Homemade External Heat Source Oxalic Acid Vaporizer


Background, Disclaimers and Cautions:

Beekeeping is part science and part art – open to experimentation to see what works, and thus the adage that get 5 beekeepers together and you will get 25 opinions on how to do something.

As this page about building a vaporizer, this is not the place to go into a dissertation on Varroa mite infestation and treatments, as there is a lot of information on the subject online. A quick summary of treatment highlights for perspective:

Varroa mites have become a big problem for beekeepers in recent years. In addition to the mite infestation, out of the 17 viruses that adversely affect bees, the mites are vectors for 11 of them. So monitoring and treating for mites is good beekeeping practice, not only for your own apiary, but to prevent the spreading of mites and diseases to neighboring colonies by drifting workers and drones.

Oxalic Acid Vaporization is one method of treatment available to beekeepers. It is a one time, “flash” treatment that is highly effective [95+%]. No harm has been found to bees, queen or brood with Oxalic Acid Vaporization treatment. However, a disadvantage of oxalic acid treatment is that it does not penetrate capped brood cells where the mites reproduce.

Brood-less colonies such as swarms or nucs can be treated once.

With brood, colonies can be treated in early spring or in the fall. Treating 3 to 4 times is necessary, approximately a week apart, as the Varroa mites’ reproduction cycle is 10 days.


  • You will be using open flame of a torch, and generating Oxalic Acid Vapors that should not be breathed in, and can irritate eyes, and skin. Read and follow cautions on labels, and use common sense.
  • Oxalic Acid Vaporization is NOT to be used during honey flow when supers are on, as honey thus exposed is not suitable for human consumption.

Advantages of an External Heat Source Oxalic Acid Vaporizer:

  • Uses your smoker torch for heat source
  • Thus, there NO danger of igniting bur wax comb, or marring any hive wood-ware
  • No large 12 V battery required
  • Very economical to make, only requires a hand drill and scissors, avoiding the expense of a commercial made electrical unit

Credit goes to our member and longtime beekeeper Bob Dolezal for this design. Pictures and text by John Mekis.

If you have multiple hives in you apiary, you can make about 3 of these and rotate using, cooling and filling the vaporizers.


Click on pictures in the table for full size images.



Air ChamberHome Depot – in the plumbing section where all the copper fittings are.

1/2"x8" Air Chamber

Commonly used as a water hammer arrestor.
Brass TubeAce Hardware – in the ‘hobby’ section;

K&S # 8131.
High Temp Rescue TapeAce Hardware – Silicone Rescue Tape, available in several colors
Ace Hardware – Conical neoprene stopper approx. 5/8” to 1/2” tapered diameter;
Consider purchasing spares;

[Picture is of a well-used, and wrapped stopper]
The Science Company – 7625 W Hampden Ave #14, Lakewood, CO 80227; Phone: (303) 777-3777

Basically NW corner of Wadsworth & US285, but somewhat hidden

Do not use commercial wood/rust oxalic acid cleaners, as they contain undesirable additives.

Around $10 for this size container, a lifetime supply or to share


  • Drill a hole in the neoprene stopper with a 15/64″ or ¼” drill bit
  • Insert brass tube all the way through stopper
  • Cut silicone high temperature tape; width to match stopper; length sufficient for 2-3 wraps
  • Wrap silicone tape, stretching as required. Test fit in air chamber opening
  • Done!

The well-used finished vaporizer:

Finished Vaporizer

Comment: I was tempted to use brass fittings instead of the stopper/silicone tape, but was talked out of it. That much metal acts as a heat sink and vaporization becomes problematic, not to mention substantial cost increase for those brass fittings.

Before use, you will need have these items on hand:

  • Your smoker torch
  • ¼ teaspoon measuring spoon
  • Timer [your smartphone]
  • Pliers
  • Wet rag
  • Respirator Mask [highly recommended – you DO NOT want to breathe the vapors!!!]
  • Entrance reducer [Optional]
  • Old metal can with some water [Optional – to quickly cool hot air chamber]
  • Gloves [Optional]
  • Duct tape [Optional]

Use and Application:

  • Have the above items on hand
  • It is recommended that min outside air temp is 40 deg F [5 C] or above
  • Fill Air Chamber with appropriate amount of Oxalic Acid. Recommended amounts are 1-1/8 grams per deep; that is approximately 1/4 level tea spoon
  • Seal hive entrance. I use a combination of entrance reducer and a wet rag, and push the brass tube trough the rag.
  • If necessary, close bottom board screen and tape inner cover notch.
  • Put on your respirator mask
  • Set timer for 2-1/2 minutes
  • Heat Air Chamber for 2.5 min; heat tip for a while, then sweep flame to near stopper. I’ve not found it necessary to heat brass tube.
  • Using pliers remove vaporizer assembly and put in can of water, or set on a nearby stone/ground to cool
  • Done!