APIS Volume 6, Number 9, September 1988
In this issue
- Using the Atago® Honey Refractometer
- Drying Honey Technology: Florida and Canada
- Marking Queens
USING THE HONEY REFRACTOMETER
There continues to be confusion surrounding use of honey refractometers. An enthusiastic group at the Florida Beekeepers Institute exchanged their ideas on this technology. The first thing the beekeeper should be aware of is that like with most technologies, the major variable is the human using it. How many of us have heard the statement, "the computer made an error." More likely the human operator of the computer made the error. The same will be true with the honey refractometer.
Those using a honey refractometer become comfortable with it only through a good deal of practice. This technology is also changing and what works on one instrument at a certain point in time can quickly become obsolete. This appears to have happened with the Atago® honey refractometer many are using. Older models came with a "test piece" to use in calibrating the instrument. The test piece had a number stamped on its surface and the refractometer was calibrated to that number. This is no longer the case. Those being shipped now come with a calibrating or LB fluid.
We looked at three new Atagos® at a recent meeting. Each looked the same, but using standard honey samples, they read differently. Only after calibration did they read the same. We now believe that frequent calibration is necessary. However, a hard and fast rule does not exist. Nevertheless, it is safe to say the more the better. Furthermore, we are now of the opinion that two instruments being calibrated at the same time give far more reliable readings when compared to each other.
This calls into question the use of any one refractometer and/or human operator at a particular time. Beekeepers not taking backup readings at the CCC warehouse or other point of purchase when delivering their honey are risking a great deal. Because of the number of potential inherent technical and human operator variables in measuring moisture content using the refractometer, a number of samples should be taken from different parts of a honey lot. These are then averaged together. The margin of error will be much less using such a technique. The more samples the less the error.
The current instructions for the Atago® hand-held honey refractometer confuse rather than enlighten the user. The instrument measures water content of honey directly based on the light that is refracted through a thin sample of the sweet placed on the prism. This is then corrected for temperature by reading the thermometer on the instrument itself and adding or subtracting the amount indicated. Unfortunately, the instructions provide an incorrect example. A reading of 18.7 with a plus 0.1 correction factor should be 18.8, not 18.9 as shown. Most refractometers do not measure water directly, but rather the solids in water in units called brix. Brix is used in the directions and shown on the LB calibration fluid, but is ignored when using a refractometer designed for honey.
Directions from the factory say that those whose instruments came with a test piece are to calibrate without reference to temperature. This means the corrective temperature scale on the instrument is ignored during calibration. The corrective temperature only comes into play when measuring the mositure content of a specific honey sample. The same is true of the LB standard fluid. The fluid, however, is more sensitive to temperature than the test piece and so a scale on the bottle provides calibration information correlated to the temperature of the instrument at a particular time. The range provided is from 15 degrees C to 30 degrees C. This correlates to 17.9 percent moisture for the former and 20.2 percent for the latter temperature.
Because the moisture spread is a small 2.3 percentage points, a crude guess during calibration that the room is 20 degrees C (68 degrees F) may be enough. However, in most circumstances a more accurate calibration is needed, especially where moisture percentage points mean more money. However, in order to calibrate the instrument using the fluid, a temperature reading of the room is required. In other words, ONE NEEDS A SEPARATE THERMOMETER. DO NOT USE THE ONE ON THE REFRACTOMETER ITSELF FOR MEASURING THE ROOM TEMPERATURE. In addition, some interpolation will be needed in case the temperature doesn't fall exactly on those listed on the LB fluid bottle label (15 C, 20 C, 25 C, 30 C). There is a fifteen degree spread between 15 C and 30 C and a 2.3 percent spread between 17.9 and 20.2 shown on the bottle. This means that the calibrated moisture will vary .1533 percent for each degree C. The following chart shows the relationship between each degree and amount of moisture rounded off to one decimal place.
Degrees C Calibration (honey water)
15 17.9
16 18.0
17 18.2
18 18.4
19 18.5
20 18.6
21 18.7
22 18.9
23 19.1
24 19.3
25 19.4
26 19.6
27 19.7
28 19.9
29 20.0
30 20.2Therefore, if the room and instrument measure 19 degrees C, the calibration is set so the line on the refractometer runs through the 18.5 mark. If the temperature is 26 degrees C, then the calibration is set at 19.6. I would appreciate any comments by readers who might add to this discussion.
DRYING HONEY: FLORIDA AND CANADA
Mr. Bert Kelley brought an interesting honey drying apparatus to the Beekeepers Institute this year (See September 1993 APIS). It consisted of a piece plastic pipe about 2 inches in diameter. A small copper tube was afixed to and ran down the outside of the pipe. The end was bent and inserted at the bottom. Thus, air is directed downward and then bubbles upward. The whole mixture of air bubbles and honey inside the pipe is lighter than the honey itself and so rises over the level of the honey on the outside of the pipe. At the top of the pipe, a short piece joins at a right angle. The concept is simple. The level inside the pipe rises enough to let the mixture pass into the top pipe joined at a right angle. This mixture is directed to spread out over some flat surface before dripping back into the barrel. This system recirculates the honey in a container and provides surface area for a dehumidifier to reduce its moisture. The air pump required is small. As an experiment, Mr. Kelley used an aquarium pump with success.
Although honey in a barrel is effectively dried using Mr. Kelley's method, it is often easier to dry it in the comb. Even comb that is capped is permeable to moisture, but it is much more efficient to have uncapped honey. The concept of taking honey off a colony before it was capped and then drying it in hot rooms was pioneered in Saskatchewan, Canada. Recently, the Ontario Provincial Apiarist, Douglas McRory, reprinted this information in his Apiculture Newsletter. Much of this has application for Florida where honey is traditionally high in moisture content.
Because honey equilibrates to 17.8% moisture (the most allowed in Canadian #1 honey) at 59% RH (Relative Humidity), best drying and storing conditions must be at or below 58% RH, according to the Canadian study. Relative Humidity is a relationship between how much moisture the air is holding and how much it can theoretically hold. This is written as a fraction or a percentage. 58% Relative Humidity means that the air is holding 58% of what it theoretically can hold (100%) or as a fraction 58/100.
The study shows that the wetter the honey the easier it is to dry. A drop in RH from 70% to 60% corresponds to a change in honey moisture content of 5.9% (24.2% - 18.3%). A drop from 60% to 50% RH corresponds to a honey moisture content change of only 2.4% (18.3%-15.9%). The bees use a combination of heat and ventilation to dry honey so why not the beekeeper?
The example given is that 1000 cubic feet of outside dry air (50% RH) holds .9 pounds of water at 29 degrees C in the daytime. When introduced into a honey house the same amount of air cools to 27 degrees C, but will equilibrate at 58% RH and so hold 1 pound of water. Thus for every 1000 cubic feet of air exhausted. .1 lb of water will be evaporated off the honey.
Removing more water is possible doing two things: (1) add more heat to raise the room temperature enabling the air leaving the building to hold more water and (2) move more dry air through the building in order to move out more water. The study recommends the latter as being less expensive in the daytime.
At night, however, the relative humidity rises as the temperature drops. The answer here is to heat the room. This is more representative of Florida conditions day or night. However, in Florida the RH is often so high that it is ineffective to simply raise the temperature of the room. What is further required is a dehumidifier. This is also discussed in the Saskatchewan study. The capacity of household dehumidifiers varies from 10 to 30 pounds of water per 24 hours (1/2 to 1 1/4 pound per hour), according to the study. A pint equals about 1 pound. To be effective, hot air must circulate through each super stack and across each comb face.
The study says overhead ceiling fans will greatly help to circulate the air. The recommendation for such fans is to have a 36 inch diameter fan for every 150 to 200 square feet in the building. Supers must also be stacked on side slotted pallets and some space left between rows to increase air circulation. Supers should not be stacked over five high; four high or less for wetter honey in supers. They can also be stacked on end. Frame spacers in honey supers also help circulate air within stacks. Ventilating hoods or small fans placed on individual stacks will also help.
Finally, the study suggests using a honey refractometer and good quality humistat. The former to determine the honey moisture content, the latter to monitor the RH. A summary checklist in also included to remind those of the basics in drying honey:
- Choose an exhaust fan or a combination of exhaust fans to cover both day and night ventilation needs.
- Use dehumidifiers, if desired. (In Florida, they are probably a must)
- Connect heaters to thermostats set at desired temperatures.
- Use overhead circulation fans.
- Ensure all comb faces are exposed to air movement.
- Use a honey refractometer.
- Keep the relative humidity as low as possible.
- Use hmidistats.
MARKING AND CLIPPING QUEENS
Each year at the Beekeepers Institute there are a good many questions concerning marking and/or clipping queens. Dr. Roger Hoopingarner in his "B- Plus" newsletter, Spring, 1987 sums up the answer: "The easiest way to find queens is to always have them marked." He suggests using model airplane enamel (we often use typewriter correction fluid) and provides a 5-year-color code that will give the relative ages of queens. The code is as follows:
Year Ending in Color
0 or 5 Blue
1 or 6 White (Grey)
2 or 7 Yellow
3 or 8 Red
4 or 9 GreenHe also suggests using the brighter and lighter color tones. The end of a straightened out paper clip will deliver just the right amount to the queen's thorax. Pick up the queen carefully using the wings then transfer her to between thumb and index finger. Clip either the right (even years) or left (odd years) wing and then paint the thorax. Be careful never to get any paint on the head. The rule here is to err toward the rear. Dr. Hoopingarner also says that clipping the queen's wing does not decrease her ability to lay eggs.
Sincerely,
Malcolm T. Sanford
Bldg 970, Box 110620
University of Florida
Gainesville, FL 32611-0620
Phone (352) 392-1801, Ext. 143 FAX: (352)-392-0190
http://www.ifas.ufl.edu/~mts/apishtm/apis.htm
INTERNET Address: MTS@GNV.IFAS.UFL.EDU
©1988 M.T. Sanford "All Rights Reserved
