Grade 1 C
Birch timber, PLANED both sides (S2S), kiln dried to 6-8%
moisture content (KD 6-8%)
1. The minimum required yield of clear wood cutting area for a front face of a 1C grade board is 66 2/3% - 83 1/3%. The minimum dimension of clear cuttings for the both faces of 1C grade board: 76 mm x 915 mm or 102 mm x 610 mm. The boards of 1C grade with surfaces less than 0.19m2 in area must have 100% clear wood cutting yield at a face. The boards of 1C grade with surfaces 0.19m2 - 0,28 m2 in area must have 75% clear wood cutting yield at a face.
2. Required proportion by width: the 1C grade boards of 152mm width and wider as well as of 127 mm and 102 mm widths are stacked together evenly combined in packs to be sold out as a mix in 50:50 ratio, as follows: the boards of 152 mm widths and wider shall amount to minimum 50% of the total volume of the goods shipped. The amount of narrow boards of 102 mm widths combined with 127 mm wide boards shall not exceed 45% of the total pack volume.
Required proportion by lengths for each order: the lengths from 2440 mm to 3960 mm shall amount to minimum 80%, and the lengths from 1830 mm to 2135 mm shall not exceed 20%.
3.Ready made dimensions for the 1C grade (measured after kiln drying and planing):
152 mm and wider: 24 mm x 152 mm and wider x 1830-3960 mm. Width tolerance -0/+152 mm.
127 mm: 24 mm x 127 mm x 1830 mm – 3960 mm. Width tolerance -0/+24 mm.
102mm: 24 mm x 102 mm x 1830 mm – 3960 mm. Width tolerance -0/+24 mm.
Thickness of a timber after two sides planing (S2S) with hit or miss (H/M): the thickness of planed boards shall be 24 mm. Unplaned areas of a 24 mm board shall have sufficient thickness to enable further processing in the USA for planing till the next standard thickness of 20.6 mm. Hit or miss shall not exceed 1/3 of each face surface area.
Length: the kiln dried timber shall be trimmed on both ends.
Length of boards and packs are calculated in integer foot values and fractional part is omitted (e.g. a board of 8'6'' (2615 mm) length is recognized and marketed as an 8' long board (2440mm))
4. Colour tolerance for the front face of the board: the clear cut front face is not permitted to have false heartwood (reddish or brownish).
Colour tolerance for the back/worse face of the board: It is permissible to have unrestricted amount of false heartwood (reddish or brownish) on the back/worse face of the board. Note: commonly false heartwood amounts to average 15% of the board's worse face.
5.THE FOLLOWING FLAWS ARE INTOLERABLE: black knots, splinterings, stains/dark marks of stickers, bluestain, decay, loose heartwood, square heartwood, checks, wane (bark), excessive mineral veins and flecks (single mineral strips of maximum 5 cm length are not recognized as flaws).
Kiln dried boards shall be sawn and planed.
Any kinked, contorted boards with dimples are not permitted.