Hi
I used to work with a commercial beekeeper here in Wisconsin.
His preservation method was a lot of paraffin [20-25 gal] and he used
"copper napthenate" (obtained from Dadant & Sons) he may have used
1 gal or so in the paraffin all the woodenware went in for 4 hours or so at
180* or so.  Sure does stink but that woodenware will never rot and the bugs
ants, termites, etc will never chew either. Never needs painting or
maintenance.
Never caused any problems with or for the bees.  Just wanted to post for
your info.
Jim Maus West Bend WI