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I recently tried some defoaming additives because I was having trouble with foaming while stripping barley malt mashes. I had previously used simethicon (silicon oil) with success but I was looking for a DIY defoamer, preferably made from grocery store ingredients. The test still I used was a continuous still made of laboratory glassware. This was a good opportunity for testing defoamers since I could see what was happening inside the pot and column. The still pot was a 2 liter glass flask in an 800 watt heating mantle. The column was a 500mm “thorn” column with the wash injection point 2/3 of the way up the column. The set-up is particularly prone to foaming due to its small volume. The still was warmed up and brought to a steady state with wash, fed by a digitally controlled stepper motor peristaltic pump. Each defoamer was mixed into a liter of wash with a blender-on-a-stick. A liter of wash with the test defoaming agent was run through the still. I observed how well it knocked down existing foam, and the new steady-state foam level. I measured how much of the column was blocked by foam as well as how full of foam the reboiler pot was. After the 1 liter test, the feed was switched back to wash with no defoamer until the still returned to steady state. Then the next test would begin. For silicon oil, I used “Five Star Defoamer 105”, 2 drops per liter. This is 1:100,000 dilution, or half the maximum recommended by the FDA. The other defoamers were various strengths and combinations of olive oil, butter and dishwashing liquid detergent. Results: BEST (No foam in column, surface of boiling Reboiler wash visible) 1 tsp olive oil or ½ tsp olive oil + 1 drop dishwashing liquid detergent (DWLD) OK (foam blocking 2” to 6 “of column) ½ tsp olive oil or 2 drops DWLD Ineffective (Reboiler full of foam, column full of foam) 1 tsp butter or 1:100,000 simethicon The olive oil, alone or with DWLD, was the clear winner. I was surprised at how poorly the simethicon performed since it is so effective at “knocking down” foam in an open mash tun. Adding DWLD to olive oil keeps the oil in suspension if the mixture is stirred up with a “blender-on-a-stick”.