Checking Honey Moisture Content and Drying Honey
Knowing the moisture content of your honey before harvesting is very important. Why? If the moisture content of the honey is too high, it can ferment. What level is too high depends on the yeast spore count of the honey. Pretty much zero beekeepers are submitting honey samples to a lab to check yeast spore counts, it's just not feasible. According to the USDA, honey with only 1 yeast spore per gram will ferment within a year at over 19% moisture. 1 yeast spore per gram would be unheard of, there will certainly be more yeast spores. Honey between 18.1% and 19% moisture with no more than 10 spores per gram is able to be safely stored. Honey between 17.1% and 18% with up to 1,000 yeast spores per gram is able to be safely stored and honey at 17% or less moisture content will never ferment no matter how many yeast spores are in it.
Image courtesy of USDA Beekeeping In The United States
The floral composition of the honey plays a part in how many yeast spores are present, some honeys will be safe at higher moisture content levels than I described above. For example, mangrove honey will not ferment at 19% moisture while cabbage palm honey can ferment at 18% due to its high yeast spore count. For wildflower honey in my area, 18% and under is safe. I'm generally shooting for 18% or under at extraction and then it's ~17% or so once I actually bottle it.
Some books will tell you honey is fine up to 18.6% but I do not trust that, 18% is the highest I will go and prefer to be under that. Beyond what is safe from fermentation, excess moisture will dilute the flavor, aroma and other properties of the honey. If you did a taste test on honey extracted at 21% moisture and then dried that same honey down to 17%-18% moisture and did another taste test, you'd find the lower moisture honey is richer and has more of that honey flavor we all love. Beekeepers want to produce honey that our customers love so they are repeat customers, and delivering a quality product to them that is safe from fermentation as well as has good flavor is paramount to that.
So how do we check the moisture of honey? We do that using a tool called a refractometer. They're quite affordable and are a must-have for anybody harvesting any amount of honey. I've heard some beekeepers say if it's capped it's good to harvest but that's simply not true. It might be at the right moisture content when the bees cap it but if you have a lot of rain in a season and relative humidity is so high that they bees can't keep it to 50%-60% in the hive then moisture will be absorbed through the wax cappings and end up higher than it was when it was capped. This season was a great reminder of that, I found several capped honey frames at over 20% moisture while also finding uncapped honey at 17%. The old wisdom of if it's capped its good and if it's not capped it's not good is not reliable and a refractometer should be used both before extraction to spot check and then after extraction to check what the final moisture content ended up being.
This reading at 19.5% was from a capped honey frame, too wet.
Refractometers need to be calibrated before using. You should follow the instructions for the refractometer you purchased to calibrate it, but generally speaking extra virgin olive oil is used for calibration. Instead of honey, you put EVOO in the device and then adjust the calibration to 71.5 BRIX. Clean off the device and then it's ready to check honey.
What do you do if you spot check your honey before harvest and it is too wet? Time to dry it and it's pretty simple to do. It is much easier to dry it when it is still in the frames as opposed to extracted as the surface area of it on the frames is much greater than it will be sitting in a 5 gallon bucket. You will need a clean room, some 2x4's, box fans, and a dehumidifier. Stack the supers in stacks of 6-8 on top of two 2x4's, which elevate the boxes off the floor and give a pathway for air to move through. Set a box fan on top of each stack and turn the fan on high. Get the dehumidifier going and keep the relative humidity at 55% or under. At 55% humidity, honey will eventually equalize to about 17.1% moisture though it will take a long time for that to happen. I really like to get the humidity pulled down to around 35% as once you are at that level with fans on top of the stacks you can drop the moisture level drastically over just a few days. If you really want to dry it quickly, 35%-40% range for humidity will work wonders. Temperature also matters, and you will have quicker drying at temps in the 85-90 degree range than you will at 70 degrees though both will work. I not only like to keep the humidity much lower than 55% for quicker drying, but also to avoid issues with small hive beetles. From what I understand, small hive beetle eggs need at least 50% humidity to be viable and you will hear people warn you about extracting within 3 days to avoid small hive beetle larvae from destroying frames of honey. I believe at 35%-40% humidity in your honey room you will have no issues with small hive beetle eggs hatching and larvae destroying your honey, especially with fans on the stacks moving large amounts of air, any eggs present would be dried out and non-viable.
Once you extract, if you check your honey and it is too wet, it's a bit harder to dry at that point. If that honey is in 5 gallon buckets in a dry room with the lid off then there is very little surface area to facilitate drying, it would take forever. You can speed that up with a couple of bottling buckets with gate valves. Put honey in a bottling bucket up high and then another empty one below it and placed so the honey from the top bucket drips into the lower bucket. Open up the gate on the top bucket just enough to have a steady stream of honey flowing but just barely and make sure it is dripping into the lower bucket. When I have done this in the past I have trickled it so slowly that even overnight the entire 5 gallons hasn't flowed through yet. Set a fan in the area blowing just beside the stream of honey but not directly at it as the breeze may blow the stream of honey so that it does not fall into the lower bucket. Once finished trickling, you can check the moisture level and I bet you find it has dropped at least half a percent. If you need more moisture removed then take the now full bottling bucket from the bottom and swap them and repeat the process until at the desired moisture content.
Moisture content of honey is very important, don't rely on the frames being capped as the sole indicator of being dry enough or not and definitely not "shake tests" some will advise you to do and claim if you shake the frame and honey doesn't fall out it's good. Refractometers are the best way to make sure your honey is a good quality product and will not ferment later down the road.