>4) There is a fresh supply of young bees and/or they have just swarmed.
>Only young bees make wax
Old bees can make wax. They are just not very effecient at it. If you have a hive with only older workers, with no where to store nectar, nectar coming in and enough heat to draw wax, they will make wax.
"Older worker bees can recover their ability to produce wax if the colony requires it ."
Temperal and spatial patterns of wax secretion and related behavoir in the division of labour of the honeybee.
This study took bees of known age and counted the percent with wax scales. The results by age and if they were festooned were:
Even young bees aren't that good at it until they get into the swing of things:
days festoon non-festoon
3 22.2% 36.7%
6 60.3% 42.5%
9 71% 56.4%
12 52.5% 40.5%
15 54.9% 28.9%
18 39.2% 23.9%
21 28.2% 13.7%
From Beeswax Production, Harvesting, Processing and Products, Coggshall and Morse pg 35
"Their degree of efficiency in wax production, that is how many pounds of honey or sugar syrup are required to produce one pound of wax, is not clear. It is difficult to demonstrate this experimentally because so many variables exist. The experiment most frequently cited is that by Whitcomb (1946). He fed four colonies a thin, dark, strong honey that he called unmarketable. The only fault that might be found with the test was that the bees had free flight, which was probably necessary so they could void fecal matter; it was stated that no honey flow was in progress. The production of a pound of beeswax required a mean of 8.4 pounds of honey (range 6.66 to 8.80). Whitcomb found a tendency for wax production to become more efficient as time progressed. This also emphasizes that a project intended to determine the ratio of sugar to wax, or one designed to produce wax from a cheap source of sugar, requires time for wax glands to develop and perhaps for bees to fall into the routine of both wax secretion and comb production."