UPDATE to OAV presentation - important

[Charlie Garrott]

I discovered that the 12-minute time for my oxalic acid heater wand is excessive and harmful to bees. The wand should vaporize all the oxalic acid within 3 minutes. See comments below:

Michael Jaross via groups.io <michaeljaross=gmai...@groups.io>

Thu, Sep 11, 2:55 PM (19 hours ago)

to mtbakerbees

The burn time for a new JB200 pan-style OA vaporizer from Heilyzer in Victoria BC is 60 seconds. After long use the heating element builds up resistance and burn time increases slowly. When it gets to 90 seconds I change out the element, an easy to source diesel engine glow plug.  I got 10 years of use out of my oldest pan burner before I replaced the glow plug. It still worked fine, but burn time was over 90 seconds and I wanted to return to 60 seconds.

 

I used that particular brand of vaporizer wand for about 15 years with good success. I still have a couple in my OAV tool box as backup in case my newer digital vaporizer fails. There's not much to go wrong with this particular burner model. The heat source is robust and rugged, designed to operate inside a diesel engine. As with any electric/electronic tool exposed to corrosive fumes, the electrical connections are the weak points and need to be cleaned and reset annually. That's one of my chores at the beginning of OAV season in the fall, along with a "test burn" outside the hive to establish an accurate burn time by observing how long it takes to vaporize all the OA powder.  

 

During the time I've been treating for mites with vaporized OA, I've gone through a lot of the literature and studies. There isn't really much on practical applications, (you can't patent OA and the market is limited), but a general consensus about best practices has been formed over the nearly 35 years that OAV has been in use. When it comes to "burn time," the time a vaporizer is energized and heating up, the shorter the better. Long heating times not only traumatize the bees

but OA particles closer to the heat source get too hot for too long and produce harmful byproducts of OA. 

 

The longest heat time that seems to be acceptable is 2-3 minutes with pan vaporizers. As mentioned, the pan vaporizer I used for many years had a burn time of 60-90 seconds by which time all the OA had vaporized and the pan was empty. Newer digital vaporizers are even faster than that. I haven't timed the burn on my newer digital vaporizer, but it's definitely under a minute. 

 

The whole concept is to vaporize the OA dose as quickly as possible without generating so much heat that it damages the hive materials and bees. You want the vapor to be produced quickly so it rises with its initial heat and suffuses the entire volume of the hive. The longer the burn time the more the colony reacts, resulting in more casualties.The bees react to the burner itself because it's a clear, physical target, not so much to the vapor as it's ubiquitous. There's no "there" there. Minor bee casualties are unavoidable with pan burners operating through the hive's front entrance, a small price for a huge benefit. Digital burners, operating more or less clandestinely through tiny hole in the back of the hive, produce virtually no casualties.

 

The trick to getting a fast pan-vaporizer burn and getting the vaporizer out of the hive quickly is the mass of the aluminum pan itself. The less mass, the quicker it heats up if the heating element is efficient. There are many OA vaporizers on the market and quite a few of them are not very well built. It takes a good machinist and equipment to turn out a truly thin-walled vaporizer pan. Here's the JB200 pan looks like: 

As can be seen, the walls and floor of the pan are about 1/16" thick and the only significant mass is where the heating element, the glow plug, rests inside the pan and that volume is mostly hollow. There's another rectangular aluminum block separate from the pan, but that is just to secure the heating element in place, it's not directly heated and doesn't influence the rate of burn. 

 

I am not making an advertisement for this particular vaporizer, just using it as an illustration to show how a rapid, controlled burn can be achieved. As I noted, many commercial burners are much thicker, use inefficient heat sources and have excessive burn times. This is often true for homemade OA burners where machining skill and tools are often limited. 

 

I suppose we should start another thread with its own subject line for these comments about OAV equipment. It's an interesting issue, complicated by an unregulated market and a sad shortage of practical, reliable information about how OAV works best. I'm glad we are trading information and asking questions on the forum here.