Adding moisture to Older logs

[Clarkstonkilnguy]

We have been having an issue with older logs pruducing lumber that peaks on the TCS system at 27% moisture.  Would there be a way to run a conditioning at the beginning of a run to relax the cells of the wood, and allow it to release some of the moisture at the core?

[MichaelM]

Some people think steaming at the beginning of the cycle does exactly what you suggest.  I have never been able to see it or measure the effect.  It does go against drying theory, but let's skip that because drying theory does not account for changes in the cell structure of the wood.

I'm a little confused - the TCS measures multiple boards while the unit is drying in the kiln.  Do you have wet units or some wet boards within the units?  Does the TCS never get below 27% and what do these same units measure at the planer?  Is the calibration of the TCS different for the lumber from the older logs? 

You could probably test this with little cost or risk.  I assume you now keep the vents closed and spray off while coming to temperature. Create some matched pairs of kiln charges (have the lumber as similar as possible between pairs).  Dry one of the pair in the normal way and keep the vents closed an extra 12 hours on the other. Use the normal schedule after that.  Follow each to the planer and compare MC variability (accounting for differences in final MC).  You should know after a few pairs of charges if the steaming is helping.  I'd avoid steam spray during the process, assuming the kiln is tight.

I would not do any of this if the lumber is already surface checked because it may make it worse.  Also, you did not mention species, but stain could be increased.

I'd be very interested in the results.  PM or call me if you want to talk about it.