# 5.2.1.10 Cleanliness

> From: LOCTITE®X Digital Manual for Bonding (https://www.loctitex.com/en/manuals/bonding/5.2.1.10-cleanliness/)

##### 5.2.1.10 Cleanliness

Arguably, the most important consideration of all is the cleanliness of a surface before bonding. Even with proper surface energy, surface roughness and other preparation steps, a contaminated surface will severely hinder the ability of an adhesive to perform properly because adhesives only form bonds with the very top layers of the surfaces to which they bond. Therefore, if the surface of a material is 50% contaminated with fingerprint oils, you could expect to get 50% or less of the performance you would get on a clean surface. In this case, fingerprint oils act as a release agent, providing no adhesive performance at the locations of contamination. Consider the graphic below and the different types of adhesion.

_Figure 135 Adhesion occurs only at the interface of the adhesive and the material occupying the top layer of a substrate. This graphic illustrates how imperfect cleaning may lead to surface contamination and decreased adhesion_

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