of Teak Logs ", popularly known as "Gallant Rules", as they were prepared by Mr. M.M. Gallant, Forest Economist of the Forest Department. This classification covers five grades; viz., five star( or AY), four star, three star, two star and one star. Like the standard for Jungle Rejection, and the Gallant Rules deduct five cubic feet per defect for scaling purposes. Star classes are graded according to the defect value and the limits determining the star class of a log are given in Table 1.
Table 1: - Star Classes and defect values
Note - Logs are graded by calculating the defects per 50 Cubic Feet.
Grading Rules for Teak Veneer Logs
The late 1950s saw the rise of the teak veneer market started much earlier. The quality of the logs harvested then was very good and therefore logs graded under the Gallant Rules were also acceptable as veneer logs, mainly because of the superior quality of the logs. Logs inferior in quality to those harvested earlier, increased in quantity as time passed. Market conditions also pinpointed defects previously not recognized. Aesthetic value is now being considered in addition to other quality defects. A new set of rules prepared by the Myanma Timber Enterprise (MTE) came into being are called the "Grading Rules for Teak Veneer Logs" , and are currently applied. Defects considered in the Galant Rules and the Veneer Log Rules are shown below as comparisons:

Myanma Timber Enterprise (MTE) has specified the Defects Classification as follows:

Major Defects
Bee Holes, Green Band, Branch, Heart Hole, Doyo Hole, Pitch Pocket, Double Heart, Wavy, Bump, Twist, Culvature Diagonal Heart.

Minor Defects
Cup Shape, Ring Shape, Flute, Inbark, Sun Crack, Spongy, Pinknot, Black Spot, Elephant Skin, Triangle shape, Felling crack, Elliptical shape.

Additional Defects
Inbark hole, Star crack, Waving ring, Ring close, Deform Gallstore, Heart crack, Side hole, water stain, Flute mark, Color dark, Heart spongy, Pig eye, White spot, White band.

Area of origin: Myanmar country map with hammer marks for teak logs
The quality of teak log is clearly influenced by the locality of where it has grown up. Each locality has its own soil quality, geography condition and climate. In teak log grading, there are Hammer Marks ( marking made by scribed by hammer) that show the exact place of its origin.

Although the Forest Department had not published a set of Rules for Teak conversions , the millers and shippers have used their traditional grades which are known and accepted in the markets at home and abroad .

The Myanma Timber Enterprise (MTE), which is reorganized from the previously-known State Timber Board(STB), taking over the extraction , milling and marketing of teak naturally, have to find grades common to the traditional offered under different marks and write up a fresh set of rules .

The present rules are based on Myanma Timber Enterprise practices and have been drawn up along the lines adopted by the Food and Agricultural Organlzation of the United Nations .

Teak conversions cover a wide range of products and it is not always possible to describe in detail the technical differences between the varlous classes , Planks boards , flitches , etc,.are usually exported in average dimensions and are mostly intended for re-conversion into rrequired sizes . On the other hand , decks , margin planks , special scantlings , flooring , etc,. which are generally known as "DIMENSIONS STOCK " have specialized uses and are usually used in sizes supplied and therefore have to follow special specification . The specifications ate therefore divided into :

• General Market Specification :-applicable in the case of Planks , Boards , Flitches , etc,. intended for reconversiopn , and
  


• Special Market Specification to cover Decks , Margin Planks , Flitches and special Scantlings .At the moment it is not proposed to include specifications of such categories as flooring strips , shingles water levels and railway keys but these may be added later if the volume of trade involved justifies their inclusion,.
  

Grading Officer are expected to study these rules carefully and use their best judgement in applying them , but they should not let their judgement suersede anything written specifically in the rules themselves .

 1. INSTRUCTIONS, REGARDING APPLICATION OF RULES, MANUFACTURE, MEASUREMENTS AND DIMENSIONS 1.1 GENEREL PROVISIONS 1.1.1 The grading of timber depends on the general quality of the wood and on the observation of visible defects, faults and blemishes and a judgment of the amount of waste which they will cause. It has been found in practice, however, that experienced graders will agree within 5% on the quality of any given parcel of timber. Graders are, therefore, instructed to study these rules and description carefully and use their best judgment in applying them. No grader, however, shall permit his judgment to lead him to a conclusion contrary to anything definitely stated in the rules and descriptions themselves.

1.1.2 The grade of any parcel depends both on the quality of the poorest square and on the average quality of the whole parcel. Graders at the receiving end are therefore forbidden to apply these rules and descriptions to a portion of any parcel. In all cases, inspection must be made of the full parcel supplied as any given grade.

1.1.3 Inspection is normally to be made under these rules and descriptions, and applied to the visual grading or squares as supplied. Graders are not to issue explicit certificates as to borer holes (including ‘beeholes’), grain, splits or stains, and are not attempt to certify particulars as to texture, moisture content, seasoning or weight.

1.1.4 These rules define: 

(a) The average quality of the whole parcel.
(b) The poorest square which can be admitted in any grade
It is essential; therefore, that when graders pass any square of the poorest allowable quality it must be offset in the average by one or more squares of superior quality

1.2 MEASUREMENTS  

Unless otherwise agreed upon between the buyer and the seller, sidings will be measured in inches at mid-length of the square; ½’’ and up will be counted as the next inch above, and less than ½’’ will count off. Length will be measured in feet; 6’’ and up will count as the next foot above and less than 6’’ will count off. The quantity of timber will be expressed in tons of 50 cubic feet and fractions of a ton or their metric equivalents. A table for converting measurements in feet and inches to the metric system and vice versa in shown in Appendix B.

1.3 DIMENSIONS 

The quality of the timber is not dependent on the sizes of the square. The sizes to be supplied in any parcel of any grading will be for agreement between buyer and seller and do not enter into the description for the grades contained.

2. DEFINITIONS AS APPLICABKE TO THESE RULES 2.1 Beeholes – Holes in wood caused by the larvae Xyleutes ceramic. A beehole is called a small beehole when it cannot be probed by an ordinary sized lead pencil, etc., about 5/16 of an inch (0.8 cm) in diameter, and is called large when it can be so probed.  

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2.2 Centre- The centre of a face and square is the central portion of the face excluding the margin.

2.3 Curvature- Deviation from the straightness along the length. This is measured at the point of maximum deviation from string stretched along the concave edge from end to end.

2.4 Ends- Of a square are two en surfaces

2.5 End Holes- Holes in the end of a square, generally along the pith.

2.6 Flute- A flute is a natural channel on the surface of a log running more or less parallel to its axis. After conversion of a log into squares a portion of the flute may remain on the surface and its depth is measured at the mid-point of its length

2.7 Heart- Same as pith. It means the soft core occurring in the structural center of a log round which the growth rings of a tree are formed. 2.7.1 Exposed – Deep longitudinal crack in the face of square developed along the heart. This is measured by the length.

2.7.2 Twisted (Crooked) – hearth which does not run parallel to the edge of a square as judged from its position on the ends.  

2.8 Heart Crack- Crack developing from the pith toward the outer portion. This is classified as follows: 2.8.1 Diagonal - Crack developing in a diagonal direction. This is measured by the projection of the diagonal on the small side of a square

2.8.2 Narrow Elliptical – Crack more or less elliptical in section appearing on the ends and running more or less parallel to the faces.  

Fig. I- ILLUSTRATION OF HEART CRACKS 4  

2.8.3 Star- Cracks developing in the form of a star; these are measured by the projection of the longest diameter on the small side of square.
2.8.4 Ring- Crack developing along the annual ring. Its circumference is measured by its projection on the small side of a square.
2.9 Inbark – Bark enclosed in the stem or a tree later growth; the remnants of such bark on a square are measured by their length.
2.10 Knot - Portion of a branch which has become embedded in the wood by the natural growth of a tree; the cross section of a knot is usually circular or oval in shape, and it is measured by its mean diameter. Knots are classified as follows: 2.10.1 Sound Knot – Is solid across its face and, except or its own pith, it is as hard as or harder than the surrounding wood to which it is firmly joined; it shows no indication of decay and is usually darker in color than the surrounding wood.
2.10.2 Unsound (Decayed) Knot – A knot which is softer than surrounding wood because it contains decay. If the decay is advanced there may be a hole in the center of the knot and the sides of the hole contain decay; Hollow Knot 
2.11 Margin – Margin area of the face of a square is a quarter of the siding from either edge and a quarter of the length from either end.
2.12 Rough Grain – Rough grain is coarse, knotty or twisted grain but now ordinary figured grain.
2.13 Sapwood – The outer layers of wood adjacent to the bark containing the living cells of a tree. This is generally lighter in color and is less durable.
2.14 Side Splits - Deep cracks developed on the sides; are measured as in Exposed Hearts.
2.15 Sun Cracks (Seasoning Checks) – Small cracks on the surface developed during seasoning.
2.16 Taper – A gradual diminution of thickness or width from end to end. The difference in corresponding dimensions at the ends is the measure of the taper.
2.17 Wane – Lack of wood along the edge of a piece of sawn timber. This is measured at its deepest portion. If this is present along both edges, the sum of the depths along both the edges will be the measure of the wanes.

3. UNIT OF DEFECTS 3.1 Beeholes 

1- large or 2 small = ¼ defect
2- large or 4 small = ½ defect
3- large or 6 small = 1 defect
4- large or 8 small = 1 ½ defect
5- large or 10 small = 2 defect
6- large or 12 small = 2 ½ defect
7- large or 14 small = 3 defect 
Note: The values given in this table are for defects in the center and ends of the face on which they occur. Beeholes in the margins have half the value of the above.

3.2 Curvature – Up to 1’’ in 10’ of the length will be admitted in all grades subject to the proviso that curved squares shall not exceed 5% of the number of squares in any parcel.

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3.3 End Holes – End holes up to 2’’ (5 cm.) in diameter or 10% of the siding whichever be less are no defect, provided they appear to run straight. En holes more than 2 ½ ‘’ (6.4 cm.) in diameter should not be admitted in any case.  

Over 2’’ (5cm.) or over 10% of the siding in diameter whichever be less, at one end. 1 Defect
Over 2’’ (5cm.) or over 10% of the siding in diameter whichever be less, at both end. 2 Defects 3.4 Equivalent Defects – Any defect not listed should be rated the same as a listed defect which appears to cause equal wastage of timber, e.g. birdholes should be rated the same as decayed knots, etc.

3.5 Heart Defects 3.5.1 Badly Twisted or Crooked Heart  

Badly Twisted or Crooked Heart 2 Defects
Note: If a square is penalized for twisted heart it should not be penalized for diagonal heart as well

3.5.2 Diagonal Heart Cracks

i. When present at one end and measures 1/5 to ½ siding = ½ Defect
ii. When present at one both ends and measures 1/5 to ½ siding 
or 1 defect

When present at one end and measures over ½ siding

iii. When present at one end and measures over ½ siding

and 1 ½ defect

When present at other end and measures 1/5 to ½ siding

iv. When present at both ends and measures over ½ siding = 2 Defect 3.5.3 Side Splits or Exposed Heart – Defects should be calculated as follows to the nearest quarter of a defect  

Length of exposed heart in inches

Volume square in cubic feet

e.g., exposed heart 18’’ long in square of 36 cu. ft. would be:

18/36 = ½ defect

Depth is immaterial.

(For measurements in metric system adjust the figure accordingly.)

3.5.4 Ring Heart Cracks

i. When present at one end and measures half ring up to 

½ siding = 1 defect

ii. When present at one end and measures half ring over  

½ siding =1½ defect

iii. When present at one end and measures half ring up to  

½ siding

or, = 2 defects

When present at both ends and measures half ring up to

½ siding 6  

iv. When present at one end and measures half ring over  

½ siding

or, 2½ defects

When present at both ends and measures half ring over

½ siding

v. When present at one end and measures half ring up to 

½ siding

and, 3 defects

When present at other end and measures half ring up to

½ siding

Note: Full ring hearts at both ends should not be admitted

3.5.5 Star Heart Crack or Soft Heart

i. When present at one end and measures 1/5 to ½ siding = ½ Defect

ii. When present at one end and measures over ½ siding  

Or, = 1 Defect

iii. When present at both ends and measures 1/5 to ½ siding

iv. When present at one end and measures over ½ siding

And, = 2 Defects

v. When present at other end and measures 1/5 to ½ siding

vi. When present at both ends and measures ½ siding =3 Defects 3.6 Inbarks and Flutes – Shall be rated as follows:  

Length of inbark in inches

Volume square in cubic feet X 2

Defects per inch of depth (to the nearest ¼), e.g., inbark 18’’ long and 1’’ (or less) deep in a square of 36 cu. ft. would be calculated as follows:

18/36X2 = ¼ defect

If the inbarks were more than 1’’ deep but no more than 2’’, it would be:

18X2/36X2 = ½ defect

(For measurement in metric system adjust the figure accordingly.)

3.7 Knots – (To be measured by mean diameter.)

One knot up to 1’’ (2.5 cm.) =1/4 Defect

One knot over 1’’ (2.5 cm.) up to 2’’ (5 cm.) =1/2 Defect

One knot over 2’’ (5 cm.) up to 4’’ (10 cm.) =1 Defect

One knot over 4’’ (10 cm.) up to 6’’ (15 cm.) =1 ½ Defects

One knot or cluster of knots over 6’’ up to 8’’ =2 Defects

One knot or cluster of knots over 8’’ up to 10’’ =2 ½ Defects

One knot or cluster of knots over 10’’ =3 Defects

Note: The values given in this table are for defects in the center and the end portion of the face on 7

which they occur. For such defects in the margin, take half value. Decayed knots count twice as much as sound knots.

3.8 Rough Grain

Rough Grain (per face) =1/2 Defect

3.9 Sapwood – Sapwood up to 25% of width on the face on which it occurs, will not be considered as defect. Sapwood in excess of this limit will not be accepted.

3.10 Seasoning Checks – Ordinary seasoning checks, suncracks, etc., shall be permitted unless of so serious a character as to damage the timber. Serious, deep or open seasoning checks will be taken as defects as listed in these rules.

3.11 Suncracks – Suncracks (per ½ face longitudinally) = ½ Defect

3.12 Taper – Up to 1’’in 10’ (both faces) of the length will be admitted in all grades.

3.13 Wane – Wane, including sapwood, up to total of 25% of which on the face it occurs, will not be considered as a defect. Wane, including sapwood, in excess of this limit will not be accepted. Wane should be measured at its deepest part on each face.

A summary is given in Appendix A.

4. GRADES

General Requirements

All squares passed under these rules shall be of good, sound wood, reasonably straight in grain and free from objectionable spongy wood. Squares will be graded by determination of the standard defects given in Section 3 which are also given in a tabulated form at the end for ready reference (Appendix A.)

5. GRADE NAMES