Oxalic Acid Not Vaporizing

I’m currently treating my hive with Oxalic Acid vaporization to knock down the varroa mite counts which are pretty high. I tried to lay the vaporizer on a piece of plywood and put the vaporizer and plywood into the corflute slot to keep the fumes inside the hive. They fit and there is space between the vaporizer and the screened bottom board. However, the Oxalic acid (OA) won’t vaporize. It just pops out of the vaporizer tray onto the plywood. But, when I do a test with the vaporizer on the plywood out in the open, it vaporizes just fine. What am I missing here? Is there some sort of reaction the OA is having with the screened bottom board? Is it not vaporizing due to a lack of oxygen? I am plugging the opening with towels.

Alternatively, I could put the vaporizer directly into the hive opening, but I’m concerned about burning bees. Does anyone have experience doing it this way? It seems the more common way to do the vaporization, but I’d like to minimize the risk to the bees if possible.

I too worried about burning bees. You could smoke the bees to move them away from the OA wand and then put the wand in the entrance. I put mine in the entrance because that is the most direct way of treating them in my hive.

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I do it that way all the time, except I use a doubled piece of roof flashing in the slider slot. For my traditional Langs, I have solid floors, so I just slowly push the wand in through the entrance. It doesn’t seem to burn bees, but I use a slatted rack which gives them a bit more space, and avoids wax building up near the hive floor.

It sounds to me like your wand has a loose electrical connection somewhere. You might want to check the wires and make sure the connection to your power supply is secure. :wink:

If you are actually describing the OA exploding out of the wand, you could try just filling half of the reservoir, so that it is less likely to form a gas pocket under the OA. :blush:

Do you do this with your flow hive screened bottom board? They’re metal and I’m concerned that the OA wand would heat up the entire screen, making it too hot for the bees. I would assume that they would move up onto frames, but want to know for sure, and before I kill a ton of bees.

I use Dawns method and the fact is the iron gets hot but it’s also not on wood to burn. The bees move up in the hive during a treatment so they move away from the heat and the roof flashing cools pretty fast.

The heat transfer to a mesh screen is minimal. The heat will be ‘soaked up’ by the mesh. and so the temperature will actually become less. If the wand is on a cool surface the OA won’t heat up enough to vaporize and available oxygen is not part of the equation, I would be looking for a bad electrical connection or a loss of heat as the issue. Hope that explains it.

Perhaps a bit more clarification is needed. I’m still concerned.

Is that info about the heat generally true, or true of the metal the screened bottom board is made of? I think it’s stainless steel, and seems solid, not mesh like. I have the flow hive 2 in case that makes a difference.

I absolutely believe that it is generally true, and your problem is not contact with the mesh.

As I stated above, I put an aluminum roofing flashing layer into the slot in place of the slider. If heat transfer was a problem, the flashing would cause it for sure. The mass of metal would conduct the heat away very fast. After all, most pots and pans are made of aluminum because it conducts heat very well. If it was a problem, my Varrox would never work, but it it always works very well. Honestly. Truly. Never had a failure, cross my heart.

If your wand touches the mesh, the metal mass is likely much less than my heavy gauge flashing. I doubt that is the problem. Either you have gas pockets in the crucible, or you have an electrical problem. Without seeing photos, it is hard to tell. Any chance you could post some of the problem, and what you see on your plywood slider? Perhaps that would help narrow it down. :face_with_monocle:

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Ok I can definitely take some photos! I’m out of town for the weekend but need to do another treatment when I return, so will take them then. Thanks!

Dawn has worded it exactly right. Put simply, if the OX is not heating to a vapor then either your battery, or power source needs recharging or there is a faulty connection in the circuit of the wiring.


https://wn.nr/DVjTxA I came upon this today for the Chance to win the latest greatest varroa OA vaporizer.

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Awesome thank you so much!

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Ok I think the problem is gas pockets. i got another vaporizer to rule out the possibility of electrical issues and I’m still seeing the exploding of the OA, though this time not as much. This did partially vaporize as I saw the vapors (didn’t plug up the tray entrance all that well) whereas before it was hardly vaporizing at all.

What can I do about gas pockets? Put only 1/4 tsp at a time and treat two days in a row? (I have 2 boxes)


Hey Desiree, By trying another vaporizer it is just making me think of a faulty power supply that simply can’t supply the amps needed to heat the OA sufficiently fast enough. It is the only common denominator. I’m no expert in any way about the vaporizers as we don’t have a need for them here - yet. But I do know about heating and I have to stand by my previous advice, but over to @Dawn_SD to see if she agrees with me or has other advice as to what is causing your problem.
Cheers, and keep us updated

Well, you have certainly worked hard on this! The photo helps, thank you. I have never seen OA looking like that. I wonder if it could be your power supply? If the voltage is too high, the iron would get too hot and might cause such a problem. If you are using 24V rather than 12V, that would be a problem. Also, some jump starters generate 14V rather than 12V - that would be much less of a problem, but I don’t remember what you are using.

One other thought would be to try some different OA. I use Savogran Wood Bleach from Home Depot. It is plenty pure enough and has never exploded on me. :blush:

If you are going to go the half dose route, I would give the second dose immediately after the first. There really is no problem with closing the hive up for 20 mins or more while you get both doses in there.

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Ok I might try that. I’m using this jump starter. also I’m going to get roof flashing today and see if that works any better than my wood piece

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Thanks for the reminder about your power supply. I can’t see that as being the problem. I doubt that the flashing will solve it, but I am very curious to hear what you find. Just to help you, I bought a roll of 20" wide heavy duty aluminum flashing from Ace Hardware. I think it was under $10. It cuts easily with tin snips, and I just folded it in half to give it some strength.

If you are going to get flashing, you could consider adding some Wood Bleach to your cart at the same time! :smile:

Oh awesome thanks for the tip! I might actually just try putting the vaporizer in the entrance… see how that goes. The hive floor is actually pretty clean with little to no wax bits and few bees. Thanks for all your help on this everyone!


I attempted my first OA vaporization and have some concerns about how it went. Initially, I tried one of those lithium ion jump starters and mine would not provide any current because it had some sort of short circuit protection that shut it off. So, I used a regular 12v battery.

After putting my 1/2t dose in the crucible and making sure it had good contact with the metal, I connected and set my timer. I did see some fumes after about 1:30 and thought all was well but when I pulled the wand out after the cool down period, this is what it looked like:

Not sure how to get the rest of that to vaporize, seems like maybe the bottom of the crucible is getting much hotter than the rest and then a pocket forms preventing further thermal conduction to the remaining powder?


I am not quite sure what I am looking at in your photo. Did your crucible burn a hole in something? Or is that just the design of the wand? It doesn’t look like my Varrox at all! https://tinyurl.com/y2u6ppe2

The first couple of times I did an OA vaporization, I did it in the open air to watch and time it. It takes just over 5 minutes for 2 grams to vaporize in my Varrox crucible. I have not had any problems with it not vaporizing fully inside the hive. It works every time, flawlessly. Could you have a faulty vaporizer? :thinking:

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