I love it when I have an epiphany, and can share some great divine wisdom that was bestowed from who knows where.
I have read others suggest they toss their aluminum plates as it was so inexpensive it wasn’t worth the cost of time to clean. In addition, there was a high likelihood of scratches so it became a moot exercise.
I live in Canada, and a piece of 5x7 inch laser aluminum in my neck of the woods costs $5.00 per sheet from my local trophy shop. Due to weight which adds dramatically to shipping costs, it becomes a non-viable exercise to purchase other than local, especially if shipments come north of the 49th parallel.
Therefore, cleaning and re-using is a necessary consideration.
A few days ago I was cleaning my eye glasses and recalled an optician giving me hell for using anything other than appropriate cleaning tissue. I reasoned that if it is good enough for $500 eye glasses, the tissue should surely clean aluminum plates without scratching. It does.
Fill a tray with enough denatured 95% alcohol –the cheaper the better—to cover the plates. Let them soak for 5 or 10 minutes. Using the lens cleaning tissue simply start wiping off the varnish and old image. I was surprised how vigorous one could be without scratching. Let dry on a rack, rinse under hot water, and dry a second time. The plate should now be ready to use ... repeatedly.
There are probably other methods to cleaning aluminum, but I have found this process works beautifully and gives me clean aluminum without a scratch every time.
Should you feel so inclined the money saved can be forwarded to the Dale Wilson Benevolent Fund as a gesture of appreciation. I joke, of course, but give it a try and/or share your process for cleaning aluminum plates.