one impacted and one unimpacted for each primer thickness

[JACEK1]

Hello

What does "one impacted and one unimpacted for each primer thickness" mean?

The fragment below is taken from a painting specification.

4.6.12 Immersion resistance. Thirty-two (nominal) panels shall be prepared as specified 4.5.3. Sixteen panels (eight of each primer thickness) shall be subjected to two impacts from a falling steel ball (see 4.6. 13); the impacts shall be 100 mm (4 inches) apart and equidistant from the edges and sides of the panels. Each of seven wide mouth jars with tightly-fitting caps shall be filled to a depth of 75 mm (3 inches) with one of the following materials:
(a) Grease in accordance with DOD-G-24508. (b) JP-5 jet fuel in accordance with MIL-T-5624. (c) Hydraulic fluid in accordance with MIL-H-83282. (d) Ethyl alcohol in accordance with O-E-760. (e) Aircraft engine turbo shaft lubricating oil in accordance with MIL-L-23699. (f) Detergent in accordance with MIL-o-16791, 0.5 percent solution in synthetic sea water in accordance with ASTM D 1141. (g) Aqueous fire fighting foam in accordance with MIL-F-24385, 10 percent solution in synthetic sea water in accordance with ASTM D 1141.

Four panels , one impacted and one unimpacted for each primer thickness, shall be placed in each jar, each panel resting on its 50 mm (2-inch) side, with one-half immersed and one-half above the teat material. The jars shall be sealed tightly and kept at standard conditions for 4 weeks for all fluids except JP-5 and ethyl alcohol which shall be tested for 24 hours only. Upon removal from the immersion medium, the panels shall be probed with a chisel and compared with the identical untested control panel to detect signs of softening, loss of adhesion, or separation between layers of coating, and otherwise examined for conformance to 3.3.12. The panels immersed in JP-5 and ethyl alcohol shall be allowed a 2-hour recovery period before evaluation. All other panels shall be examined for conformance immediately after removal from the immersion medium.

i haven't the slightest idea.

Thank you.

 

[Charlie Bernstein]

I haven't, either. And what's synthetic sea water? I've heard of man-made ponds. But - man-made oceans?

Is this for real?

 

[GoesStation]

The impacted panels are the ones that have had steel balls dropped on them. Unimpacted is the opposite of impacted; the unimpacted panels have not had balls dropped on them.

This word may have been invented by the author of the specification.

 

[JACEK1]

I still don't understand what "one impacted and one unimpacted for each primer thickness" means, especially what the impacted or unimpacted panels have to do with primer thickness.

 

[GoesStation]

Section 4.5.3 presumably instructs you to paint panels with different amounts of primer. This is the primer thickness.

After dropping balls on the panels you have one impacted panel and one unimpacted one for each of the specified thicknesses of primer.