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I am having a problem with the oxalic acid incompletelly vaporizing, as you can see in the attached photos. After 2 minutes with battery connected and then another minute or so left to continue vaporizing in the hive, what's left is a ring of fairly solid oxalic acid. I have tried this in observation and what I see happening is the oxalic acid crystals liquify, begin to boil, and then leave this incomplete residue.

I am using pure OA, purchased from a chemical supply company, and using the spoon doser that came with the vaporizer. It seems that 2 minutes, especially after being warmed up , is supposed to be enough according to instructions for OAV. I do not want to keep the vaporizer in place so long that it could possibly set fire to the hive.

Anyone have ideas what is my problem? Maybe I need to go to 3 minutes? At risk of burning my hive?
 

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I found problems when I left the 1/2 tsp as a clump in the center of the pan. I don't think the heat was able to get to the center of the pan overly well

It went a whole lot better when I made a loose rim near the edge where the heat band is. Make a thin layer in the center of the pan by pushing the OA crystals to the perimeter. It doesn't have to be fancy!
 

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I use a ProVap now, but that would happen to me with the Varrox as my battery started to weaken. I would sometimes have to leave it on for 3 to 3 1/2 minutes to get it fully vaporized. Yes, it made me nervous, but I did not start any fires. Monitor closely. I always had a quart of water with me when using the Varrox so I could quench the Varrox pan between hives. That quart of water could come in handy if you started a hive fire too I guess.
 

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More than likely you have corrosion on the connections where you can't see. It happened to me and I believe it was from quenching between hives. I got to where mine was open continuity from the positive to negative. After disassembling then cleaning, it works like it did on day one.

+1 on the tip about building the oa around the rim instead of the centre
 

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Right now,one hive consisting of two 10 frame deeps of an Ohio swarm of muttsutts.
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Actually the instructions say to attach it to the battery and leave it in the hive for 2-1/2 minutes, then disconnect the cables from the battery and leave the Varrox in for an additional 2 minutes. So maybe you shorted yourself if you only left it attached for only 2 minutes. Just a thought, as I only used mine four times so far and have very little experience with my Varrox. I didn't know about pushing the OA up around the perimeter until now but that sounds like sound advice and makes good sense. That would give more even heat all the way around.
 

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I have run into that from time to time. Make sure there are no clumps and battery or power source is fully charged. Don't think an extra 30 sec to a min is gonna burn bottom of box any worse
 

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For curiousity sake, do a test run outside the hive.

Place OAV in pan and spread to perimeter and start your timer and connect the leads. You'll readily find out if Varrox is operating properly in 2 1/2 mins.
 
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When I was using the pan type, I cleaned the burned wax and propolis after each burn and cleaned the OA residue after each session. Yours looks rather dirty to me.
Also,I would lengthen the time it was connected in shorter increments, possibly 15 seconds rather than jumping from 2 minutes to 3.

Good luck
Alex
 
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I had a lot of problems with variable performance using the Varrox with a battery.
The problem is that the power going into the pan varies with the square of the voltage, so small changes in voltage make big changes in power. Batteries tend to droop when discharging 10A for 2 minutes. They droop a lot more if you try to do that repeatedly.
I happened to scrounge a 12V regulated supply (12V +/- 0.05V) which produces very consistent results. It clears the pan of 2g OA in about 1 minute 40 Seconds. Since I have AC power, this works for me. It probably wouldn't work for most people.
Your problem is normal. You need more time, or a stiffer voltage source. If you have a volt meter, put it across the terminals of your battery while you are waiting. You will see what is happening.
 

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I found that absorbed moisture in the OA seems to affect the boil off of the water of hydration. Bubbling up in cold conditions seems to produce an elevated crust that has reduced thermal contact with the tray and sublimation is delayed for a period of time before the crust falls into contact with the pan and then recommences sublimation.
 

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Good points! Thanks for the thoughts about batteries.
Also about a battery for running the Varrox. Somewhere,I also read where they suggest a battery with so many Amp hours as a minimum. Right off my head,I am thinking they suggest at least a 40 amp hour, 12 volt battery. I am sure it is in their directions so check it out or go to their website and see what you find. So, if you should have to get a new battery for it,I suggest using a deep cycle battery like they use for marine and camper use as they will hold up better to more recharging over a regular car or truck battery.
 

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All of Randy Oliver's crew tried vaporizing oxalic acid and wondered why anybody would bother with it. The dribble is cheap, safe, simple, effective when there is a brood break, and a lot less effort. 2 people can apply OAD to 400 hives in a day quite easily.
 

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All of Randy Oliver's crew tried vaporizing oxalic acid and wondered why anybody would bother with it. The dribble is cheap, safe, simple, effective when there is a brood break, and a lot less effort. 2 people can apply OAD to 400 hives in a day quite easily.
Never tried the dribble, as it looks like it requires more skill, and also it is a bit rougher on the bees.
I might try it at some point, but right now, I am OK with the vaporizer.
You can vape your bees every day for a month and they won't mind it. (not recommending that).

I realize if I had 200 hives to do, the vaporizer may not work very well, at least not the little frying pan version.
It takes me about 5 minutes per hive. That would be about 100 hives per day, if I wanted to work that hard. I suspect with the provap, I could get it down to 2 or 3 minutes, though I have never tried it. I spend my waiting time working in the garden or cleaning up the mess in my bee yard, so it isn't time entirely wasted.

After a while, you learn there isn't any point to sealing anything but the lower entrance, and that can be done quickly.
 

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What MGolden said, run it in the open air so you can see exactly how much time it needs and when you can turn it off to finish. FWIW, I run a wand on 120 AC and it takes about 5 1/2 minutes to complete, then I turn it off and wait another minute or two to be sure it is finished. I also spread the oav crystals out in the pan. I have screen bottom boards and made a 1/4 inch luan plywood bottom to replace the plastic board during treatment. It has a piece of disposable aluminum pie pan stapled to the center to act as a heat shield under the wand. Never a hint of anything getting too hot/scorched.
 
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