Cleaning mirrors for coating is a very exacting process and for larger mirrors it can be physically demanding. The final
step of cleaning and drying the substrate is particularly problematic. Non-contact drying methods, usually with
compressed air or nitrogen, can be laborious and can introduce contaminants if the compressed gas used is insufficiently
pure. These methods also tend to increase the static charge on the substrate surface, attracting lint. Contact methods
tend to add lint or fibers to the cleaned surface. As an alternative, we are experimenting with using the First Contact
polymer cleaning solution as the final step in mirror coating preparation. The advantage of this method is that the
polymer coating, which will adhere to much of the remaining surface contaminants, may be left on the substrate until
just before it is placed into the coating chamber, minimizing the time available for re-contamination. The results of our
experiments on small substrates are presented.
|