Continuing from part II . . . .
The mirror is rinsed and then soaped. For washing the mirror we use sea sponges that have been treated to remove any particles that may be embedded in the sponges. Sponges are dipped into buckets of soapy water and then squeezed out over the mirror as shown in the photo below.
The mirror is then rinsed again . . .and then re-washed. This time the soapy sponges are lightly brought into contact with the surface of the mirror.
After additional rinsing and an evaluation of the surface reflectivity (improved almost 10% at this point), it is time to remove the old layer of aluminum from the mirror. It is treated with a solution (a mix of Copper Sulfate & Hydrochloric Acid) we call "Green River" that dissolves the aluminum from the disc, taking it from this . . . .
to this . . . .The mirror is then given a dusting of Calcium Carbonate . . .and washed with Potassium Hydroxide and then distilled water.
The mirror is then dried with an industrial paper towel that leaves no particles behind.
To give the mirror its new coating of aluminum it must be carefully lifted . . . .
and placed into the aluminizing chamber.
In case you can't tell, the mirror is hanging on the left side of the image, with the important parts of the aluminizing chamber in the section on the right. I'll describe the process of aluminizing in the next post, part IV.