With the Mini and especially with the Micro and Ultra Micro line of phantoms, it can be difficult to always replace all the air in the phantom with liquid. Bubbles large enough to be visible to the unaided eye will likely be large in comparison with structures within the phantom. A reason for this difficulty is the surface tension of water makes it hard to flow easily into and then through small passages. Small (less than 1-2 mm) bubbles tend to stick to surfaces inside the phantom much more so than do larger bubbles.For any Data Spectrum Phantom, NEVER use any kind of alcohol or solvent to fill them. Use of alcohol or solvents of any kind is very likely to damage your methyl methacrylate (MMA) or polymethyl methacrylate (PMMA) phantom. Because the gaps between the plates (of the Defrise phantoms) or holes (in the Hotspot or cold rods in other phantoms) phantoms are small, you may encounter some small bubbles that adhere to the inserts and/or cylinder surfaces. You might find it helps to use a thinner or wetting agent (surfactant) of some kind that will reduce the tendency of small bubbles to adhere to the wall and gaps. A few drops of common dish washing detergent (that is, the kind that is used with automatic dishwashing machines) may be used to minimize this effect. For example, a solution of 1 mL dish washing detergent, (such as Cascade gel) added to 200 mL water may be tried. Also you may try 2 or 3 drops of liquid dish soap such as Ivory or Joy) added to 100 mL of water. This latter solution may produce too many bubbles, if the solution is stirred too vigorously. Be careful not to mix the solution so vigorously that soap bubbles form. Some hand soaps contain a surfactant and a few drops of these kinds of soap, added to 100 mL of water may also be tried. Avoid alcohols, solvents, and even any soaps or detergents that may contain alcohol or solvents of any kind.A trick to help determine where liquid has gone to in your phantom is to add a visibly high concentration of food coloring. Red food coloring works well.Be certain with some of the DSC phantoms to fill the phantom with it in the proper orientation. Also, some older style phantoms must be filled with a syringe under the phantom injecting upward, rather than downward into the phantom. Your User’s Manual for your particular phantom will show and explain to you exactly how to fill your phantom. Again, older manuals might state that it is alright to use alcohol in phantoms, but this is no longer the case.