# Residue from oxalic acid vaporization?



## Phoebee (Jan 29, 2014)

I'm fairly new to using oxalic acid. I bought a vaporizer last year and zapped one hive with it in January 2016, with apparently excellent results. The hive thrived and had an extremely low mite drop all year.

However, I worried that this vaporizer gets too hot. Like most, it was unregulated, and the instructions warned that it might melt the aluminum cup if left on too long. My one use produced a lot of black residue in the cup. I had expected it to vaporize away cleanly if the OA were pure.

This summer I rigged a battery box and temperature controller for it, in an attempt to hold the unit down below the OA decomposition temperature. I got to try it out on our mentee's hives today. 

On the first hive I had the controller set to 320 F, knowing the temperature overshoot would take it up into the 360-370 F range. The first hive we tried it on was already a deadout, so it made a test where we could do no harm. The system failed to vaporize all the powder, so we ran it a couple more times at higher temperature settings, finally setting 360. There was still some white powder left.

For the second test, on a live hive, I left the unit set at 360. We used 2 grams, and the temperature overshot to about 410 F, into the decomposition range but probably a lot less temperature than the unregulated units produce.

This second test produced a black, soupy residue.

The OA we were using was from Brushy Mountain's properly labeled 30 gram kit, both my treatment last year and today's treatment.

I also notice some YouTube videos of OAV treatment produce black or grey residue.

I'd like to compare results to other OAV users. How many of you get black residue, how many of you get complete vaporization with little residue, and what source of OA are you using?


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## Fivej (Apr 4, 2016)

I have a Varrox wand. The bottom of the pan is stained black, but no residue at all. I use Savogran Wood Bleach. I suspect the problem is your wand, not the oxalic acid you are using. J


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## GarrickG (Nov 29, 2014)

I use a varrox. I've had wax (and occasional bee) get into the pan and leave a black gooey residue... I've since installed slatted racks and get no wax in the pan.


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## Lburou (May 13, 2012)

GarrickG said:


> I use a varrox. I've had wax (and occasional bee) get into the pan and leave a black gooey residue...


X2


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## Phoebee (Jan 29, 2014)

GarrickG said:


> I use a varrox. I've had wax (and occasional bee) get into the pan and leave a black gooey residue... I've since installed slatted racks and get no wax in the pan.


Melted wax ... I had not thought about that but it makes sense. That could be why it was soupy.


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## crofter (May 5, 2011)

Phoebee said:


> Melted wax ... I had not thought about that but it makes sense. That could be why it was soupy.


Yep, absolutely: wax and propolis and the odd bee and you get a bubbling black charge. The oxalic acid will sublimate out of it but leaves a deposit that is a bit difficult to scrape out. I often dont bother scraping but I think it acts as a bit of a refractory to sublimating the next charge. 

You can heat and drive off a number of charges from a clean pan (outside the hive) and will only see a thin grey appearance.


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## sterling (Nov 14, 2013)

Dip in water quickly and wipe with a cloth while it is still warm to clean the pan.


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## costigaj (Oct 28, 2015)

With my wand, an OXAVAP, I need an extra 60 seconds added to the recommended burn time to get a complete burn. Otherwise I get a black lump. I clean mine with steel wool and a wooden stick


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## mgolden (Oct 26, 2011)

I was getting the black lump at times after the treatment. I now spread the 1/2 tsp around a bit in the pan so it is no longer a clump. Vaporization goes a lot better.


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## frogpondwarrior (Aug 2, 2016)

Once in a while I get a small black clump. It usually happens because my wand was not completely dry before use or I cut my time short. One time it was left in the hive too long and now there is this lump distortion in my plastic tray of a screened bottom board.
Also, noticed that although using the exact same measurement each time it varies from hive to hive the burn off time. Does anyone know if this is due to hive moisture content, density or because occasionally a bee jumps in the wand and turns into a crispy critter.


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## sterling (Nov 14, 2013)

costigaj said:


> With my wand, an OXAVAP, I need an extra 60 seconds added to the recommended burn time to get a complete burn. Otherwise I get a black lump. I clean mine with steel wool and a wooden stick


that sounds more like a battery problem. I use a jumper box and run two at a time and they vaporize fine in 
2 1/2 minutes until the jumper starts to get weak.


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## snl (Nov 20, 2009)

Some of users issues center around how the OA is placed in the pan. Whether is spread around or just lumped in the center. On the Varrox I tend to move the OA to edges as where that's where the heat begins. On the others, I distribute it evenly in the pan. 
I've found that with these easy tips and a good battery, I have no residue.


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## Phoebee (Jan 29, 2014)

I ran five hives this weekend, and they went much better. 

I did get some crispy bees a couple of times. I think the worst case is a deadout ... dead bees dropped into the pan. That hive still had a full feeder on top and we think it was killed by condensation.

The rest were out flying today and seem to have suffered no ill effects.

I figured out to put the OA into the pan and then press it down to a uniform layer. If I left it fluffed up or in a pile, it did not vaporize fully, but left a lacy white mass behind.

Its not a battery problem ... my vaporizer is temperature controlled. Those of you with unregulated units have no idea how hot they're getting. Way above the decomposition temperature, I'm sure.


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## snl (Nov 20, 2009)

Phoebee said:


> Its not a battery problem ... my vaporizer is temperature controlled. Those of you with unregulated units have no idea how hot they're getting. Way above the decomposition temperature, I'm sure.


A good vaporizer does not need a temperature controller as they are designed and tested to vaporize OA at the correct temperature.


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## Phoebee (Jan 29, 2014)

snl said:


> A good vaporizer does not need a temperature controller as they are designed and tested to vaporize OA at the correct temperature.


Well, say what you will about the quality, but the Brushy Mountain model I have warns you not to leave it turned on more than about 2 minutes, because it may melt down. The melting point of aluminum is WAY above the decomposition temperature of OA. So I feel justified in adding a digital temperature controller.


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## Mike Gillmore (Feb 25, 2006)

snl said:


> ....A good vaporizer ...


Key words. A Varrox will not melt down if left on over 2 minutes, or 3 minutes ...

Works as designed every time.


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## Arnie (Jan 30, 2014)

Phoebee said:


> Well, say what you will about the quality, but the Brushy Mountain model I have warns you not to leave it turned on more than about 2 minutes, because it may melt down. The melting point of aluminum is WAY above the decomposition temperature of OA. So I feel justified in adding a digital temperature controller.


Brushy Mt. sells the Varrocleaner. I have 2 of those and I can personally attest to the fact that it will not melt. I once left one of them on WAY past the three minute mark and when I pulled it out of the hive about an inch of the metal shaft next to the aluminum pan was glowing red hot. 
The unit still works, although I have to give it an extra 14 seconds above the 2 minutes thirty second time to vaporize fully. 

So proceed without fear.


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## Mike Gillmore (Feb 25, 2006)

I wonder why Brushy Mountain would include that kind of a warning with their product.


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## snl (Nov 20, 2009)

Mike Gillmore said:


> I wonder why Brushy Mountain would include that kind of a warning with their product.


I believe they (like me) had a user get distracted and leave it in the hive way longer than 2.5 minutes (like 10) then come back to a melted mess...


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## mgstei1 (Jan 11, 2014)

I use a DIY 2.5 minute on delay timer feeding a 50A automotive relay going to a buss powered by a 35ah wheelchair deep cycle battery all enclosed in a carpenter box.
I can run 2-3 wands off the buss and attach my Kelly wand with a temp control and timer directly to battery posts. Its slower but its self controlling.
Started using a DIY band heater driven by 120vac and drill a 3/8" hole in bottom board rim(3/4"x3/4" )on long side and it treats in 50secs.
Jury still out on it but works great so far. Drawback is toting a generator or attaching an inverter to the battery.Bigger box needed.
Biggest time saver is using OA 1 gram tabs to charge the wands and the band style.
Ive never killed a queen or melted frame comb but have toasted a few workers and melted bridge comb on solid BB. I now have all SBBs which lessens the chance of toast.


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## mgstei1 (Jan 11, 2014)

Heres the box and also the schematic.
View attachment 29660
View attachment 29661
View attachment 29660
View attachment 29661


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## sc-bee (May 10, 2005)

snl said:


> I believe they (like me) had a user get distracted and leave it in the hive way longer than 2.5 minutes (like 10) then come back to a melted mess...


I have a varrox and wanted to purchase another vaporizer to run more than one unit at a time.Yep, I bought a beekeeper shop made as the second vapoerizer So of course the varrox is a far more superior unit and heats quicker than the home made aluminum block. How long can the varrox run without worrying about overheating and damaging the unit while I wait on the home made vaporizer to catch up? The home made takes about 1 1/2 to 2-mins longer from what I see. 

And has anyone actually caught a bottom board on fire with a vaporizer or is that just a tale? Of course my luck.. I would be the first


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## snl (Nov 20, 2009)

sc-bee said:


> How long can the varrox run without worrying about overheating and damaging the unit while I wait on the home made vaporizer to catch up?


I'm not really sure as I'm not purposely run one long enough to overheat and damage the unit. I know it is still ok at 5 minutes... hot as hades, but ok.


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## Nabber86 (Apr 15, 2009)

Has anyone ever managed to actually melt the aluminum in a vaporizer? Seems like it would be really hard to do even if you tried.


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## snl (Nov 20, 2009)

Nabber86 said:


> Has anyone ever managed to actually melt the aluminum in a vaporizer? Seems like it would be really hard to do even if you tried.


I did have on come back to me that was melted........ the owner could not remember how long he had left it unattended, but it was a while....


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## DanielD (Jul 21, 2012)

Here's a thread with a vaporizer failure. The photo isn't available in the thread anymore.

http://www.beesource.com/forums/showthread.php?317578-Fire-in-the-hive&highlight=vaporizer+burned


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