Treatment for Varroa with Oxalic Acid usually takes place in mid winter when there is no brood.

The simple method is to open up the hive and dribble the oxalic acid onto the seams of bees

The issues with this method of treatment are that it takes place in cold weather and the bees are then covered in a liquid which might cause the bees to get too cold and perish.

One way around this method is to evaporate oxalic acid under the varroa floor such that the vapour circulates through the hive without getting the bees too wet.

Roger Hurn in Bronllys has developed a simple system for evaporating oxalic acid in this way. The method is to make a small copper tray to hold the oxalic acid. The Oxalic acid is then heated to boiling point by using a diesel car glow plug powered from a 12 volt car battery.

Here are some photos of the copper tray that is made from two short pieces of 10mm copper pipe and a peice of copper plate and soldered or brazed together to become water tight

Here is a video showing the vapouriser working