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even contamination from cleaning products. Given these risks, it is crucial to understand the standards of cleanliness required to ensure product safety and quality. This brings us to the question: ‘How clean is clean enough?’.
How clean is clean enough? How much to clean to avoid contamination seems subjective and open to interpretation. For discussion, consider that levels of cleaning could be evaluated in three degrees of cleanliness – visually clean, residually clean, or microbially clean. Although these categories of cleanliness are related, each is connected to differing levels of consumer risk. Regulatory bodies charged with ensuring consumer safety have provided some guidance. The following sections will explore each level, the associated risks, and potential solutions.
1. Visually clean ISO provides a cleaning standard for the industry that speaks to “visual cleanliness” in ISO 22716 - 2007: Cosmetics—Good Manufacturing Practices (GMP) [2], where cleaning is described as “separating and eliminating generally visible dirt from a surface” (section 2.8). This standard directs all visual soil to be removed from an equipment surface. Of all types of contamination, this standard seems most straightforward to achieve and confirm; however, in practice, this is not always the case. There can be ambiguity in defining the ‘base state’ or starting point. For example, what if the tank is stained,
rouged, or somehow damaged, such that no one recalls the beautiful silver luster of the new stainless steel? How would one establish a visually clean standard? Tank remediation or passivation could be
performed in a situation like this to return the equipment to a ‘base state’ or a like-new appearance. Alternatively, through testing (residue, microbial) and risk assessment, a quality group and manufacturing group could align on a best-case current state and a new baseline. So, how does one measure visually clean?
Visually clean is a test method requiring a procedure, standardization, and perhaps calibration. Let’s explore three key variables that help define what is considered visually clean: light conditions, surface conditions, and the measurement instrument. Lighting, or lack of light, can affect the
ability to view the surface clearly. Thus, a C&S inspection procedure must include a lighting definition – specifying the light source, bulb type, illumination angle, and so on. Maintenance of that light source could also be necessary, as the condition of the light bulb can deteriorate over time. Sometimes, a preventative maintenance plan for the light source may be necessary. The condition of the surface inspected is
also essential. For instance, a wet surface can appear different from a dry surface and can disguise the presence of soil residue. Thus, the procedure must specify the surface condition, i.e., whether the surface is wet or dry for inspection.
PERSONAL CARE June 2025
Figure 2: Without proper cleaning and sanitization procedures, your equipment is at risk of microbial growth, which may present itself as biofilm on the interiors of your equipment
The operator is the primary ‘instrument’
or test device in a visually clean assessment. An operator must be assessed or qualified as capable of performing the test. Visual acuity, corrective lenses, and the ability to distinguish colors can be crucial in qualifying a technician for a visually clean assessment. Once the capability is established, the technician should be trained in the proper inspection techniques following the written procedure. Once these procedural requirements
are defined, success criteria for the test must be established. Since no numeric test result is tied to visual assessment, a visual standard is necessary to ensure consistent measurement against the success criteria. This is often achieved through a visual standard created with photos of acceptable versus non-acceptable views. Results should be documented following each cleaning. These visual standards support mitigating the risk that accompanies having multiple qualified operators to conduct the visual test. Though paper-based and digital formats are acceptable for housing these procedures, there are many advantages to utilizing a digital format; these advantages include but are not limited to a more interactive and engaging training experience for the operators and robust documentation and historical data traceability for audit readiness.
2. Residually clean Even if the equipment is cleaned to a ‘visually clean’ standard, residues present at levels not visible can impact consumer safety. For instance, some actives, such as chemical sunscreen ingredients, are not visually detectable. Also, detergents can leave residues impacting product quality if not rinsed sufficiently, which may not be detectable by visual inspection. Removing all detectable levels of product,
actives, and detergent to ensure a clean surface is not economical for manufacturers,
as excessive amounts of time and water may be required. Depending on the industry, regulatory agencies may take a risk-based approach, requiring that residues be reduced to a ‘safe level’ for customer use. Often, that safe level is based on a
toxicology assessment, ensuring that the residual quantity carried into the next batch is well below an observable effect or an adverse event level. This requires manufacturers to know the residues that could be present, a safe and acceptable residue level, a test method to verify the residue level, and a cleaning process that reliably removes the product, actives, and detergent to that safe level. A cosmetic manufacturer knows their
formulation, so they know the actives or formulated ingredients that could remain as residue, and the associated activity or toxicity. They typically have a test method already developed for the active ingredient, as they likely test the final formulation to verify it is within specification. That test method may need to be verified or
modified to measure the lower residual actives following cleaning accurately. Frequently, a non-specific test such as the Total Organic Carbon (TOC) test method can verify that non- active formulation ingredients are removed. The greater unknown for cosmetics
manufacturers may lie with the cleaning detergent. A reputable supplier will be able to share the toxicity information for the detergent and appropriate test methods for determining residue. Within the industry, test methods may be specific (identifying the particular chemical component) or non-specific (indicating the presence of a residue but not the particular chemical) based on a toxicity risk assessment. Frequently, detergents used in cosmetics
applications are low-risk and can be tested by non-specific methods. Examples include Total Organic Carbon (TOC), conductivity, pH, etc. In any of these cases, lab work is required to provide a correlation or translation from the non-specific method result to the actual
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