Mixing size species and mc in the kiln

[forrestM]

I am planning to dry 1000 bdft of 5/4 and 4/4 ash from 20% down to 6-8% and the customer would like to throw in 3 pieces of walnut he wants kiln dried for a mantle. The mantle pieces are 5x7 and 3x5, and just sawn/green. 

I imagine I don't want to mix them, and I can just tell him no - but if I am planning to sterilize this load, could I put it in at that point? 

Is there any way to combine them, or is it just a no go?

[Ianab]

It's likely possible to mix them, but you have to dry at the schedule of the slowest drying wood in the mix. I bet a 5" thick green walnut needs a much gentler schedule than 1" Ash? That means your whole load is going to take a whole lot longer. 

If you push the thick walnut through at the air dry Ash rate it will probably be ruined. (surface checking etc) 

If both were "air dry" the difference in schedule would be less, and probably acceptable, but the thick green walnut is just too easy to ruin. 

[Southside]

Like Ian said, you will wreck the mantles.  If you only put them in for the HT you will wreck them faster.  There is a reason mantles sell for higher money - because they have to sit around for a long time to be ready to use.  

Had a guy but an oak "mantle" from me last fall - I told him it was dead green and he said that was fine, I charged him RR tie price, not mantle price.  Well, he ran the heater under it for a week or so when there was no power and she split, twisted, warped, and basically tore herself apart and for sure the temps were not even close to what your kiln will be.  

[K-Guy]

At Nyle we don't recommend mixing thicknesses ever. As for mixing species, you can as long as they are in the same wood group in the drying schedules but you dry at the rate of the slowest drying wood.

[forrestM]

THat's what I figured! How dry do you typically go with mantle pieces? 5x6 and 3x5 I think it was. and what kind of schedule would you even use for material that thick? 

thanks,
forrest

[Southside]

Air dry them and forget about them for several years.  

[Ianab]

Air dry them and forget about them for several years.  

Basically this. After a couple of years they should be down around 15%, and you can safely put them in the kiln for quick finish drying / sterilise cycle. 
Otherwise you need a fancy vacuum or microwave kiln. They can dry thicker wood in a sensible time with magic science. But magic science isn't cheap.