The amount of time that parts spend in ultrasonic cleaners, along with the type of detergent used and its temperature, determine how clean they’ll be when removed.
Obviously, not all parts need to be cleaned to the same degree—it depends on what you’re going to do with them later.
Whether you’re using ultra sonic cleaning to restore the luster on treasured heirlooms, or cleaning parts to remove oil, grease, or wax, there are a number of tests you can do to fine-tune your cleaning process.
Here are some tests you can do to check how clean your parts are after ultrasonic cleaning:
Visual – The simplest test is a visual test. When the pieces are done being cleaned, do they look good to you? Do they shine, sparkle, and have luster? Sometimes, this is the only test you need to determine if your parts are clean enough, particularly if you’re working with family heirlooms or personal belongs, such as silver sets, china, crystal, or jewelry. A test doesn’t have to be complicated to prove results.
White glove – Another simple test is the white-glove test, and the procedure is exactly what it sounds like—wiping down the parts with a white-gloved hand after they have been in ultra sonic cleaners. If the glove is clean, try washing the next group of parts for a little less time. You can reduce your cleaning cycle in this way, and save time.
Tape Lift-off – This test requires a little more scrutiny to make sure parts have been cleaned properly in ultra sonic cleaners. After the part has dried, wrap the part in clear tape (packing tape works great) and press it down hard against the surface with your hand. Then, pull the tape back off, being careful not to touch the sticky side with your fingers. Examine the tape by holding it up to light, and look for metal shavings, dirt, oil, or grease. If any particles are found, you may need to do additional ultra sonic cleaning based on the size and quantity of contaminants.
Atomized water – Thin films of oil and grease are difficult to detect on a surface. One of the easier tests to perform when looking for light coatings of oil or grease is an atomizer test. In this test, distilled water from a spray bottle is misted onto the part, and the water film is examined. If the part is completely clean, the water will spread evenly across the part. Where oil or grease is present, the water will either bead up or separate.
Florescence and Solvent Rewashing – If a part must be completely free of oils, greases, and waxes, or completely particle-free, it may be necessary to perform a more in-depth test like florescence or solvent rewashing. Because most oil films “fluoresce,” shining a UV-light on the part in a darkened room will show any oil or grease present on the part.
To look for fine particles that were not detected by the tape lift-off method, cleaning the part a second time using a solvent like isopropyl alcohol or mineral spirits, and capturing the runoff in a clean tray for examination, will reveal any particle contamination left behind. Tests this involved are not usually necessary, but they are available and used in certain circumstances.
Cleanliness is application-specific, and over-cleaning parts in ultra sonic cleaners will waste time and cost you money in unnecessary power usage. You must make sure the parts are clean enough to perform successfully in the final product or next process step; anything beyond that is icing on the cake.