Invert without a mess

Celebrating the 80s - 50th Celebration of Chem 13 News

To invert a test tube (or bottle, etc.) filled with water into a beaker of water, place a piece of filter paper on top of the brim-full tube, wait until the water has soaked into the paper enough to hold it on, then invert the tube and insert it into the beaker at an angle slightly off-vertical. Once the tube mouth is under water, the paper will float off.

an illustration of two test tubes completely filled with water – one has a filter paper on top – pictured concave at the top. Then test tube with the filter paper is shown inverted into a beaker of water. The filter paper is still concave at the top of the test tube

Method to invert a water-filled test tube into a beaker of water

Surface tension and atmospheric pressure keep the paper in place without any need to hold it with your finger, but work over a sink just in case. Filter paper works well, but almost any kind of paper can be used. Beside being less messy, this technique has other advantages over using your thumb. It is especially suited to working in cramped quarters, or with corrosive solutions or with vessels that have an opening bigger than your thumb.

(Thanks to Lew Brubacher, former editor of Chem 13 News).

    February 1989