I have served on the exams board for many years and have never seen matchsticks even mentioned in a marking scheme of a module 1 paper.
even so, I still use matchsticks under my glass crown board to prevent condensation drips.
that may work, but it's solving the symptoms rather than the cause.
Condensation is caused by the surface temperature of the glass being much lower than the air temperature inside the hive, and cooler air having a lower relative humidity than warmer air.
When the humid saturated air touches the glass, the air is cooled, the relative humidity falls, and the water vapour condenses out.
Introducing top ventilation then allows convection currents to flow, removing warm air from the hive, this has a number of effects:
- it reduces the temperature of the air inside the hive, this reduces both the water carrying capacity of the air and the temperature difference between the air and the glass, so reducing the condensation.
- the increased air flow also encourages evaporation, the rehumidified air escaping through convection/ventilation.
If the glass temperature was the same as the air temperature then there would be no condensation to begin with.
Q. How would we do that?
A. Lay a sheet of insulation on top of the glass.
With reduced conduction through the glass, the surface of the glass will warm and stabilise at a temperature much closer to that of the air inside the hive, rather than the outside temperature.
Result:
- little or no condensation on the glass
- no top ventilation needed
- more warmth available to keep the glass warm
- hive air temperature is not lost through ventilation
The two methods both work by reducing the temperature difference between the air inside the hive and the glass, which results in less condensation.
The matchstick method equalises the temperatures of the hive air and the glass by lowering the air temperature inside the hive to that of the glass.
The top insulation method equalises the temperatures of the hive air and the glass by raising the glass temperature to that of the hive air.
The mathematically challenged should look away now...
A matchstick is approximately 2mm in diameter, a national crownboard is 460mm square.
The ventilation area around the edges of a coverboard provided by a matchstick at each corner would be:
((460 - 2) x 4 x 2) = 3664 sq mm
That number probably doesn't mean much so if we provided the same ventilation using a mesh covered round hole in the centre of a coverboard, how big would it be?
The typical wire mesh used for hives has a open free area of approximately 80%, so the matchstick ventilation would be equivalent to a mesh covered circular hole of:
(((( 3664 x 100 / 80 ) / pi )**0.5 )* 2) = 76mm diameter
or in old money, a round hole of 3" diameter.