>Yet some of the best beekeepers I know dip the entire box in paint to
achieve thorough coverage inside and out.

Including Keith Delaplane in his video: “Honey Bees and Beekeeping” if I
may add.

Also for those morbidly concerned with contamination, Mann Lake offers
copper quinolate for sale on page 18 of their current catalog. The product
is said to be suitable for wood that is in contact with food. Unfortunately
for the beekeeper with only a few hives it is sold in the five gallon size
for $236 U.S.

As for me, I just paint the outside and let the bees paint the inside.

Regards,
Dick