Paraffin Wax Dipping

New Zealand beekeepers have been dipping beekeeping equipment in hot paraffin wax as a means of preservative for almost 100 years. The other use of the hot paraffin dipper, for sterilising gear from AFB-infected hives, probably developed in the 1940s.

The first mention of paraffin wax dipping was by W.B. “Billy” Bray (Canterbury) writing in his own magazine “The NZ Honey Producer”. After a visit to Taranaki, Bray wrote that Allen Bates (Kaponga) was hot dipping supers and other hive parts. Bray suggested pre-heating the boxes in a hot room before dipping to provide better penetration of the wax. Bates also showed him lids covered with petrol tin material (tin plate) that had been starting to rust. By paraffin-dipping them, he had “added years to their usefulness”.

Bates’s dipping equipment and method were not described. It would likely have been some form of drum or vat, mounted directly above an open fire, perhaps with some form of brick or block surround to contain the fire. Steel forty-four gallon drums, when they became more widely available, were commonly used by beekeepers. The drum would be cut in half vertically, giving two half-round sections/ Concrete blocks could be placed to create a firebox area, and the drum simply fitted on top of that.

The first description of the operation of a wax dipper came in the late 1930s. Department of Agriculture Apiary Instructor David Robinson (Dunedin) described a shallow tank to dip one super at a time. Though the container was 1 foot deep, it was operated with only 4 to 6 inches of wax depth, presumably to allow for the rapid expansion of paraffin when it reaches too high a temperature. Robinson described a short immersion time of 15-20 secondes per side, turning the box four times to complete the operation.

Robinson said a box would absorb just under a pound of wax, less costly than two layers of paint, with less labour involved. The dipping was, for the most part, seen as an alternative to painting, rather than an addition.

Only nine years after the practice was first publicised by Bray, Robinson said there were “many hundreds of supers dipped in boiling wax” in New Zealand.

It was probably during the 1940s that beekeepers recognised that wax-dipped equipment that had been infected with AFB would not lead to new infections. The recognition of the value of wax dipping for sterilising equipment may have been slow, as the time and temperature requirements for sterilisation are greater than that required for the preservative effect.

In 1950 the preferred method of sterilisation for AFB-infected equipment was dipping in a hot “wood oil” mix, often in conjunction with various methods of scorching the insides of infected boxes. “Wood oil” was also known as tung oil or Chinese wood oil and was widely-imported, mostly as a replacement for linseed oil. Wood oil has a higher “flash point” than paraffin wax, so was considered somewhat better from a fire safety point of view. Beekeepers who would choose to use paraffin wax were still advised to talk to their local Department of Agriculture advisor.

The use of hot paraffin dipping for AFB-infected equipment meant that while the bees, frames, wax and honey would be destroyed, the beekeeper could sterilise all of the boxes, lids and floorboards by hot paraffin wax dipping. (The practice of scorching the inside of an AFB-infected box continued into the 1970s, most generally as an alternative to wax dipping, rather than in addition to, and it was eventually banned as ineffective.)

In 1953 apiary instructor Sid Line described paraffin wax dipping in Southland. Most of the article relates to painting supers with creosote or some wood-stains used in furniture work before the wax dipping. The article notes the importance of dipping dry timber and describes similar, but slightly larger, dipping tanks than the earlier article by Robinson. The tank is built to hold two or three supers at a time, laying on their sides and being rotated every 10 seconds or so. As with Robinson’s description, the tank was not designed to totally immerse a super, but rather had paraffin wax to a depth of only 4 inches. Line described boxes dipped more than 20 years ago (making it about 1933) still being used in Southland, with less warping than those that had not been dipped.

Line’s article contains the first mention of the use of paraffin wax dipping for AFB sterilisation. He recommended 10 minutes immersion at 316 deg F (158 deg C), very similar to figures that were mostly adopted (without any research to confirm) for more than 40 years. In 1998 Dr Mark Goodwin looked closely at the times and temperatures needed for paraffin wax dipping to be thoroughly effective. He found that 10 minutes at 160 deg C killed all spores, but lower temperatures or shorter times left some remaining viable spores.

Sid Line (then in Hastings) produced another article about wax dipping in 1964. He described a wax dipper built by Russell Berry (Havelock North) that involved a long “trough” tank, with guide rails to ensure the equipment would be completely submerged. An old boiler was cut and welded to provide the firebox for a wood fire. The immersion time for the dipping was controlled by how fast the boxes would be pushed through, and drained and painted at the other end. Throughput was estimated at 100 boxes per hour, giving each a 36 sec immersion in the wax.

A few years later Vince Cook (Oamaru) described Fred Bartrum’s (Pleasant Point) dipping tank, based on Russell Berry’s design. The heat transfer was aided by the use of 14 two-inch diameter boiler tubes. The device was heated by home heating oil that was drip-fed from needle valves. Cook considered that 316 deg F (158 deg C) was a suitable temperature for both preservation and sterilisation. He described that as the temperature at which white smoke begins to rise from the surface of the melted wax. He suggested that 2 minutes immersion at that temperature was appropriate for preservation, but that 10 minutes was needed for sterilisation. He estimated the costs for preservation as about 6 cents for a full-depth box.

Several paraffin wax dipping tanks were described in the NZ Beekeeper magazine through the 1970s and 1980s.

In 1978 Apicultural Advisors Murray Reid (Hamilton) and Andrew Matheson (Nelson) described a vat-type dipper made by Norm Findlay (Ohaupo). To assist in heat transfer, the chimney was fitted directly above the fire box. That did mean, however, that there was some challenge as the boxes had to be lowered over the (relatively short) chimney. It also restricted dipping of floors and lids. This type of “vat” dipper was simpler to construct than the “push through” units, and was designed for a smaller beekeeping operation. The dipper needed less paraffin wax to fill it when empty, due to the space taken by the chimney. The method of heating ensured that there were no “cold spots” due to uneven heating, a problem with some dippers. Findlay’s unit was used to dip two full-depth boxes at a time, and the boxes were painted with a water-based paint after excess wax was drained off for a short period of time.

A few years later in 1980 Andrew Matheson (Nelson) wrote about similar dippers constructed for Keith Detlaff (Ross, Westland) and Rex Bolwell (Riwaka). Detlaff’s unit had a brick surround to provide the double skin to contain the wood fire and provide some operator-relief from radiated heat, and an extension at the rear of the firebox to house the chimney. The dipper would hold 85-90 kg of paraffin wax when filled to within 125 mm of the rim. Matheson suggested that a temperature of 160 deg C, and immersion for 15 minutes was necessary for sterilisation purposes. Bolwell’s dipper was similar in construction but used steel plate for the outside of the firebox rather than the bricks used by Detlaff. The 100 mm gap around the dipping vat inside it allowed for effective heating. Again, the chimney was positioned to the rear so it did not interfere in loading and unloading the dipper. Matheson estimated the cost of paraffin at about 5 cents per super (but did not estimate labour costs).

Wax dippers have been variously heated by wood fire, by home heating oil, by LPG, by electricity – by any means that could efficiently (and cheaply) create the high temperatures needed, especially when considering sterilisation. The recommended temperatures for sterilisation were remarkably consistent through the years, until the 160 deg C and 10 min was confirmed by Dr Mark Goodwin in 1998. Beekeepers have used several grades of paraffin wax (generally described by its melting point), with no mention of any having any particular advantage. Micro-crystalline wax is sometimes added, giving the resulting mix a higher (and somewhat safer) boiling/flash point.

The use of hot paraffin wax dipping for AFB sterilisation has always been a “discretionary” activity. In earlier years a Department of Agriculture (later MAF) advisor would make a case-by-case decision on whether the operator was capable and willing to meet the time and temperature requirements. That is still the case, with the decision now resting with the AFB Pest Management Plan’s Management Agency. The process must be included in a Disease Elimination Conformity Agreement (DECA).

Wax dipping of boxes for preservation is now wide-spread through New Zealand. The use for AFB sterilisation is restricted but still significant and valuable as a tool for the elimination of AFB, the goal of the AFB PMP.

Summary: Use of Paraffin Wax Dippers

1930 Bates use of paraffin wax dipping described by W.B. “Billy” Bray
https://beekeeping.nz/NZBDA/Paraffin_Wax_Dipping/1930_03_Wax_dip_for_preservative.pdf
Preservation
Dipper not described
Importance of dry wood

1939 dipping in general described by D.S. Robinson
https://beekeeping.nz/NZBDA/Paraffin_Wax_Dipping/1939_01_Journal_Ag_Wax_dipping.pdf
Preservation only described
Wood-fired vat type dipper
Paraffin costs 3 ½ d per lb and a box takes just under 1 lb, so cost is 3 ½ d per full-depth box
Tank, 4 ft (l) x 3 ft (w) x 1 ft (h) (4-6 in deep wax)
15 – 20 sec dip
Paint before dipping or several years after.
Temperature: “when wax is boiling”

1953 dipping in general described by Sid Line
https://beekeeping.nz/NZBDA/Paraffin_Wax_Dipping/1953_09_Journal_Ag_Wax_dipping.pdf
Preservation and sterilisation
Wood-fired vat type dipper
Discussion on appearance/use of wood stains, with stain or creosote applied, allowed to dry, then dipped.
Photo of 4 ft square, 2 ft deep unit (but only 4 in deep wax)
2 to 3 supers at a time, about 10 sec per side
316 deg F for sterilisation (white smoke on surface) for 10 minutes
New super absorbs ½ lb wax, re-dipping less than that
Can be later painted with aluminium paint (bitumen-based)

1964 Russell Berry’s device, described by Sid Line
https://beekeeping.nz/NZBDA/Paraffin_Wax_Dipping/1964_10_Wax_dipping.pdf
Preservation and sterilisation
Wood-fired trough type dipper
Water-based stain and allow it to dry before dipping. Suggests Condy’s Crystals (potassium permanganate).
Advantage of permanent firebox, portability
Tubular steel rods (above and below) hold boxes under wax as they are pushed through
300 – 400 deg F (suggestion of smoke vapour on wax surface)
100 supers per hour (est 36 sec immersion)
6 ft 9 in long (not including 8 ft long drip tray), 5 ft length of wax surface, 2 ft deep at deepest point
Can use creosote or old oil before dipping

1968 Fred Bartrum’s device, described by Vince Cook
https://beekeeping.nz/NZBDA/Paraffin_Wax_Dipping/1968_01_Wax_dipping.pdf
Preservation and sterilisation
Heating oil-fired trough type dipper
Heated with home heating oil, with 14 x 2 in tubes to convey the heat through the wax
316 deg F suitable for both preservation and sterilisation, 2 mins to preserve, 10 min to sterilise
25 supers per hour, est cost 6 cents per box including labour

1978 Norm Findlay’s device, described by Murray Reid and Andrew Matheson
https://beekeeping.nz/NZBDA/Paraffin_Wax_Dipping/1978_06_Wax_dipping.pdf
Wood-fired vat type dipper, chimney through middle
Vat with woodfired firebox below, short chimney up through the middle
Will hold 2 full-depth supers (lift over the chimney)
3 packets of wax at $13 to fill from empty, 1 ½ hours to heat from cold
160 deg C the target, so wax will “really bubbles and boils up around the boxes”
4-5 mins or up to 7 min for preservative, 10 minutes for sterilisation
2 coats of water-based paint shortly after removing from the wax

1980 Keith Detlaff’s device and Rex Bolwell’s device, described by Andrew Matheson
https://beekeeping.nz/NZBDA/Paraffin_Wax_Dipping/1980_12_Wax_dipping.pdf
Both vat type dipper with chimney coming from back of unit
Both are vats with wood fire in firebox below, but with chimney coming up from the back
Detlaff’s: 85-90 kg of wax (which costs $1 per kg). 160 deg C, 5 mins for preservation, 15 min for sterilisation. 2 coats of acrylic paint while hot.
Bolwell’s: Depth for 2 supers means it holds a lot of wax, est of 5 cents per super to dip

Other related references:

Dept of Agic description of acceptable AFB practices at the time
https://www.beekeeping.nz/NZBDA/timeline/1928_11_Foulbrood.pdf

‘Shook swarms’ considered ineffective for AFB control. Dipping mentioned but not in detail
https://www.beekeeping.nz/NZBDA/NZBkpr/1950_08_NZBkpr.pdf#page=16

Dept of Agric changes policy to disallow ‘shook swarms’, refers to sterilisation use of paraffin wax dipping
https://www.beekeeping.nz/NZBDA/timeline/1950_11_Dept_Ag_AFB_policy.pdf

Robert Davidson describes scorching methods, questions dipping for sterilisation
https://www.beekeeping.nz/NZBDA/timeline/1950_05_Davidson_on_AFB.pdf