I have had decorative metal exterior window grids on my windows for 10 years in the Southern Calfornia sun. I just removed the grids and can not get the adhesive lines removed. It appears they were applied with a clear silicone adhesive. I have tried all commerical adhesive removers (goo-off, remove it, etc.) and acetone. I can not get the adhesive removed. Are these lines now permanent? Any ideas? Or, do I need to replace the grids so that I don't have to look at the grid lines? Thanks for any and all suggestions.