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Best relative humidity for a veneer operation?3/21
We do a lot of veneering, and have a humidification system in the plant. I have run it at various settings, but generally between 30 and 40%. Does anyone have an accepted best value for this? We have about 25,000 sf, gas fired heaters, if that makes a difference.
Most humidification companies I have contacted recommend 50% or higher.
A different approach to the issue is what m/c should your veneer be prior to pressing. We find that about 9-10% is about right. When you have a sheet of veneer on a table or the top sheet of a log, does it stay flat or curl ? If it curls there is a good chance the R/H in your veneer area is too dry. This assumes that the log came in properly dried, That always needs to be watched. We recently opened three crates of basswood crossbanding material and every sheet was moldy ! This was custom cut and I guess they forgot to run it thru the drier.
For the casual reader: the moisture content above is based on using a hot press which essentially dries the veneer to 6-7% when used.
What issues are you guys having that prompts your question?
Charles: thanks for the help. The question was prompted by issues when veneer is stored, particularly trying to make use of leftovers from our initial purchases. We have no problems with veneer used a couple of days after receiving it, but if it sits around for weeks or months then it gets very dry, brittle, and distorted and it becomes very difficult to work. Our humidifier is not working properly, and the rh in the shop was in the teens in the last week. I will be getting the humidifier repaired, but was looking for guidance as to target rh to set for normal use.
Oh. That's easy. We keep out veneer wrapped in plastic and strapped into the crate we receive it in. That pretty much does it. It also keeps keeps the light off so stuff does not darken as quickly.
While my experience with veneer is null, I have paid close attention to what Gene Wengert has written regarding EMC (equilibrium moisture content).
If you can determine what moisture content
Below is a list from a forum response Gene made a number of years ago - it shows the humidity needed to maintain a given moisture content.
Hope this is of some help
19 to 25% RH = 5% EMC