When using anti-foam, you are never going to get rid of all the foam no matter how much anti foam you use. The idea is to try and control the amount with the least amount of anti-foam as possible and makes sure that you don’t have a “fluff” up after switch that causes a foam over. By using the gamma level, you can determine approzimately how much foam you have by tracking the differences from the level at switch to after switching. This will show you the amount of foam that you had present at switch time. Normally (depending on types of crude and charge rates) you can have anywhere from 2 feet of foam to 10 feet of foam at switch time even with the full amount of anti-foam being injected. Remember some crudes are bad about foaming after switch.