Figure 1-7. Specific Gravity Hydrometer Readings for Two Water Suspended Developers.
Water suspended developers do not perform properly unless they wet the part surface and form a smooth, even coating
when dry. Lumpy or thick areas will hide small indications while uncoated areas will not provide developer action.
Poor wetting is usually due to the addition of too much makeup water to replace drag-out losses or by contamination
with oily materials which destroy wetting agents. It can also be due to developer age, since most of the newer wetting
agents are biodegradable for pollution control purposes. To perform the coating test, use cracked chrome panels;
ensure the panels are clean. Pour or otherwise apply some of the working bath developer and some of the reference
standard developer to the cracked chrome panels and inspect for signs of not wetting, such as pulling apart or forming
beads. The panel should then be dried and examined for even and complete developer coverage.
The developer may also become contaminated with penetrant. Fluorescent penetrant dye contamination can be checked
by visual examination of the bath surface with a black light. Uncontaminated developer appears dull white while
fluorescent dye contamination will show up as specks of yellow-green, floating on the top of the bath.
Testing Water Soluble Developer.
Water soluble developers reduce the number of in-service problems encountered with suspended developers since
agitation is not required and the particles do not settle out. However, there are still concentration and contamination
problems. Evaporation and drag-out will change concentrations during use, and the wetting agents can remove
entrapped penetrant resulting in contamination. Water soluble developer SHALL be periodically tested to assure