I run a veneer board slicer. We slice 6 boards at a time, and lately I have been having a problem with blue stain on red oak. I can't run acid water with the oak either. The entire machine is nearly redone in stainless steel. The blue always shows up at the end of the run, ranging from the last 3-10 sheets or the entire book. I stop and clean the machine till it's spotless, a little before the run is over and at the beginning of the next run. Is it possible that it is in the wood itself? On one run, 5 boards of the exact same length and width got blue stain as one that didnít.
From John Van Brussel, forum technical advisor:
I think the blue stain is coming from the knife and the nosebar. The knives are usually chrome plated, but once the knives have been sharpened, the edge is revealed, which is high speed steel. The blue stain can be removed by washing with an oxalic acid solution.