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exposed layer of entrapped penetrant and disperse it in the thicker layer of developer. Dilution-expansion developers
have a layer thickness equivalent to that of conventional powder developers.
2.8.9
Plastic Film Developers.
Plastic-film developers form a dry, flexible layer that can be peeled or stripped to provide a record of indications on test
surfaces. The most frequently used plastic film developers are two-part systems. The first part provides developer
action while forming a white, reflecting background. The second part forms a clear layer that freezes the indication
and provides film strength and some flexibility. The layers combine and can be removed from the part as a thin film
and maintained as a record of the indication.
