I posted about this on here a few times, The trick I learned is when you pull ACL Bottles from a dump, a lot of times they are covered in wet moist mud. In these cases you want to let the bottles air dry for a while. the longer the better. At least a month is good. If you try to clean to soon, for example while it's still got the wet moist mud on it good chance the paint will come off. But after a month of drying out, good chance paint will stay intact. In the case of my bottles recently found, I know they been stored under this dry back porch for many years. Possibly since 1959 when these bottles are dated. Thats 60 years of drying. SO, I was pretty confident & not really hesitant of cleaning these, which I did with no problems. Hope this Helps. LEON.
Thanks, leon. I know when i dig them out, its human nature to smear away the mud. However, i have found that just soaking them in hot water for an hour can make the paint come off if i just barely wipe them.