Methods for Determining Cleanliness

Water-Break Test:

Water will sheet off the part rather than bead

Take a cleaned and dried part and set it in a vertical position.
Use a spray bottle containing distilled water.
Spray the part two to three times from at least 6" away.
If the part is clean and free of oily residue, the water spray should sheet off.
If some oily residue remains, the water will tend to bead on the part

UV Blacklight:

Can you see fluorescence on the parts when viewed using a blacklight?

Take the cleaned and dried part and the blacklight into a dark area.
In the dark area, shine the blacklight onto the part.
If the part is free of soils, it should not highlight any fluorescence
If some soil remains, you should see some florescence where the soil is present.
You should check a dirty part for florescence to ensure that the soil emits a florescence when viewed under a blacklight.

Clean-wipe test:

Will a white cloth remain white after being rubbed on the cleaned part?

Take the cleaned and dried part and wipe it with a portion of a clean, white, lint-free cloth.
If the cloth remains clean, the part is sufficiently clean.
If the cloth becomes soiled or discolored, the part still contains soil residue.

Gravimetric testing:

Will tell how much contaminate is left on the part

Involves filtering a contaminated sample through a control filter and a sample filter.
Place two pre weighed filters, one on top of the other in a single filter holder.
Sample contaminants will be retained entirely by the top test filter.
Both filters are subjected to identical alterations in tare weight as a result of moisture.
Any change in weight of the bottom ("control") filter is then applied as a correction to the weight of contaminant.
Results accurate to 0.1 mg are routinely attained using this method.

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