Finding Cleaning Processes that Hide in Plain Sight: Ask “Why?” Ask “What’s That?”

To solve critical cleaning problems, be a preschooler. Ask: Why? Ask: What’s that? The source of the critical cleaning problems may be hiding in plain sight. A process might not be identified as cleaning; no one may think about it as cleaning. We were asked to improve a final aqueous cleaning process, one that everyone assumed was the most important cleaning step. It wasn’t! The true critical cleaning process, the “tipping point” step, was up-stream. It was a process no one thought was important, let alone that it was the critical cleaning process. 

The goal was to improve their aqueous in-line process, the last step prior to plating or other coating process. There was unacceptable coating quality on metal and plastic parts. The reject rate was high. Coating and plating quality were determined visually. Fortunately, the lead operations person – let’s call him Joe – was very observant and kept careful photographic records. Each picture was worth a thousand words; and there were hundreds of photos. You could see the fisheye and residue trapped under the coating. 

The aqueous in-line process was a thing of beauty. It looked like it ought to remove the soils; and, in most instances it worked. The facility was clean and well-maintained. Why were there seemingly random attacks of contamination? We continued with the preschooler approach to problem solving doing a step-by-step walk-through of the facility and the surrounding area and asking “why?” and “what’s that?” Because the manufacturing plant was middle of farmland we wondered if agricultural run-off was an issue. We run into water quality fluctuations all the time. Perhaps variations in water quality during the growing season was the source of the problem. However, perusing Joe’s careful records and photographs indicated no apparent correlation with season, rainfall, stage of growth of the crops. Pre-process water treatment was ok, although the client eventually decided to upgrade water quality. What that huge structure? The one big structure near the facility was a food processing plant; that could be a source of airborne contamination. Maybe. Airborne contamination from neighboring facilities can be a problem, we’ve seen the issue in industrial parks. However, suggesting that the client build a cleanroom and add a complex air filtration system would be costly and cumbersome. Right in the middle of the facility, there was an immense, open tank filled with what looked like slightly muddy water. “What’s that”? Joe explained that it was a buffing and polishing process where parts were immersed in hot water containing a dilute suspension of solid media in a solution of water containing surfactant. The parts were exposed to heat, agitation, rubbing with a polishing wheel. They were next submerged in clean water and agitated to remove the media and surfactant. This process sounded suspiciously like a cleaning and rinse process. The lightbulb appeared! This was not just a polishing process. It was a “fusion” process including washing and rinsing, a process where the non-chemical media was blended with an aqueous cleaning process. 

Were all parts exposed to this polishing step? No, some went straight to the in-line aqueous cleaning step. Why? It was deemed that less than half of the parts required polishing; it may also have depended on who wrote the specific process. Next, we looked to see if the rejects were associated with whether or not the parts were subjected to the polishing process. Joe checked the records; we looked at his photo gallery of poorly coated product. Sure enough, the polishing process was associated product that, after coating, had an extremely low level of surface flaws. Barbara wondered if the polishing step could be added for all product. We could. The changes were made expeditiously because it was not a safety-critical process and there were no customer mandates to use a specific approved process. Sure enough, the defect rate plunged. 

About “Non-chemical” cleaning
Media processes are typically referred to as non-chemical cleaning, The concept of cleaning without chemicals is intriguing, particularly in an era where chemicals that work seem to come under scrutiny by regulatory agencies. Examples of non-chemical cleaning include laser ablation, plasma, media, and steam. In truth, most non-chemical cleaning is likely to involve one or more chemicals. Steam is water; water is a chemical. While the chemicals are generated in situ, plasma cleaning involves a complex mixture of chemicals, including free radicles. Safety and environmental issues may be associated with non-chemical cleaning. A notable sign in a research lab reads “DO NOT LOOK DIRECTLY INTO LASER WITH REMAINING EYE.” 

About Media
Media processes are often referred to as deburring, polishing, vibratory finishing – anything but cleaning! There is an astonishing and diverse variety of media. Examples include plastic, gems (e.g. garnets), walnut shells, ceramics, sodium bicarbonate, and steel. Media size varies; the media may be the size of pebbles, sand, or even powder. The process may involve tumbling or blast. As in the example in this article, the parts may be submerged in a tank of media. 

Cleaning with media is not always recognized, even by those in the field. When we suggested a that colleague who supplies micro blast processes contribute a chapter to the “Handbook for Critical Cleaning (1),” his initial response, like that of many suppliers of media, was that media is dirty, dusty. However, after giving the idea some thought, Jawn Swan agreed that the media process removes soil or matter out of place – it’s a cleaning process. Jawn contributed a very useful chapter.

To clean critically, be a preschooler
This anecdote has a number of take-home lessons. Preschoolers are great scientists. They are curious; they are observant; they look at the world with fresh eyes. They ask “why?”. They ask “what’s that?”. You can, too. Sometimes, the solution to surface defects may be simple. The solution to cleaning problems may be hiding in plain sight. 


J. Swan, “Cleaning with Micro Sandblasters,” Handbook for Critical Cleaning, B. Kanegsberg and E, Kanegsberg, editors, 2nd Ed., Vol 1, Chapter 27, CRC Press (2011).

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1 Comment

  1. Miguel Rodas says:

    Hi Barbara and the Rocket Scientist,
    I enjoyed the reading. Indeed, the physical chemistry part of cleaning part before a final finishing is a critical step to avoid/decrease the rate of rejections. I myself have learned a great deal by asking business owners: what’s that? And Why? Thanks for putting the subject of cleaning at the elemental level.

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