Grading rules for teak veneer logs
The late 1950s saw the rise of the teak veneer market though the 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 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 (then known as State Timber Board) came into being are called the “Grading Rules for Teak Veneer Logs”, and are currently applied. Defects considered in the Gallant Rules and the Veneer Log Rules are shown below as comparisons:
Gallant Rules: Bear Bite; Bee Hole; Bend; Bird Hole; Buttress (no defect); Doyo; Drag Hole; Ellipse; Flute; Holes (End); Knots; Shakes; Shatter; Snout (no defect); Sun cracks, inbark; Twist.
Veneer Log Rules: Bee Hole; Bump; Curvature; Elephant Skin; End Flute marks; Flutes; Green band; Heart (Diagonal, Double, Spongy, Hole, End); Inbark; Knots (Sound, Pin,); Pig eyes; Pitch pockets; Shape (Elliptical, Triangular); Shake (Ring, Cup); Splits; Sun cracks; Twist; Wavy grain; and later inclusions - (Interlocked grain; Black spots; Sapwood pockets; Syphilis).
Permissible defects are scheduled according to the location and magnitude. These defects are then classified as either mild or serious. One serious defect (S) equals two mild (M) defects, and each grade limits 3S or 6M. In the Veneer Log Rules, log scaling, i.e. estimating the net contents of a log, which equals the gross or full contents less deduction for defects, is not taken into account. This is one difference from the preceding rules but like its predecessors, each log has to be graded separately.
One of the disadvantages in the log trade is that one has to sell only what was extracted. Up to the mid-seventies, a larger percentage of First, Second and Third quality logs were available for export. What was not exported in log form was used in the local mills. The 1980s witnessed an entirely different scenario when fewer veneer logs were obtained and more saw logs became available.
The need for introducing rules for sawing quality teak logs that do not fit in the previous rules engendered a new set of rules for sawing quality logs that are inferior to the 1 star class. Gallant rules require that logs are to be butted clean at both ends. The same applies to veneer logs. But the sawing quality logs sold today are unbutted and offered for sale as they come out of the forest. A comparison of dimensions is shown in Table 11.
Table 11. Gallant, veneer rule and sawing grade rules
| Gallant Rules | Min. Dimensions Length x Girth | Veneer Log Rules | Min. Dimensions |
| AY | L15' × G6' | Special | L15' × G6' |
| 4* | L15' × G5' - min. 30 cft | First | L8' × G4'2” |
| 3* | L12' × G5' - min. 30 cft | Second | L8' × G4'2” |
| 2* | L10' × G4' - min. 20 cft | Third | L8' × G4'2” |
| 1* | L10' × G4' - min. 20 cft | Fourth | L8' × G4' |
| - | - | Sawing Grade-1 | L8' × G5' - vol no limit |
| - | - | Sawing Grade-2 | L8' × G5'- vol no limit |
| - | - | Sawing Grade-3 | L8' × G3' to 4'11” only - vol no limit |
| - | - | Sawing Grade-4 | L8' × G4'- vol no limit |
Note: In Veneer Log Rules there is no minimum volume (vol) or cubic content specified provided the length (L) and girth (G) limits are met.
The sawing grade rules calculate the defect value as in Gallant Rules. But there is no log scaling. Each grade allows a fixed defect value. Grading is done according to the defect value considering the category of grade a log will fall into after the length and the girth are taken.
System of Sales
The current system of sales for logs in Myanmar is by tendering. But this does not necessarily preclude the need for a sound knowledge of grading, as lots are still bought and sold according to their grades. Teak logs coming from different areas have different values. Area consciousness on the part of buyers is very pronounced in this particular species. Teak logs from areas with heavy rainfall are less favored than logs from areas with scanty rainfall. For instance teak logs from Yamethin, Pyinmana, Pyay (formerly Prome), Minbu, and Yaw, are extremely popular. It has also been noticed that teak from Northern Shan State, and Momeik are also favoured. The reason for the partiality is that there are no typical defects in teak logs from these areas and the color, stripe and conformation of the logs rate from good to very good. Incidence of beeholes is markedly less in logs from the above mentioned areas.
Main Menu
Special Market Specifications
These specifications intended for dimensions stock such as Decks and Margin pieces , shall have only one grade in each case .
General Requirement : These shall be well manufactured with cross sections rectangular throughout ; sawn full , thickness and width being 1/8" ( 0.30 cm ) full to the normal dimensions at the time of milling ; fairly straight grained , sound and free from injurious worm or beeholes splits . shakes , sapwood , large knots not exceeding 1,25" ( 3.80 cm ) diameter or unsound knots , corner knots , ingrown bark , wane , heart centres , or imperfections due to heart centre , excessive discoloration and rot , or other injurious defects , unless otherwise specified.
Decks : Upper face and the upper half of the calking edge shall be clear . One perfectly sound knot , but exceeding 1" ( 2.60 cm ) in diameter for every 10' ( 3 meter ) will be allowed . For decks of 10' ( 3 meter ) and longer up to 20' ( 6 meter ) two knots will be allowed provided that the distance between the knots is not less than one-third of the length of the piece . For decks longer than 20' ( 6 meter ) , three knots will be allowed , and the distance between each should be at least one - third of the length of the piece