Monday, December 19, 2016

Presensitized Printing plate 6

Presensitized Printing plate 6              By Mr. Bob Gumbinner


I took some of the grained and also chemically etched uncoated sheets to both an outfit in Mount Vernon that was anodizing aluminum and an Alcoa plant in Kensington, PA and had them anodized.

We then immersed them in a zirconium fluoride solution and applied the diazo. When imaged and put on a printing press this anodizing treatment the length of run was substantially increased. I therefore worked with Century Engineering to design a line to be able to continuously anodize a web of aluminum. For the anodizing section we contracted with a company that made rectifiers to build two rubber lined tanks with ten foot diameter rubber covered drums. The cathodes were lead pipes that lined the inside of the drums through which cooling water was pumped. The electricity was introduced into the aluminum web by an 18 inch diameter copper roller. First, we used a commutator to connect the roller to the poser supply, later we used carbon brushes. Century Engineering proved the unwind stand; a six brush slurry graining section with rinse and the tanks after the anodizing section to apply the interlayer and rinse and dry. We used the same squeeze roll coating method that we used on the tank line to apply the diazo. This caused the web to wander so we installed an electric eye to adjust the pressure on the squeeze rollers to keep the web in alignment. After a year of operation, the ceramic seal on the shaft of the drums leaked. This was because when the tanks were empty the entire weight of the drum was on the seals. When the 15% sulfuric acid solution was added this lifted the drums up. We then ran this, the B-line, with the sulfuric acid solution only in the lower half of the tank. We obtained sufficient anodizing operating this way.