I’m not sure if this question is appropriate but I see mold and stain as very closely related. 

So here’s my mold question:
What levels do you set your inline moisture meter at for a southern yellow pine to avoid mold in the summer season?

Hi Neissa,
You don't really "set your inline moisture meter" to any particular value.  You can assign markers to fire sprayers or tipple gates to maker or drop out wet lumber, etc...  But, you can't set your moisture meter to achieve any particular drying average. I think what you meant to ask was "what is the target mean MC one strives for to prevent mold in SYP in the summer season?"  If so, I think that is, as they say, "the million dollar question"

Drying is of course a trade of over-drying and under-drying as there are costs, both real and opportunistic in both directions and mold growth cost is of course weighed in the upper direction of under-drying (or having too high an average MC).  I can tell you that if you target an average MC of 10% then there will be no mold growth (or perhaps a little on some few boards in the upper tail of the distribution), however, the overdrying costs of degrade, etc... will far outweigh that achievement of no mold.  So, there is a balancing act from a business analytics approach.

Wagner spent years of research and development with multiple mills and with Mike Milota to produce analysis tools we call "Sweet Spot Technology"  We were recently awarded a patent for these tools as they use inputs from the mills on business data and our inline moisture measurement systems data to actually determine the optimum drying target for every particular product and kiln.  Kilns usually have slightly different variance to their drying distribution and this can affect the optimum mc target from kiln to kiln.  Our tools will also track and adjust optimum drying targets with seasonal and lumber diet changes as well as alert kiln operators to system performance degradation resulting from potential mechanical issues in a kiln or from other issues.

Probably a lot more than you were seeking, but I wanted to make clear the importance of taking in all variables aside from just potential mold growth in determining a target MC.

You have to be a lot more careful in the summer.  I can't give you an absolute value, but if you might set the drop out at 23% in the winter (leaving in some pieces over 19%) you might need to set it at 21% in the summer (leaving fewer wets so the number of potential sites for mold is reduced).  When you do this you are really pushing the edge for the occurance of mold and for passing SPIB inspections and any reinspections.

If you do not drop out, then you have to adjust your drying times if you want to have a similar effect.

Keep in mind that any piece over 18 or 19% is a potential site for mold and by the time the pieces get to 25 or 30% mold on that piece and the ones surrounding it in the package is likely.

Mike M.