Ok first off fill the canvas with a light brown and apply FILTER>ADD NOISE set to monochrome and tweak the slider till you have a bunch of noise on there!!
Next its the oldest trick in the book, MOTION BLUR
After its blurred we need to bring out the grain so we UP the CONTRAST until it pops out!!
Next create a NEW LAYER above and with a Light Brown foreground colour and a Black background colour goto FILTER>RENDER CLOUDS. Next change the layer settings to OVERLAY, that gives us a nice rich colour and some tonal variation as well, neat eh?? ;-)
Now to add some lines (if needed) using the Dodge and Burn tool to DARKEN and holding the SHIFT button, draw in some dark dividing lines, go over them several times if needed, use various brush sizes and vary the weight if you have a pressure sensitive pen, if you havent got one, GET ONE!!
Now under those dark lines we want some hi-lights to make the edges pop out, so Holding ALT so the D n B tool lightens, Hold SHIFT as well if needed to make some lines below the dark lines, This is just to bevel the edges slightly...
A bit more work now, Added some Knots and scratches with the D n B tool, I also made the dark lines less regular so they have chunks out of em n stuff!!
Just an example of a few tweaks of the Hue, Saturation and Contrast/Brightness you can create Old Wood, New Wood, Oak Wood, Pine Wood etc. Have fun and I hope you found this lil tutorial useful ;-)
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