Originally Posted by
John Samuel
Pete,
That's interesting.
It leads to a question; what is more important, that the veneers are dry or that their moisture content is uniform?
I ask because of an experience with a client who made ply, many years ago. Their line was going crazy because of the variation in moisture of the rotary cut veneers. Veneers from the outside of the log tended to be wetter and hotter than those taken from the heart of the log (more steam penetration near the surface of the log). After slicing, they went through a drier, but some veneers came out too dry and brittle whilst others were not dry enough. This caused a multitude of problems, not the least of which was sheets of ply trying to turn themselves into propellers.
The solution was simple; to stack the cut veneers before the drying line and give them a short period of steam heating to deliberately make them all wetter. The benefit was that the steam had the effect of making the moisture content of the veneers more uniform, because the dry veneers picked up more moisture faster than the wetter veneers. Then they could be passed through the drier and because moisture was pretty uniform going in, it was pretty uniform coming out. Problem solved. No more propellers, and a big reduction in complaints and rejected product.
So, to return to the question. Which is more important when preparing end grain veneers; to get the veneers dry, or that they be uniform in moisture content?
Cheerio!
John