Some tips on making and deploying candy boards.
Saw a couple things of interest in the photos above:
1. That's A LOT of sugar down on the slider boards. At least it's a lot compared to what I see in my hives. And, the sugar up in the candy boards looks like it might be loosely packed?
One thing I do to keep the bees from treating sugar like garbage is to pack it down during candy board prep with a rolling pin:
Russell Deptuch introduced us to this style candy board maybe 15 years ago and he made the point that it's important to pack sugar down. A marble rolling pin works best for me. Palms and fingers work, too. I've read reports from beekeepers who just pour loose sugar on the inner cover and then have the same problem with bees throwing it out of the hive.
The bees have to work harder to "mine" sugar when it's packed down, dried completely and hard all the way through. It's usually a mistake to "humanize" bee behaviors, but I feel like this technique makes the sugar more precious, more like food and definitely harder to harvest. So, not as likely to be thrown away. It only takes a few seconds to pack it down and the results seem worth it. I'd be alarmed if I saw that much sugar on the sliders and be trying to figure out why.
Drying candy boards works best when they're stacked by a wood stove with a small fan blowing over the drying boards, set on lowest speed. Heat and slowly moving air usually dries them out in 24 hours. If you can make a dent in the surface by pressing with a finger tip, the sugar isn't dry enough.
2. The candy board frames in the OP photos appear to be 2, maybe 3 times deeper than they need to be. This allows a large volume of warmed air from the cluster to rise up above where the bees really need it around the brood cluster and out at the sides and corners of the top box where bees are still foraging on capped honey, syrup and stored pollen.
This is the same reason I don't use quilt boxes. I want the bees to get full use of the air they've worked so hard to warm up. I try to keep any airspace above the winter cluster to a bare minimum. This also makes it possible to get winter insulation closer to the winter cluster. It's useful to be able to think how the bees use "space" to best advantage.....very different compared to human notions of space.
With candy boards about 1½" deep, you can pack in 8-10 lbs of sugar. That leaves just about ½" space between sugar and inner cover compared to what looks like 3-4" of open space in the photos. Keeping the sugar relatively warm makes it more inviting and easier for the bees to work on. That all-important "bubble of warm air" at the top of the winter hive is worth preserving by any means possible.
It would take a lot of bee power and fuel (honey/sugar/syrup) to heat that unnecessary 3-4" of empty space. It also puts the potential top entrance a lot farther away from the cluster. Bees use that top entrance because it's closer to where they live and raise brood in winter. But, if a top entrance is too far away, bees might keep using the lower front entrance, which also takes more effort and energy. Conserving energy raises the odds for winter survival.
I'm guessing your candy boards could be cut in half horizontally, maybe even in thirds, instantly giving you extra frames for new candy boards and doing the bees a favor by reducing heat loss. Quick job on a table saw, watch out for screws and nails at the corners.
3. Sometimes bees won't use the top entrance because they are stubborn little cusses! One of my nine hives has completely avoided the top entrance this winter. I can't see any obvious reason, but am planning to measure vent stick and upper vent area when the weather warms up. Maybe it's just some dumb oversight on my part.
Remember the "hive tool trick," where you stick the sharp end up between the top box and the outer cover flange at the back of the hive, then pull back on the shank. This pushes the inner cover as far forward as it will go and pulls the outer cover as far back as it will go, all in the same movement. This is only possible if the outer cover has enough horizontal "slop, about ½" in all directions as it sits on top of the hive. If the fit is too tight, a top vent is still possible, but the bees can't squeeze through.
I know these things seem minor. But, it's a large collection of small effiencies that make the difference between sustainable beekeeping and standing in line for replacement nucs every spring. It's tedious work figuring out these tiny advantages for the bees. Even more tedious making sure all those advantages are in place when they make the most difference during each particular part of the bee season.
Even Mr Meticulous gets a little crazy making sure the hives are set up "right." I put it in quotes because "right" is a moving target, changing with hive location, seasonal weather, forage conditions, etc. Still, I do believe there's a "better way" to manage each individual colony based on its particular needs. The trick is finding the way, Grasshopper.......