T.O. 33B-1-1
2-70
b. They are volatile and fast drying in the air, thus eliminating the need for a drying oven.
c. They are sealed in their containers and are not recovered after their initial use, which eliminates any
degradation, by contamination.
d. When proper techniques are used, they provide a smooth, even layer of developer whose thickness can
be controlled by the operator.
e. Nonaqueous wet developers can be used with both fluorescent and visible-dye penetrants.
f. Nonaqueous wet developers are capable of producing the highest level of sensitivity of any of the
developer forms due to their solvent action.
2.6.6.4
Disadvantages.
WARNING
Nonaqueous wet developers contain solvents that can be relatively flammable, and
when used in confined locations, present a health hazard. Caution must be
exercised to prevent ignition and to avoid inhalation of the vapors.
a. The developer particles are suspended in the solvent and tend to rapidly settle out. Agitation prior to
and during application is required.
b. The portable aerosol containers have a small spray coverage that makes coating of a large surface very
time consuming. The aerosols are best limited to small, local areas.
c. There is a gradual loss of pressure over a period of time and occasionally there are leakers due to
improper sealing. When the pressure is lost the can and its remaining contents must be properly
discarded.
d. If the nozzle is not free of dried developer particles, spray patterns can be very erratic. It is necessary to
clean the nozzle after every use by inverting the can and pressing the spray nozzle until only propellant
escapes.
2.6.7
Developer Dwell.
2.6.7.1
Minimum Dwell Time.
Extraction of the penetrant entrapped in a flaw is a function of time and volume of available penetrant. Time must be
allowed for the developer to assist in drawing some of the entrapped penetrant from the flaw and spreading it on the
part surface to form the indication. The length of developing time varies widely with a number of influencing factors.
The development time SHALL be at least one-half of the penetrant dwell time, and SHALL NOT start until part is
completely free of moisture.
