I have come across an interesting effect that I hope one of you might be able to identify for me.

The other day I brought home a sawn piece of Queensland Hoop Pine 6″ wide(http://www.intad.asn.au/materials/wd_hoop.asp) to use as a peg rail inside – it carves well and ages to a really nice amber colour.

The major saw marks were pretty much straight across the board. I don’t own a jointer or a planer (pay to have it done for projects – the tools are on the want list) so I had to dress this board by hand. I removed the saw marks and got to smooth timber, but even with a good continuous translucent shaving taken with a 4 1/2 there remained discolouration in the timber.

The colour was a purple/brown set of close arcs running roughly 45* across the wood, exactly as you would expect to see from a circular saw. I had to revert to a coarser set jack plane to get rid of them and had the workout I missed because it was raining outside, so they were pretty deep.

Given that the wood was already smooth, the only explanation I can see was that this is water staining from sawing green timber. What is the real answer?

Dave