Real World Weather Testing

 

An imaged test plate (special blue/black chromic oxide) and two imaged test medallions were placed outside. The medallions were not subject to running water except for rain. The test plate was placed under a running fountain re-circulating particulate laden, brackish water (see effective GPH below). The test plate and medallions were exposed to constant sun (UV) during the day. Part of the test plate was covered with clear tape to protect a portion of the surface (images and background).

The fountain head flow radius was adjusted to cover approximately one sq. ft. The fountain head flow rate was tested using a one gallon container positioned where the water would fall on ½ the test plate. An accurate flow rate of 81.8 GPH (gallons per hour) was recorded. 88.1 GPH translates to 169.42 inches of simulated hard rainfall per hour based on the fact that one inch of rainfall produces .52 gallons of water per square foot.

New Orleans, a city with one of the highest rainfall rates in the country, receives 60 inches per year. That would mean our water flow rate for one hour would equal 2.82 years of rainfall in New Orleans. We ran our test continually for 365 days or 8,760 hours. 8,760 hours x 2.82 years = 24,703.2 years of simulated rainfall based on 60 inches per year. Keep in mind that rainfall does not contain the particulate matter re-circulated in this test. This water was used to see if the images or coating would be eroded under constant small particle bombardment.

Where water continually ran over the test plate there was no appreciable change in color or definition of the images in 8,760 continuous hours. Where the water hit only during a rain (top of the test plate) a build up of a very hard film occurred that was not attacked by mineral spirits, heavy duty detergents, xylene, or peroxide (no out gassing observed). 20% by weight NaOH was used to remove the film build upon completion of the test. No apparent change to the images was observed. Extensive algae build up occurred at times on bottom half of the test plate where the water was constantly running. This was removed periodically with soap using a soft scrub brush. The pieces experienced temperatures ranging from 100 degrees F. to 0 degree F. along with snow and ice. The pieces were outdoors in direct sunlight. No UV degradation to the oxide coating was observed. No film buildup or UV degradation was observed on the medallions.

Please keep one thing in mind. Due to the complexity of the production process each etching of the same subject matter will be slightly different. This is due to many factors. For instance, for the weather test we used two 8” x 8” chromic oxide stainless steel plates on which we imaged eight train photos, each rendered a little differently for lpi and dpi. The same film tool was used to produce each plate, but the results were slightly different from plate to plate. They both looked very good, but we could see subtle differences. The three photos below show the results after the weather test. The top image was photographed from our control plate. It was not subjected to any weather testing. The second image was photographed from our weather tested plate. Both images look good. They are just a little different. Upon close inspection no differences in image definition or UV degradation appeared on the test plate image when compared to the section we had taped before the test began. The tape was still intact after 365 days. No water or particulate matter got under the tape. The tape was removed and the two halves of the image compared. No discernable difference was observed.

Image taken from control plate Image taken from weather tested plate

This was a different image on the test plate, but the right 1/3 of the 8” x 8” test plate was taped (right half of the train image just above). No running water ever touched that portion. The sunlight’s UV could still penetrate.