If you go to the trouble to build your own honey warming cabinet it’s worth ensuring that the dimensions allow you to also use it to warm super frames ready for extraction. This makes extraction more enjoyable (or at least much less painful?) because the honey flows out of the comb more easily. I use National hives, so my boxes are all 46 cm square. By constructing the honey warming cabinet with external dimensions almost exactly the size of two supers they can be stacked side by side with the lid inverted on top. The (hopefully considerable) weight of the supers is taken by the side walls of the box, not by the insulation. Most supers drip a bit of honey – perhaps due to broken brace comb between boxes – so line the cabinet with a few sheets of newspaper to catch the spills. Adjust the thermostat to keep the boxes at a gentle heat until you’re ready to extract them – in my case I usually collect supers over a couple of days and maintain them at about 38oC, rotating the pile once or twice to ensure they get warmed through.
My honey warming cabinet is 87.5 cm long – fractionally too short for two supers side by side (either a design flaw or dictated by the original pieces of wood I had available – too long ago to remember). However, I use quite a few Sweinty polystyrene supers which have very thick walls. By placing these at the bottom of the stack, overlapping the cabinet box ends slightly, I can ensure little heat escapes. My cabinet has a small mains powered fan circulating the air, ensuring good heat distribution through the stack of supers.
Extracting the early honey from oil seed rape (OSR) and hawthorn must be done before the honey crystallises – unless you’re going to melt and crush it out of the comb of course. This year I extracted over the unseasonably cold late May bank holiday weekend. Without some sort of gentle warming the honey gets viscous, making extraction both difficult and less effective. It’s a tiresome enough task as it is, so make it as easy as possible by pre-warming the supers.