we always inspect frames prior to harvesting, and we have removed frames and soaked in hot water, soaked in napi san, blasted them with a high pressure hose, put them in a black plastic bag in the sun, frozen them and worked the mechanism… all with limited success. Over time the amount of wax, mold and propolis builds up on a frame and makes them unattractive to the bees. I spent a lot of time cleaning one set of frames prior to this season and was able to clean them up to a degree- but this season the bees have been very slow to work those frames and only fill them in a patchy manner. Bees have started filling new frames put in much quicker.
The bees do indeed clean up the frames and repair the wax after a harvest but that’s not really the issue I am contending with. Once frames are old and dirty and have a covering of wax everwhere the mechanism does not operate as smoothly- and entire columns of cells will not drain when the mechanism is operated. The clear plastic ends tend to start to warp a little too.
As I said - the only luck we have had it to entirely disassemble the frame and hand clean each and every row- then re-assemble. We are not sure yet how well these frames will work after this is done- and the last few I put back together I found the wires were very tight even with only one or two twists. I imagine this is due to a very thin layer of wax on the plastic that over the entire length of the frame makes it a few mm longer. That wax is very stubborn and hard to remove - even using hot water at 80c. It does melt but then it forms a layer over everything.
My friend who runs an urban beekeeping shop in NSW has had multiple customers bring in flow frames they no longer want. They have all had similar issues to what we are experiencing. I tried to harvest some of them out of the hive and had the same issues of entire segments not draining even though we use two keys and move them multiple times in the slot.
I am coming to the opinion that 5 years or so might be about the life of a flow frame. Unless there is some kind of solvent that can be used to clean them. Also it may be that cleaning them in hot water by hand- and replacing the wires with new ones- and new end parts may bring them back into service- but it really is quite a lot of labor to do that.
It may also be that by removing the frames over winter, only using them on strong hives, and during a good flow- that they could be made to last longer and work well for longer too. But that does require the use of a standard ideal or super in conjunction with the flow frames.