I have more or less given up using sheets of foundation and find  that:
1) the bees produce a variety of sizes of worker comb ranging usually from  
about 5.0 in the middle of the brood nest to maybe 5.4 on the periphery (at Lat 
 50 N). Occasionally some 4.9 is found. Probably about 5.2 would be typical. 
The  last time I measured some boughten foundation it was 5.7.
2) the slabs of brood seem much healthier with far fewer misses.
3) I am beginning to notice in some hives that the bees are not uniform in  
size, and
4) the hives with different sizes of bee in them seem to be doing better  
than those which have more uniform bees.
 
Chris



   

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