Ultrasonic Dishwasher? – Probably Not

A reader has asked about the possibility of using ultrasonics to wash dishes.

He writes – – – “Ultrasonic cleaning in a dishwashing application is something that I am currently interested in. Having read some of your other blog posts which mention sequential use of turbulation in the liquid to supplement the ultrasonics, I was wondering whether this is an application where you found or think that this would be necessary? Having experimented on a small scale on this topic, I certainly found that trying to remove a thick layer of contaminant with ultrasonics alone was very difficult or impossible.”

In an earlier blog I expounded on why I feel dishwashers are a bit of a waste compared to hand washing. I also revealed in another blog the fact that using ultrasonics to wash dishes is probably not feasible but neglected to provide details other than the water consumption required to provide a device that would be able to immerse the dishes as required for ultrasonic cleaning.

The reader has hit the nail on the head when he mentions the issue of removing thick buildups of food using ultrasonic cleaning alone. I addressed this issue in a preceding blog as well but it is worth going into a little further. First, let’s look at the kinds of things that one might find on dirty dishes. One classification, liquids, don’t often leave a very thick buildup once drained. Also, most liquids (water-based liquids) are, of course, water soluble. Residues of fruit juice, wine, soda, beer, milk (?), and other beverages are well within the realm of ultrasonic cleaning because they are very thin films. However, food residue left on dirty dishes after a meal is not what I would call a “thin” buildup of contaminant. Usually there are scraps of meat, gravy, vegetable residue, sticky gooey stuff that just can’t be removed using ultrasonics alone. And the longer these residues are left on the plate, the more they dry out making removal even more difficult.

Not being able to remove thick buildups of food residue, therefore, is a major stumbling block in the way of using ultrasonics to clean the typical overall range of dishes although it might be suitable for glassware and other lightly soiled pieces. It is true that using turbulation, agitation or some other means of providing additional mechanical scrubbing would probably render most residues otherwise resistant to ultrasonic cleaning removable . . . . . but then we would be right back to the standard dishwasher which, primarily, uses spray technology along with chemistry to clean the entire range of dishes effectively.

In summary, there are several reasons why ultrasonic dishwashers are probably not in our future –

• The need to immerse items to be cleaned in a liquid uses much more water than spray technology. A typical home dishwasher fills and drains 3 times using only a few gallons of water per fill. Filling and draining the entire cavity of a dishwasher would require more on the order of 150 gallons.
• The inability of ultrasonics to remove dried-on residues of food like gravy, spaghetti sauce and mashed potatoes.
• Cost – Ultrasonic technology has not yet advanced to the point that it can compete on a price basis with a typical home dishwasher which sells for from $300 to $1,200. An ultrasonic cleaner with the same volume as a dishwasher (approx. 50 gallons) would be priced at several thousand dollars or more even before customization for dishwashing.

In summary, having traveled this road several times before in my 45 year career in ultrasonic cleaning, my guess is that we will be washing dishes the same way we do today at least for the rest of my lifetime. Despite the big “carrot” out there, I don’t think the challenge can be met, at least with ultrasonic cleaning technology as we know it today.

– FJF –